Histology block I

Question 1

What is the first step of a glass histological slide paraffin section?

Answer 1

Fixation with alcohol and acetic acid of formalin for preservation of tissue degradation

Question 2

What is the second step on the histological slides paraffin sections?

Answer 2

Embedded in paraffin or plastic for support of specimen and allows sectioning

Question 3

How thick is the measure of sectioning tissues for histological slides?

Answer 3

~5 - 10 microns

Question 4

Mention the last steps of the glass histological slides preparation

Answer 4

-differential staining for contrast
-dehydration through alcohol series (up to 100%)
-Mount on glass with resin and cover slip

Question 5

What are the advantages of Light microscopy?

Answer 5

-several types [bright field, phase contrast, fluorescent, confocal]
-small and portable
-good for looking at overall arrangement

Question 6

What are the disadvantages of Light microscopy?

Answer 6

-lower resolution, and magnification, less view.

Question 7

Mention the types of electron microscopy

Answer 7

• Transmission electron (TEM)
  -Scanning electron microscope (SEM)

Question 8

What are the advantages of Electron microscopy?

Answer 8

-greater magnification an resolution of detail
-you can see everything

Question 9

What are the disadvantages of Electron microscopy?

Answer 9

-Very large
-preparation of specimens and use of instrument more complex

Question 10

Describe cryo-sections for light microscope

Answer 10

-fixed as paraffin sections
-specimen is frozen
-frozen specimen is mounted on a cryostat and sectioned with a cooled steel knife
-collected on glass slide, thawed, stained with dyes
-dehydrated and mounted under thin glass coverslip

Question 11

Mention the advantages and disadvantages of cryo-sections

Answer 11

advantages:
-much faster and suitable while patient is on operation table

disadvantages:
-preservation of histological structure is more poor due to ice crystal damage, not best quality.

Question 12

Which is the most common staining technique for light microscopy?

Answer 12

H&E (hematoxylin and Eosin)

Question 13

Answer 13

identify the parts in which the Hematoxylin stains are and the Eosin stains are

Question 14

Which charge is Hematoxylin and which charged strcutures does it stain?

Answer 14

positive; negative

Question 15

Which charge is Eosin and which charged strcutures does it stain?

Answer 15

negative; positive

Question 16

Another name for Hematoxylin staining

Answer 16

Basophilic-staining

Question 17

What type of molecules does basophilic staining include?

Answer 17

Phosphate backbones, nuclei, nucleic acids and polyanions

Question 18

What type of molecules does eosinophilic staining include?

Answer 18

collagen, cytoplasm

Question 19

Another name for esosinophilic staining

Answer 19

acidophilic staining

Question 21

how does Trichome stains work?

Answer 21

incorporate 3 or more dyes to give a more complex staining pattern often differentiating tissues or fibrous extracellular components from each other

Question 21

Provide an example of trichome stains

Answer 21

Mallory staining technique

Question 22

Which stain is this?

Answer 22

trichome stain(Mallory staining technique)

Question 23

Which dyes does trichome stain use and what does it stain?

Answer 23

1. Aniline blue
2. acid fuchsin
3. orange G
   selectively stain collagen, cell cytoplasm, and red blood cells these colors.

Question 24

mention this type of stain

Answer 24

light microscopy: Silver/chromium stain

Question 25

what does chromium or silver stains stain?

Answer 25

used to stain some extracellular fibers and some cells in the nervous system and endocrine system

Question 26

Mention this type of stain

Answer 26

Periodic Acid Schiff staining (PAS technique)

Question 27

what does Periodic Acid Schiff staining (PAS technique) stain?

Answer 27

Periodic acid cleaves some of the carbon-carbon bonds in sugars and changes to aldehyde groups which bind the Schiff reagent and stain bright pink. Thus good for some carbohydrates and basement membranes

Question 28

Mention this stains

Answer 28

Examples: Orcein’s elastic stain (brown); Weigert’s elastic stain (blue); Wright and Giemsa

Question 29

What does Orcein’s elastic stain ; Weigert’s elastic stain; Wright and Giemsa stain do stain?

Answer 29

differentiate different types of blood cells

Question 30

Explain step by step how are specimens for transmission electron microscopy, sectioned?

Answer 30

Specimen fixed with glutaraldehyde (crosslinks proteins by aldehyde groups) followed by Osmium metal (fixes lipids)
2.Dehydration of specimen with alcohol or acetone series
3.Infiltration and embedding of specimen with a polymerizable plastic
4.Cutting of section with a microtome with either a glass or diamond knife. The sections are much thinner than for light microscopy (0.1 micron)
5.Mounted on 3 mm diameter copper grid and stained with electron dense heavy metals (uranyl acetate and lead citrate)
6.Examined in electron microscope

Question 31

Which kind of microscope is this?

Answer 31

TEM

Question 32

mention the techniques for specimen fixation used for TEM?

Answer 32

1. freeze-fracture
2. Quick-freeze deep-etch technique

Question 33

Explain step by step how are specimens for freeze-fracture on TEM, sectioned?

Answer 33

1. Specimen infiltrated with a cryo-protective agent such as glycerol to help prevent ice crystal formation and then rapidly frozen by plunging into liquid nitrogen
2. Frozen specimen mounted in a freeze-fracture unit at a temperature of -110 to -120 degrees under vacuum and cleaved (fractured) with steel knife
3. A metal (platinum) replica of fracture face surface is made
4. The specimen is removed and warmed to room temperature and the tissue dissolved away
5. The cleaned metal replica of surface is examined in the transmission electron microscope

Question 34

What is the freeze-fracture technique useful for?

Answer 34

for examining membrane structure

Question 35

Mention the microscope and which structure is this?

Answer 35

TEM; intestinal epithelium cells

Question 36

Explain step by step the quick-freeze deep-etch technique

Answer 36

1. In this procedure the sample is rapidly frozen (-10,000 degrees/sec) without the use of cryo-protective agents. At this speed of freezing water is solidified without the formation of ice crystals which would disrupt structure.
2. Freeze-fracture of the specimen is performed under vacuum maintaining the specimen temperature below -110 to -120 degrees centigrade.
3. The specimen temperature is then raised to -100 degrees for a short time. At this temperature the water at the surface changes to the vapor phase and is removed from the specimen, thus exposing surface detail by etching away the surrounding water.
4. The specimen is rotary shadowed with platinum to form a replica which is cleaned and examined in the transmission electron microscope.

Question 37

Which technique is used here?

Answer 37

Quick-freeze deep-etch technique

Question 38

what does the Scanning electron microscopy (sem) useful for?

Answer 38

has the advantage of allowing a more three-dimensional imaging of cells and tissues.

Question 39

Which microscope was this taken from?

Answer 39

SEM

Question 40

Mention the type of micrograph and all the strcutures you can recognize

Answer 40

Electron microscope;
1. Golgi complex
2. mitochondria
3. Rough eR
4. Smooth eR
5. secretory Vesicles

Question 41

What do membranes do?

Answer 41

Membranes compartmentalize biochemical functions of the cell and form closed compartments within which biochemical reactions take place with minimal interference from reactions in adjacent compartments of the cell.

Question 42

mention type of microscope, structure and function of organelles present

Answer 42

Electron microscope; mitocondria (ATP production); rough endoplasmic reticulum (protein synthesis)

Question 43

Are membranes static?

Answer 43

No

Question 44

Mention the main functions of cell membranes

Answer 44

1. Selective permeability
2. structural scaffolding
   3.vesicular transport
3. division of labor

Question 45

How does selective permeability work and mention examples?

Answer 45

can tightly control the environment such as pH or substrate concentrations within an organelle or region of the cell and thus influence the equilibrium or nature of the biochemical reactions taking place in that organelle; electron transport reaction, H+ act to drive prodcution of ATP, [protons]

Question 46

for what does structural scaffolding work on cell membranes and provide one example?

Answer 46

for enzyme and receptor attachment; hormone receptors

Question 47

how does vesicular transport work on cell membranes?

Answer 47

Forming vesicles to move large particles between cellular compartments

Question 48

What is the division of labor?

Answer 48

In eukaryotic, the concept that cells use membranes to divide their functions into specific compartments for better efficiency

Question 49

Explain this image

Answer 49

Fluid Mosaic Model of Membrane Structure; lipids arranged as a bilayer and proteins floating within the bilayer. Carbohydrate groups (green) are attached to both the lipids and the proteins primarily on the extracellular surface (non-cytoplasmic side) of the membrane

Question 50

How are lipids arranged in the FLMMS

Answer 50

primarily phospholipids with some sphingomyelin and glycolipids) are arranged as a continuous bilayer with their polar head groups on surfaces and fatty acid chains in interior of bilayer

Question 51

How are proteins arranged in the FLMMS?

Answer 51

Proteins float in the lipid bilayer like icebergs. Are present as peripheral proteins loosely attached at surface and integral proteins deeply embedded in bilayer

Question 52

How are carbohydrates arranged in the FLMMS?

Answer 52

Carbohydrate (2 – 5% by weight) is attached on non-cytoplasmic surface to lipids and proteins

Question 53

Describe de bilayer structure

Answer 53

is fluid like a thick oil with many (~50%) of both lipids and proteins able to move in plane of membrane as a mosaic like arrangement.

Question 54

mention the components in this picture

Answer 54

Cholesterol molecule, hydrophobic fatty acid chain, hydrophilic polar (charged) head, non-polar non charged hydrophobic.

Question 55

how are lipid and protein molecules arranged?

Answer 55

arranged to maximize contact of their polar groups (hydrophilic - water loving groups) with water, and to sequester their non- polar groups (hydrophobic - water hating groups) away from water (amphipathic structure)

Question 56

Hows does the temperature affect the fluidity of the membrane?

Answer 56

higher temperature = more fluidity
lower temp = less fluidity

Question 57

Hows does cholesterol affect the fluidity of the membrane?

Answer 57

reduces fluidity

Question 58

Which components play key role in the fluidity of the membrane?

Answer 58

phospholipid composition, fatty acid chain length, saturation or desaturation of the fatty acid chains, temperature, and cholesterol

Question 59

How does fatty acid chains affect fluidity?

Answer 59

Double bond promotes fluidity

Question 60

Mention the components

Answer 60

glycophospholipids, lipid raft, carbohydrates, peripheral protein, peripheral proteins, integral protein

Question 61

what does the lipid bilayer function as?

Answer 61

a permeability barrier

Question 62

How do simple molecules pass the lipid bilayer?

Answer 62

simple difussion

Question 63

Mention some molecules that can pass thru de lipid bilayer by simple difussion?

Answer 63

some gases such as O2 and CO2, small polar molecules such as H2O Etanol, small lipid-soluble molecules and some hydrophobic molecules such as benzene

Question 64

how to charged molecules pass the lipid bilayer?

Answer 64

require integral proteins in the form of channels or carrier proteins to pass across the membrane either by facilitated diffusion (no ATP or additional energy required) or active transport (ATP or other energy expenditure required).

Question 65

mention some molecules that need to pass the lipid bilayer by facilitated difucssion or active transport?

Answer 65

Charged molecules such as most ions, sugars, amino acids, and nucleotides

Question 66

We know that charged molecules pass the lipid bilayer requiring some extra help, but how to they do this, through which structure?

Answer 66

Channels

Question 67

How are the channels of the lipid bilayer?

Answer 67

can be ungated, but often are either voltage- or ligand-gated to open or close

Question 68

mention the types of difussion image

Answer 68

Simple difussion; carrier protein; channel protein; the presence of both carrier proteins and channel proteins
to facilitate movement of large polar molecules across the membrane

Question 69

What are the classes of membrane proteins?

Answer 69

1. Peripheral proteins
2. Integral proteins

Question 70

Explain peripheral proteins

Answer 70

are loosely bound to surface of membrane by electrostatic bonds.

Question 71

can you remove peripheral proteins? yes? no? how?

Answer 71

yes, Easily removed with high ionic strength solutions

Question 72

Peripheral proteins function

Answer 72

Includes some cytoskeletal proteins that anchor to the membrane and are involved in shape determination and membrane stability

Question 73

Explain integral proteins

Answer 73

are tightly bound to the lipid bilayer

Question 74

Can integral proteins be removed? yes? no? how?

Answer 74

require membrane destruction (lipid solvents or detergents) for removal.

Question 75

Mention the subdivision of integral proteins

Answer 75

1. Transmembrane proteins
2. Lipid anchored proteins

Question 76

Explain transmembrane proteins

Answer 76

the amino acid sequences at the membrane surfaces are hydrophilic and those in bilayer are hydrophobic.

Question 77

Explain lipid anchored proteins

Answer 77

covalently linked to lipids but do not extend thru bilayer core

Question 78

mention the structures in terms of proteins

Answer 78

integral membrane proteins
peripheral membrane proteins
lipid anchored proteins

Question 79

What is the main function of integral membrane proteins?

Answer 79

major proteins which act as, ion or carrier protein pumps, ion channels, receptors and signal transducing proteins (such as the G-proteins), structural linkers between cytoskeleton and extracellular matrix, enzymes, and structural proteins

Question 80

Provide examples of integral proteins

Question 81

describe the illustration

Answer 81

Diagram illustrating the important role played by integral membrane proteins which can act as channels, pumps,
receptors, linker-proteins, enzymes, and structural proteins

Question 82

Where are carbohydrates located?

Answer 82

Mainly present on the external surface of the plasma membrane bound to some of the integral proteins and phospholipids as the cell coat or glycocalyx

Question 83

What are the functions of carbohydrates?

Answer 83

They often act as key recognition sequences or receptor components for:
1. Enzymes
2. Hormone binding
3. Virus binding (HIV)
4. cell recognition/diferentiation (for example differences in the carbohydrate groups present on the surface of red blood cells differentiate the A, B, AB, and O blood types)

Question 84

Explain the illustration in terms of carbohydrates

Answer 84

extracellular surface, cytoplasmic surface; Diagram of modified fluid mosaic model of membrane showing the
extracellular location of membrane-associated carbohydrates

Question 85

mention the structure pointed, the tissue where it is located and the type of microscope

Answer 85

EM of microvilli on intestinal epithelial cells showing the glycocalyx
or cell coat

Question 86

What are lipid rafts?

Answer 86

Larger stable regions where some of the proteins and associated lipids are arranged

Question 87

Explain lipid rafts concentrations and where are they present

Answer 87

contain higher concentrations of glycosphingolipids and cholesterol and are present as thicker regions of the membrane.

Question 88

Which is the categorization of how lipid rafts work?

Answer 88

These lipid rafts tend to localize together groups of proteins or lipids involved in a common function

Question 89

In what are lipid rafts involved?

Answer 89

They may be involved in cholesterol transport, endocytosis, and especially signal transduction.

Question 90

provide specific examples of lipid rafts

Answer 90

signal receptor and effector proteins and enzymes may be located together to receive and convey specific signals more efficiently.

Question 91

What are the two major ways to look at membranes?

Answer 91

1. Thin sections in EM
2. Freeze-fracture replicas in EM

Question 92

Identify the structure and the way of looking at it

Answer 92

1. plasma membrane and zonula occludens cell junction
2. Thin section EM image of intestinal epithelial cell

Question 93

Identify the structure and the way of looking at it

Answer 93

1. region of the plasma membrane and zonula occludens
2. Freeze-fracture EM image

Question 94

How is the structure of membranes in thin sections in TEM?

Answer 94

membranes have a trilaminar structure = two dense outer layers separated by an electron translucent central layer

Question 95

How is the thickness of the plasma membrane and the cytoplasmic membrane in thin sections of TEM?

Answer 95

7.5 - 10 nm thick for plasma membrane & 6 - 7.5 nm thick for cytoplasmic membranes

Question 96

Identify the structure and its appearance

Answer 96

Thin-section EM showing the trilaminar appearance
of the plasma membrane on intestinal microvilli

Question 97

Explain this image

Answer 97

Electron dense, electron translucent, electron dense; trilaminar structure of plasma
membrane,

Question 98

Explain how this works

Answer 98

charge distribution contributes to the trilaminar
appearance of the membrane as seen in thin section
EM

Question 99

Explain how freeze-fracture works on TEM?

Answer 99

1. tissue is rapidly frozen (vitreous state – no ice crystals) in cryogen and cleaved with knife edge
2. Half of the tissue is cleaved away and removed in this process
3. The surface of the remaining tissue is coated with a heavy metal to form a replica of the surface
4. The remaining tissue is removed by bleach and the replica examined in the TEM

Question 100

what is the unique feature of freeze-fracture?

Answer 100

the fracture plane tends to preferentially move along and split membranes along the central plane of the bilayer between the phospholipid fatty acid chains with the fracture plane passing around the integral proteins.

Question 101

Name the fracture faces membrane of freeze-fracture

Answer 101

the P-face and the E-face are produced

Question 102

What is the P-face associated with?

Answer 102

associated with the inner leaflet of the membrane adjacent to the cytoplasm (protoplasm).

Question 103

What is the E-face associated with?

Answer 103

associated with the outer leaflet of the membrane adjacent to the extracellular space outside the membrane

Question 104

What are intramembraneous particles? (IMPs)

Answer 104

An important feature seen on the fracture faces is the present of bumps which represent the integral proteins in the membrane

Question 105

Mention the faces and the technique

Answer 105

top: E-face
bottom: P-face

Question 106

Where are IMPs located and why?

Answer 106

In general see more IMPs on the P-face than E-face. This probably correlates with ~50% of membrane proteins being anchored in place by attachment to cytoskeletal structures or other proteins in the cytoplasm

Question 107

Why is the ability of membranes to form closed spherical vesicles so important?

Answer 107

The vesicles and their associated proteins play a major role in the transport of substances into and out of the cell at the plasma membrane, and between organelles in the cytoplasm

Question 108

What are the 3 major types of transport by membrane vesicles?

Answer 108

Endocytosis
Exocytosis
Intracellular transport

Question 109

What is endocytosis? (short)

Answer 109

Is the uptake (internalization) of material by cell from the outer membrane into the cytoplasm

Question 110

What is exocytosis? (short)

Answer 110

Is the release of material out of the cell by secretion

Question 111

What is intracellular transport? (short)

Answer 111

Transport & sorting of proteins or other molecules between the organelles and plasma membrane.

Question 112

Identify the vesicular transports

Answer 112

Exocytosis and endocytosis

Question 113

explain endocytosis in depth

Answer 113

Mechanism for bulk movement of fluids, proteins, or even whole structures such as bacteria into the cell

Question 114

What are the subdivisions of endocytosis

Answer 114

Pinocytosis
Receptor mediated endocytosis
Phagocytosis

Question 115

Explain pinocytosis (short)

Answer 115

bulk intake of extracellular fluid, typically not highly specific

Question 116

Explain receptor mediated endocytosis (short)

Answer 116

highly specific uptake of required substance and usually requires specific receptors for the substance and involves a protein called clathrin

Question 117

Explain phagocytosis (short)

Answer 117

Intake of particles larger than 250 nm in diameter such as bacteria. It can be either relatively non-specific or highly specific

Question 118

Mention the vesicular transport

Answer 118

Pinocytosis

Question 119

Mention the vesicular transport

Answer 119

Rceptor mediated edocytosis

Question 120

Mention the vesicular transport

Answer 120

phagocytosis

Question 121

Explain in depth pinocytosis

Answer 121

(“cell drinking”) is a process for the non-specific (random) uptake of extracellular fluid and material in solution into pinocytotic vesicles at the cell surface

Question 122

Pinocytosis is also known as

Answer 122

cell drinking

Question 123

Pinocytosis is subdivided into:

Answer 123

Micropinocytosis
Macropinocytosis

Question 124

identify the vesicular transport (be specific)

Answer 124

Micropinocytosis

Question 125

identify the vesicular transport (be specific)

Answer 125

Macropinocytosis

Question 126

identify the structure

Answer 126

Em of endothelial cell showing pinocytosis including macropinocytosis

Question 127

briefly describe micropinocytosis

Answer 127

process for uptake of water and substances into vesicles less than 150 nm diameter. Constitutive (continual) process

Question 128

briefly describe macropinocytosis

Answer 128

uptake into vesicles greater than 200 nm diameter. Allows the maximum uptake of fluid and solutes of any of the endocytotic mechanisms

Question 129

describe micropinocytosis in depth

Answer 129

In many cells there is a continuous (constitutive) non-specific formation of small vesicles (less than 150 nm in diameter) which pinch off from the plasma membrane and carry small amounts of fluid & proteins into the cell.

Question 130

Is micropinocytosis specific or non-specific?

Answer 130

non-specific

Question 131

What does non-specific mean?

Answer 131

Does not require specific receptors in the plasma membrane for the ligand and does not involve the coating-protein clathrin

Question 132

Which proteins are involved in the process micropinocytosis?

Answer 132

involves lipid rafts with the proteins caveolin or flotillin

Question 133

Identify the structure and the transport

Answer 133

EM of continuous capillary with micropinocytic vesicles

Question 134

Which proteins are found in all non-muscle cells?

Answer 134

Caveolin 1 and 2

Question 135

Caveolin 1 and 2 can be found in all NON muscles cells except for which?

Answer 135

except neurons and white blood cells

Question 136

Protein specific to muscle cells

Answer 136

caveolin 3

Question 137

What other proteins are found in the micropinocytosis process, in vesicles distinct from caveolin?

Answer 137

flotillin 1 and flotillin 2

Question 138

How does caveolin protein work?

Answer 138

Caveolin forms complexes of 14 – 16 monomers that aid in causing curvature of the membrane to form the vesicle.

Question 139

Is clathrin requires for micropinocytosis?

Answer 139

No, clathrin-independent

Question 140

what is dynamin and what does it do?

Answer 140

Is a gtpase mechanoenzyme involved in the pinching off of the vesicles allowing vesicles to be free

Question 141

Is actin required in micropinocytosis?

Answer 141

Rearrangement of actin microfilaments of the cytoskeleton is not required

Question 142

Does micropinicytosis depend on clathrin or actin?

Answer 142

No, clathrin and actin - independent

Question 143

Is macropinicytosis sprcific or non-specific?

Answer 143

Non-specific

Question 144

What molecules is involved in macropinocytosis?

Answer 144

actin-filament rearrangements

Question 145

How does actin work on macropinicytosis?

Answer 145

to form membrane-ruffles or folds which fold-back to trap large pockets of fluid with the formation of large vesicles greater than 200 nm diameter.

Question 146

Does macropinocytosis require clathrin?

Answer 146

No (clathrin-independent but actin-dependent)

Question 147

Why is macropinocytosis used for and why is it important?

Answer 147

is used by cells to endocytose large amounts of fluid and trapped solutes. And In particular, it is used by cells of the immune system such as macrophages and dendritic cells to trap antigenic material to be processed to initiate immune responses

Question 148

Although macropinicytosis is non specific, what regulates it?

Answer 148

growth factors such as macrophage colony-stimulating factor, epidermal growth factor, and platelet-derived growth factor

Question 149

What is receptor mediated endocytosis?

Answer 149

a highly specific process for the movement of needed substances into the cell

Question 150

How does RME move needed substances into the cell?

Answer 150

by way of binding to specific plasma membrane receptors for that substance and the formation of structures called clathrin coated- vesicles

Question 151

which other proteins are involved in the binding process of the RME?

Answer 151

adaptins

Question 152

How do adaptins work?

Answer 152

bind to recognition sequences of amino acids on the cytoplasmic domain of the receptor (1), and clathrin molecules in turn bind to clathrin-binding sites on the adaptin protein (2).

Question 153

Mention the transport and explain

Answer 153

Diagram of receptor-mediated endocytosis

Question 154

How does clathrin work on the surface of the membrane

Answer 154

acts to provide the force for bending the membrane into the shape of first a clathrin coated pit (2) which deepens and then pinches off with the help of GTPase dynamin (3) as a clathrin coated vesicle free in the cytoplasm

Question 155

Which proteins are released in RME and what happens?

Answer 155

Clathrin & adaptin are released (5 and 6) and the vesicle fuses with early endosomal compartment of the cell

Question 156

Identify the tissue, technique and mechanism

Answer 156

TEM image of plasma membrane prepared by quick-freeze deep-etch technique showing forming clathrin coated pits and vesicles

Question 157

Describe this process

Answer 157

TEM images of thin sections showing stages in formation of a clathrin coated vesicle

Question 158

What is the inherited condition characterized by a decreased ability of cells, particularly liver cells, to remove cholesterol from blood from receptor-mediated endocytosis of low density lipoprotein particles (LDL particles) due to a defect in the LDL-receptor protein and what does it lead to?

Answer 158

Familial Hypercholesterolemia; It is characterized by extremely elevated levels of cholesterol in the blood which can lead to the development of cardiovascular diseases such as atherosclerosis, heart attacks, and valve pathologies which may be fatal. Men with this condition untreated have a ~50% probability of dying from cardiovascular problems by age 50; and women a 30% probability by age 60.

Question 159

Why does Familial Hypercholesterolemia happen?

Answer 159

1) complete loss of the receptor protein
2) or may involve defective binding of the LDL-protein particles at the LDL protein binding site
3) or may result from a mutation in the NPxY binding site for adaptin in the cytoplasmic domain of the protein thus blocking the binding to adaptin and clathrin and internalization by receptor mediated endocytosis

Question 160

What is phagocytosis?

Answer 160

Used for intake of particles such as bacteria which are greater than 250 nm in size

Question 161

By which cells is phagocytosis used and why?

Answer 161

Primarily used by cells of the mononuclear phagocytic System (MPS) such as macrophages and certain white blood cells to uptake bacteria and other antigenic material

Question 162

By what is phagocytosis of bacteria promoted?

Answer 162

by the binding of antibodies or complement fragments to the bacterial surface

Question 163

By what can phagocytosis be triggered also?

Answer 163

Phagocytosis can also be triggered by the presence of pathogen-associated recognition patterns (PAMPs) commonly found on the surface of bacteria or other pathogens

Question 164

Can phagocytosis of inert non-biological materials occur?

Answer 164

yes, material such as carbon, particles, glass particles, and asbestos fibers

Question 165

Explain this diagram

Answer 165

Diagram of phagocytosis for (a ) bacteria and other antigenic material which may be facilitated by binding of antibodies or complement fragments to the surface of the particle and (b) phagocytosis of non-biological particles which does not involve the binding of antibodies or complement fragments

Question 166

How does phagocytosis engulfs particles and what does it form?

Answer 166

by cytoplasmic pseudopod-like processes to form a vesicle containing the particle which is called a phagosome

Question 167

Does phagocytosis require actin, yes, no, why? Is it actin-independent or actin-dependent?

Answer 167

requires rearrangement of actin, phagocytosis is said to be actin-dependent

Question 168

hOW DOES THE PHAGOSOME DIGEST THE MATERIAL? ans what does it form?

Answer 168

The phagosome fuses with a vesicle containing lysosomal enzymes to form a phagolysosome & the particle is broken down by lysosomal enzymes.

Question 169

How is phagocytosis of non-biological particles different from normal phagocytosis?

Answer 169

Phagocytosis of non-biological particles such as glass, carbon particles, asbestos crystals is similar but does not involve the recognition of antibodies, complement fragments, or PAMPs on their surface

Question 170

What is exocytosis?

Answer 170

is the process involved in either the release of secretory material at the plasma membrane or for transport to the endosome

Question 171

Which organelles does exocytosis involve?

Answer 171

This generally involves the formation of proteins in the rough endoplasmic reticulum (RER) which are transported to the Golgi complex in vesicles where the protein can be modified (glycosylation and sulfation or other modifications) and packaged into vesicles for transport either to the plasma membrane or to endosomes

Question 172

Identify the tissue and transport mechanism

Answer 172

Light micrograph of pancreatic cells showing secretory granules in their apical cytoplasm ready for secretion by exocytosis

Question 173

What are the pathways of exocytosis?

Answer 173

constitutive secretion
Regulated secretion

Question 174

Explain consecutive secretion

Answer 174

the vesicles carrying molecules for secretion move continuously from the trans-Golgi membranes to the plasma membrane with no storage in cytoplasm and no signal for release required

Question 175

Provide examples of consecutive secretion

Answer 175

collagen and immunoglobulin antibody secretion

Question 176

Explain regulated secretion

Answer 176

the vesicles carrying the molecules for secretion move from the trans-Golgi to the apical region of the cell where they are stored until secretion is stimulated by a hormone or other factor causing local movement of calcium into cell.

Question 177

Provide examples of regulated secretion

Answer 177

the release of most hormones and pancreatic enzyme release which require specific signals for the secretion

Question 178

What organelle participates in constant recycling?

Answer 178

endosome and plasma membrane

Question 179

Explain briefly intracellular vesicular transport between organelles

Answer 179

Proteins for movement are made in the rER, then go to the golgi stacks, pinch off into a vesicle into another sac. Then , into the trans golgi network, packed and move to the cell surface.

Question 180

Explain the orientation of the plasma membrane protein

Answer 180

in terms of its cytoplasmic and non-cytoplasmic domains is established during the insertion of the protein into the membranes of the rough endoplasmic reticulum. This orientation of the protein is maintained through-out the entire process of vesicular transport of the membrane protein to the plasma membrane.

Question 181

what is the mechanism for fusion of the vesicles with the target organelle membrane and how are these vesicles targeted to the appropriate membrane or organelle with which to fuse?

Answer 181

SNARE mechanism of membrane vesicle fusion which may also provide part of the mechanism for ensuring the vesicles fuse with the appropriate target membranes

Question 182

What is the SNARE mechanism?

Answer 182

the major mechanism for fusion of a vesicle to a target organelle or the plasma membrane and may help targeting to the correct organelle for fusion

Question 183

What does SNARE stands for?

Answer 183

Soluble NSF Attachment Receptor protein

Question 184

What are SNARE proteins?

Answer 184

a small class of at least 30 - 40 proteins associated both with the vesicle (v-SNARE proteins) and the target organelle membrane (t-SNARE proteins).

Question 185

How does SNARE works?

Answer 185

They can interact specifically with each other to facilitate docking of the vesicle to the specific target organelle or plasma membrane and catalyze fusion of the membranes

Question 186

The initial steps in the targetting of an endocytotic vesicle to the endosome involves

Answer 186

1. Formation by receptor mediated endocytosis of a plasma membrane vesicle with a v-SNARE protein (synaptobrevin or other VAMP proteins) associated with the membrane
2. As the vesicle approaches the endosome, a tethering protein will bind to the vesicle and draw it close to the endosome, where Rab GTPase on the vesicle and its receptor on the endosome membrane and the v-SNARE protein on the vesicle and t-SNARE proteins (such as SNAP-25 and syntaxin) on the endosome membrane will specifically interact to form a trans-SNARE docking complex.
3. This docking complex will draw the vesicle and endosome membrane close enough to each other to initiate and catalyze fusion of the membranes at a fusion pore. Once fusion is initiated the SNARE complex will be referred to as a cis-SNARE complex and allow the recruitment of the general fusion proteins NSF and alpha SNAP to the docking complex to disassembly the cis-SNARE complex

Question 187

Explain this illustration

Answer 187

SNARE mechanism. Diagram of steps in vesicle formation, targeting, docking, and fusion of a transport vesicle with the early endodome

Question 188

What is Synaptobrevin/VAMP1 and what does it do?

Answer 188

is a V-SNARE protein in the synaptic vesicle membrane which binds with the T-SNARE proteins syntaxin and SNAP-25 to form the zipper-like SNARE complex to target and bind the synaptic vesicle to the pre-synaptic terminal membrane

Question 189

What other things occur in the process of release of the synaptic vesicles containing neurotransmitters at the synapse

Answer 189

Fusion of the vesicle and release of its contents occurs

Question 190

What does NSF (N-ethylmaleimide sensitive fusion protein) do?

Answer 190

functions to unzip (disassociate the cis SNARE complex) allowing recycling of the vesicle

Question 191

Explain Botulinum and tetanus toxin effects at synapse

Answer 191

1.
The botulinum toxin from Clostridium botulinum is endocytosed into the cytoplasm of the presynaptic neuron at the synapse at the neuromuscular junction where it cleaves synaptobrevin (VAMP) a V-SNARE protein and the T-SNARE proteins Syntaxin and SNAP-25
2.
This blocks the fusion of the synaptic vesicle with the pre-terminal synaptic membrane thus blocking transmission at the neuronal synapse
3.
Tetanus toxin from Clostridium tetani is similar, but is transported to the spinal cord where it translocates to the pre-synaptic terminal of inhibitory neurons where it blocks their ability to inhibit and regulate the activity of the large motor neurons which innervate the skeletal muscles thus leading to the sustained contraction of the skeletal muscles found in tetanus

Question 192

Identify the structures

Answer 192

Eucrhomatin, heterochromatin, nucleolus, nuclear envelope

Question 193

What is chromatin? and provide an example

Answer 193

nuclear material
containing DNA and various
nuclear proteins (e.g. histones).

Question 194

What is the nucleolus?

Answer 194

Site of rRNA
synthesis and contains regulat ory
cell cycle proteins

Question 195

What is th enuclear envelope?

Answer 195

two
membrane system perforated by
nuclear pores.

Question 196

What is the nucleoplasm?

Answer 196

nuclear content
other than chromatin nucleolus.

Question 197

Identify the type of cell

Answer 197

Nerve cell top, bottom inactive cell (lymphocyte)

Question 198

What is euchromatin?

Answer 198

Loosely arranged (dispersed) chromatin so that
DNA can be read and transcribed.

Question 199

is eucrhomatine transcriptionallt active or inactive site of non-ribosolam RNAs (mRNA and tRNA)

Answer 199

Active

Question 200

What is heterochromatin?

Answer 200

Highly condensed chromatin.
Transcriptionally
inactive.

Question 201

What is consecutive heterochromatin and where is it found?

Answer 201

highly repetitive sequences of DNA, packaged in the same regions in different cells. Usually near the centromeres and telomeres.

Question 202

What is facultative heterochromatin and where is it found?

Answer 202

: is not repetitive,
location is different for different cell types. It may
undergo active transcription in certain cells, under
specific conditions.

Question 203

chromatin at the periphery of the nucleus

Answer 203

Marginal Chromatin

Question 204

What are karyosomes?

Answer 204

Discrete bodies of chromatin irregular in size and shape and size that are found throughout the nucleus.

Question 205

Chromatin found in association with the nucleolus.

Answer 205

Nucleolar
associated chromatin

Question 206

How are nucleosomes described?

Answer 206

Beads on a string

Question 207

Identify the structure

Answer 207

Chromatin isolated from interphase
nucleus appears in EM as a thread
30nm thick.

Question 208

Identify the structure

Answer 208

Chromatin that has been experimentally
unpacked and show the nucleosomes
“beads on a

Question 209

What are nucleosomes?

Answer 209

are the smallest units of chromatin and represent the first level of chromatin folding.

Question 210

How long is the length of dna?

Answer 210

about 100,000 times longer than the
nuclear diameter.

Question 211

How are nucleosomes packed?

Answer 211

8 histone molecules (octamer)

Question 212

what are histones?

Answer 212

the principal structural proteins of chromosomes. They form a core structure of 2 units of each of the four types of
histones (H1 H4).

Question 213

What is the genome?

Answer 213

Entire length of DNA (2.5 billion base pairs) packed in all chromosomes. Each region of

Question 214

What is a gene?

Answer 214

Each region of the DNA helix that produces a
functional RNA molecule

Question 215

What is a telomere?

Answer 215

The end of each chromosome is the telomere which shortens with each cell division

Question 216

Whats the role of telomerase?

Answer 216

Telomere length plays an important role in the lifespan of cells.

Question 217

Identify

Answer 217

neutrophil from a female blood smear, Barr body

Question 218

What is a barr body?

Answer 218

discovered in nerve cells of female cats, looks like a drum stick, can tell the sex

Question 219

mention some aneuploidies

Answer 219

Trisomy
21 (Down’s): leads to
mental retardation and congenital
malformations.
Abnormalities
in sex chromosomes
Kleinfelter’s
Syndrome (XXY):
Male phenotype and no
secondary sex characteristics.
Turner’s
Syndrome ( XO):

Question 220

What is cytogenetic testing?

Answer 220

Special fluorescence probes
(FISH technique ) for in situ hybridization
are used. A single fluorescent DNA or a mixture of different probes is
used to produce different colors in each chromosome.

Question 221

Deescribe

Answer 221

Chromatin condensation; protamines replace histones in tightly compacted chromatin

Question 222

Describe

Answer 222

Chromatin condensation; protamines replace histones in tightly compacted chromatin

Question 223

Which proteins houses the nucleolus and what do they do?

Answer 223

nucleolin and nucleostemin ,
which are shuttling proteins that relocalize from the nucleolus to the nucleoplasm.

Question 224

What is nucleostemin?

Answer 224

Nucleostemin is a p53 (tumor supressing protein) binding protein found within the nucleolus that regulates the cell cycle and influences cell differentiation

Question 225

Identify the strcuture

Answer 225

Fibrillar centers, fibrillar material, granular material

Question 226

What are fibrillar centers?

Answer 226

contain DNA loops
of five different chromosomes (13, 14,
15, 21, and 22) that contain rRNA
genes, RNA polymerase I, and
transcription factors.

Question 227

What is fibrillar material?

Answer 227

(pars fibrosa) contains ribosomal genes that are actively undergoing transcription and
large amounts of rRNA.

Question 228

What is granular material?

Answer 228

(pars granulosa): represents the site of initial
ribosomal assembly and contains
densely packed preribosomal particles.

Question 229

What is the nucleonoma?

Answer 229

the network formed by the granular and fibrillar materials .Genes for the ribosomal subunits are localized in the interstices of this network.

Question 230

What is the nuclear envelope?

Answer 230

Membrane barrier that separates
the nucleoplasm from cytoplasm
(encloses chromatin)

Question 231

By what is the nuckear envelope separated?

Answer 231

Separated by a perinuclear cisternal space , which is continuous with cisternal space
of the rough endoplasmic reticulum

Question 232

What perforates the nuclear envelope?

Answer 232

nuclear pores , which mediate the active
transport of proteins between nucleus and cytoplasm.

Question 233

What is th emain fucntion of th enuclear lamina?

Answer 233

Support the nucleus

Question 234

Identify

Answer 234

Electron micrograph of a portion of the nuclear lamina from a Xenopus oocyte. It is formed by intermediate filaments (lamins) that are arranged in a square lattice. The nuclear lamina is a meshwork of
intermediate type filaments.

Question 235

What is the nuclear lamina formed by?

Answer 235

intermediate filaments lamins and lamin
associated proteins. Mainly composed of Lamin A nad lamin C

Question 236

Which protein attaches the fibrous (nuclear lamina) and which are the lamin receptors it interacts with?

Answer 236

orthogonal lattice. Attached via lamin B
protein to the inner nuclear membrane
through its interactions with lamin receptors:
nurim (binds lamin);
emerin (binds lamin A and B;
lamin B receptor (binds lamin B)

Question 237

Identify the strcuture

Answer 237

Fibrous lamina (nuclear lamina)

Question 238

When do lamins dissemble?

Answer 238

during mitosis

Question 239

functions of the nuclear lamina:

Answer 239

The nuclear lamina appears to serve as
scaffolding for chromatin, chromatin
associated proteins, nuclear pores, and the
membranes of the nuclear envelope.
*
Essential for many nuclear activities
including DNA replication and transcription,
it is involved in nuclear organization, cell
cycle regulation, differentiation, and gene
expression. Lamins disassemble during

Question 240

What are laminopathies?

Answer 240

Mutations of lamin and their associated (receptor) proteins cause various diseases called laminopathies. These are tissue specific diseases that affect striated muscle, nerve or skeletal development, and premature aging.

Question 241

provide examples of laminopathies

Answer 241

Emery Dreifuss muscular dystrophy EDMD

Hutchinson Gilford Progeria Syndrome (HGPS),

Question 242

Explain Emery Dreifuss muscular dystrophy EDMD

Answer 242

associated with mutations in either lamins or lamin receptors, characterized by muscle
weakness and wasting in the upper and lower limbs and cardiomyopathy (weakening of heart muscle). The X linked recessive form of EDMD caused by mutations of emerin , whereas autosomal dominant form of
EDMD caused by mutations in lamin A/C proteins.

Question 243

Explain Hutchinson Gilford Progeria
Syndrome (HGPS),

Answer 243

One of the most severe laminopathies, Hutchinson Gilford Progeria Syndrome (HGPS), which is caused by aberrant splicing of the gene encoding for A type lamins and is associated with premature aging.

Question 244

Identify the strcutures

Answer 244

nuclear pores

Question 245

What are nuclear pores?

Answer 245

Array of “openings” (70
to 80 nm) through the nuclear envelope
formed from the merging of the
inner and outer membranes.

Question 246

What is the nuclear pore complex and what does it do? (NPC)

Answer 246

composed of multidomain proteins
collectively referred to as
nucleoporins. Regulate the
passage of proteins
between the nucleus and
cytoplasm.
*
Ribosomal
subunits exported from
nucleolus to the cytoplasm.
Nuclear
proteins imported from
cytoplasm to nucleus.

Question 247

Identify the structure

Answer 247

Nuclear Pore Complex with Freeze Fracture

Question 248

Identify the strcuture

Answer 248

Nuclear Pore Complex Negative Staining Techniques

Question 249

What does the NPC composed of?

Answer 249

NPC is composed of a central cylindrical body placed between inner and outer octagonal rings, each consisting of 8 protein particles.

Question 250

What is Cryoelectron Tomography (CET)

Answer 250

CET is a version of
electronmicroscopy where 3D reconstruction ofa sample (i.e., electron tomogram) is created from 2D images obtained from freeze fracture methods.

Question 251

identify the micgrography

Answer 251

Cryoelectron Tomography (CET)

Question 252

Identify the strcutures

Answer 252

The Nuclear Pore Complex

Question 253

Explain Import NPC, does it require energy?

Answer 253

Large molecules
containing a nuclear localization amino acid sequence
(NLS , Pro Lys Lys Lys Arg Lys Val), can be imported into the nucleus.
*
Labeled NLS
proteins destined to nucleus binds to cytosolic nuclear importin
receptors that directs them to the NPC in a GTP dependent fashion controlled
by Ran Ras like nuclear GTPase signaling.

Question 254

Explain Export NPC

Answer 254

Proteins that
posses the nuclear
export sequence (NES) bind in the
nucleus to exportin and to a Ran
GTP molecule.
*
The
exportin Ran GTP complexes
pass through the NPC into cytoplasm
where GTP is hydrolyzed and the
NES protein is released.
*
The
NPC transports proteins, all
forms of RNA, as well as ribosomal
subunits in their fully folded
configurations.

Question 255

Identify mechanism?

Answer 255

Export (Nuclear Pore
Complex)
*
Proteins that
posses the nuclear
export sequence (NES) bind in the
nucleus to exportin and to a Ran
GTP molecule.
*
The
exportin Ran GTP complexes
pass through the NPC into cytoplasm
where GTP is hydrolyzed and the
NES protein is released.
*
The
NPC transports proteins, all
forms

Question 256

Identify mechanism

Answer 256

Import (Nuclear Pore
Complex)

Question 257

What is the nucleoplasm?

Answer 257

Material enclosed by the nuclear envelope exclusive of the chromatin and the nucleolus.

Question 258

Explain this nuclear alteration

Answer 258

Nuclear alterations in dying cells

Pyknosis
: condensation of chromatin leading to shrinkage of the
nuclei (dense basophilic masses).
*
Karyorrhexis
: is the destructive fragmentation of the nucleus of
a dying cell whereby its chromatin is distributed irregularly
throughout the cytoplasm
*
Karyolysis
: disappearance of nuclei proteins due to complete
dissolution of DNA (increased DNAase).

Question 259

What is necrosis?

Answer 259

Exposure to physical or chemical
environment that causes acute cellular injury and damage to the plasma membrane

Question 260

What initiates necrosis?

Answer 260

This damage may also be initiated by viruses, or proteins called perforins

Question 261

Mention characteristics of necrosis

Answer 261

Rapid cell swelling and lysis are two characteristic features of this process

Question 262

When does apoptosis occur?

Answer 262

Occurs during normal embryologic development or physiologic
processes, such as follicular atresia in the
ovaries Cells

Question 263

How does apoptosis occur?

Answer 263

Cells can initiate their own death through
activation of an internally encoded suicide
program Apoptosis

Question 264

Mention characteristics of apoptosis

Answer 264

Apoptosis is characterized by controlled
autodigestion, which maintains cell membrane integrity thus, the cell dies without spilling its contents and damaging its neighbors

Question 265

Identify cell death

Answer 265

necrosis left apoptosis right

Question 266

identify

Answer 266

This electron micrograph shows an early stage of apoptosis in a
lymphocyte. The nucleus is already fragmented, and the irreversible
process of DNA fragmentation is turned on. Note the regions containing
condensed heterochromatin adjacent to the nuclear envelope
b.
Further fragmentation of DNA. The heterochromatin in one of the
nuclear fragments (left) begins to bud outward through the envelope,
initiating a new round of nuclear fragmentation. Note the reorganization
of the cytoplasm and budding of the cytoplasm to produce apoptotic
bodies.
c.
Apoptotic bodies containing fragments of the nucleus, organelles, and
cytoplasm. These bodies will eventually be phagocytosed by cells from
the mononuclear phagocytic system. (Courtesy of Dr. Scott H.
Kaufmann.)

Question 267

Identify

Answer 267

This photomicrograph taken with light microscopy of intestinal
epithelium from the human colon shows apoptotic bodies (AB) within a
single layer of absorptive cells.

Question 268

Identify structure and protein stain

Answer 268

Breast cancer cell
Orange: Microtubule marker
Purple: Actin microfilament marker marker

Question 269

What is the cytoskeleton?

Answer 269

The cytoskeleton is a network of protein filaments and tubules in the cytoplasm composed of 3 types of non-membranous filamentous organelles

Question 270

Mention the non-membranous filamentous organelles that compose the cytoskeleon

Answer 270

microfilaments
intermediate filaments
microtubules

Question 271

What is the diameter of the microfilaments and its protein?

Answer 271

6-8 nm diameter & actin is the main protein

Question 272

What is the diameter of the intermediate filaments and its proteins?

Answer 272

are 10 nm diameter & are composed of intermediate filament proteins (several classes of proteins

Question 273

What is the diameter of the microtubules and its proteins?

Answer 273

24 nm diameter & tubulin (α and β
tubulin) is the main protein

Question 274

What is one of the major key roles of the cytoplasm?

Answer 274

cell shape determination and motility

Question 275

Identify the structure, type of micrograph and protein

Answer 275

Fluorescently light micrograph with the distribution of intermediate filaments in fetal lung fibroblasts cells in culture/ Red=vimentin (intermediate filaments)
green=actin

Question 276

Identify the structure, type of micrograph and protein

Answer 276

Fluorescent staining of microtubules with (green) and nucleus in blue. gren= immunostaining for microtubules (tubulin)

Question 277

What is cytomotor function of the cytoskeleton?

Answer 277

movement: of whole cell, organelles, cilia, chromosomes (spindle formation) (mt), and the processes of cytokinesis (mf), endocytosis, exocytosis, cytoplasmic streaming [release of vesicles]

Question 278

What is cytosekeletal function of the cytoskeleton?

Answer 278

involvement in cell shape determination; shape of cilia and microvilli

Question 279

Identify strcuture, tissue, cell shape

Answer 279

Micrograph of non-distended transitional bladder epithelium. Note top balloon-shaped (umbrella or dome) cells or columnar/cuboidal-like shape cells in the bottom

Question 280

Identify strcuture, tissue and protein

Answer 280

EM micrograph of intestinal microvilli supported by actin microfilaments.

Question 281

Identify structure, tissue and region

Answer 281

Tracheal epithelium showing cilia on apical
surface supported by microtubules forms these motile cilia

Question 282

WHat does tubulin have in common in both cytoskeletal functions?

Answer 282

tubulin in cilia helps maintain the long linear shape of the cilium but also plays a key role in the movement of the cilia

Question 283

Identify strcuture, function

Answer 283

tubulin maintains the shape of the colium in this oviduct and helps with the moevment of ciclia to move the oocyte along the oviduct

Question 284

Identify strcuture, function

Answer 284

Micrograph of cerebellum showing the very asymmetrical shaped Purkinje cells with dendrites

Question 285

Identify strcuture, function

Answer 285

EM image of a mature myelinated axon showing microtubules in the cytoplasm

Question 286

Explain correlation of cytiskeleton in purjunkie neurons of cerebellum

Answer 286

cytoskeleton plays a role both in maintaining very asymmetric shape of Purkinje neurons in cerebellum (structural function), but also within axons plays a key role in fast axonal transport of molecules and organelles to axon terminal (motor function)

Question 287

How is actin called in its unpolymerized and polymerized form?

Answer 287

G-actin (Globular), while in its polymerized form (the filament) it is called F-actin (Filamentous

Question 288

What is the strcuture of the filament of actin?

Answer 288

double helical arrangement

Question 289

describe structure and stain

Answer 289

Electron micrograph of actin (negative stain)

Question 290

describe structure and stain

Answer 290

computer filtered image of actin filament, and diagram of double helical structure of actin filament

Question 291

Mention functions of the microfilaments

Answer 291

Anchorage and movement of membrane proteins = focal adhesion point
Formation of the structural core of microvilli and stereocilia
*
Locomotion of cells – thought to involve a reversible gelation - solation of cytoplasm & may involve myosin II (thick filaments) and or myosin I
*
Extension of cell processes – filopodia & lamellipodia
*
Vesicular transport and movement of organelles (myosins I, II, Va, Vb, VI, VIIa, IXa, X)
*
Cytokinesis
*
Morphogenetic movements of tissues during embryology e.g. shaping of epithelia into tubes and etc

Question 292

What are focal adhesion points?

Answer 292

Points where you have actin filaments intercating with integrins and integrins interacting with the extracellular matrix; scaffolds for signaling pathways

Question 293

Why is polymerization and depolymerization of actin microfilaments important?

Answer 293

There is a large pool of G-actin in the cell in equilibrium with the F-actin. This allows microfilaments to be polymerized and depolymerized in specific areas of the cell as necessary for function

Question 294

What does actin polymerization require?

Answer 294

requires the hydrolysis of ATP

Question 295

On what does actin polymerization depend on?

Answer 295

depends on the local concentration of G-actin (binds to ATP) & other actin-binding proteins.

Question 296

Explain briefly polymerization of actin

Answer 296

The polymerization occurs as a polarized process in which G-actin molecules with bound ATP bind preferentially at the (+)-end of the filament. After a short time the bound ATP is hydrolyzed to bound ADP, and eventually the actin with bound ADP is lost by depolymerization at the (-) end of the filament. This is an ongoing process which has certain proteins to stop it.

Question 297

Which process is this?

Answer 297

Polymerization of actin
filaments

Question 298

What is treadmilling?

Answer 298

the name given to this process in which new actin molecules add preferentially to (+) end filament, while other actin molecules are lost at (-) end thus giving a continuous flow actin from (+) end to (-) end

Question 299

explain the diagram

Answer 299

Pulse-Chase Experiment Showing Treadmilling. Labeled actin molecules (green) add at the plus end of microfilament and after a short period of time the labeled molecules in solution are replaced with non-labeled actin and the patch of labeled actins can be seen to move along the filament

Question 300

Where does treadmilling play a key role?

Answer 300

in motility

Question 301

Mention Drugs That Interfere with the Polymerization and Depolymerization of Actin Microfilaments

Answer 301

Cytochalasins B and D; Phalloidin

Question 302

How does Cytochalasins B and D interfere with the Polymerization and Depolymerization of Actin Microfilaments

Answer 302

These drugs bind (+) end of microfilament & block addition of new actin molecules. Thus the drugs can block cellular activities that require polymerization of the microfilaments, such as cell movement and cytokinesis

Question 303

How does Phalloidin interfere with the Polymerization and Depolymerization of Actin Microfilaments

Answer 303

This drug stabilizes microfilament structure & prevents depolymerization. Thus blocks cell activities requiring reversible polymerization & depolymerization such as cell movement and cytokinesis

Question 304

how does cytochalasis b,d and Phalloidin interefere?

Answer 304

These drugs disrupt the equilibrium between G-actin and F-actin. Because drugs block mitosis by inhibiting cytokinesis they may have anti-tumor use. The drugs also inhibit such cellular activities as lymphocyte migration, phagocytosis

Question 305

How is actin arranged in the cell?

Answer 305

As a loose meshwork of crosslinked filaments or as bundles of parallel filaments

Question 306

Where is the loose meshwork of crosslinked filaments of actin found in the cell?

Answer 306

typically found immediately under and attached to the plasma membrane or as a loose meshwork throughout the cytoplasm.

Question 307

Which crosslink proteins are often associated with te actin filaments in loose meshworks?

Answer 307

Filamin and spectrin

Question 308

Which proteins crosslink with the bundles of parallel filaments in the actin arrangement?

Answer 308

fimbrin or villin

Question 309

Identify the structure and the actin arrangement

Answer 309

Electron micrograph (EM) showing microvilli at apical surface of cell as finger-like projections with a core consisting of a bundle of actin
filaments (terminal web)

Question 310

Identify the structure and the actin arrangement

Answer 310

A higher magnification micrograph (EM)
showing microvilli at apical surface of cell as
finger-like projections with a core consisting of
a bundle of actin filaments

Question 311

Identify the structure and the actin arrangement

Answer 311

core bundle; loose meshwork; EM of cell prepared by quick-freeze deep-etch technique
showing microvilli with core bundle of actin filaments and actin filaments as a loose meshwork in cytoplasm below microvilli

Question 312

Identify the structure and the actin arrangement

Answer 312

Distribution of actin filaments in pulmonary
artery cells in culture.
Green= imunostaining of actin stress fibers (bundles of crosslinked microfilaments)
red=imunostaining of mitochondria

Question 313

How much % of protein does actin make?

Answer 313

10%

Question 314

How does actin microfilament facilitate the binding of a multitude of different proteins

Answer 314

Actin is extremely conserved in its amino acid sequence

Question 315

Mention proteins that can help the filament carry out its function

Answer 315

crosslink filaments into loose gel (filamin)
*
fragment filaments (gelsolin)
*
bundle filaments into bundles (villin, fimbrin, espin)
*
interact with actin to produce motion including vesicular transport (myosins I, II, Va, Vb, VI, VIIa, IXa, X)
*
cap filament ends (example gelsolin) [prevent filament from linking polymerization or shortening length by depolymerization]
*
attach filaments to cell membrane (spectrin, myosin I, ezrin)
*
sequester actin monomers to prevent filament formation (profilin & thymosin)

Question 316

Which myosin is found in the muscle and what does it do?

Answer 316

myosin II; involved in muscle contraction; however there are approximately 35 of unconventional myosins invovled in vesicular transport and movement of other cargo such as organelles

Question 317

Which myosins are associated with vesicular transport and endosomal vesicles?

Answer 317

myosins V and VI

Question 318

Why is myosin VI of extreme interest?

Answer 318

it moves in a retrograde direction towards the (-) end of the actin filament unlike all other known myosins. Thus bidirectional transport by myosins on actin filaments is possible

Question 319

What does tubulin do in these movement of vesicles and other cargo by unconventional myosins V and VI

Answer 319

transports long distances

Question 320

How is the movement along the actin-filaments in areas that lack microtubules and provide example?

Answer 320

often short-range motion, such as under the plasma membrane

Question 321

What is the measurement of microtubules and its key role?

Answer 321

24 nm in diameter. Play a role in both cytoskeletal and cytomotor functions

Question 322

Identify structure

Answer 322

EM micrograph of microtubules in the mitotic spindle of a dividing cell.

Question 323

What are MAPs of MW 50,000 – 300,000 daltons?

Answer 323

microtubule associated proteins involved in many functions

Question 324

Mention the functions of cytoplasmic microtubules?

Answer 324

Intracellular vesicular transport and organelle movement– for example as in fast axonal transport
*
Maintenance of cell shape
*
Movement of cilia and flagella
*
Cell elongation and movement (cell migration)
*
Chromosome movement (spindle formation and pulling chromosomes to poles)
*
Maintenance of position of ER and intermediate filaments (if disrupt microtubules, then get a shift in position of both endoplasmic reticulum and intermediate filaments)

Question 325

What are microtubules composed of?

Answer 325

Composed of tubulin  -  dimers arranged in 13 -15 protofilaments.

Question 326

By what are cytoplasmic microtubules disrupted?

Answer 326

cold, pressure, or high levels of calcium

Question 327

Does actin containing microfilaments have polarity, if so where?

Answer 327

yes, in the cytoplasmic microtubules

Question 328

Where do the tubulin alpha-beta dimers align?

Answer 328

align in a head to tail conformation along the protofilaments. Thus the two ends of the microtubule are different

Question 329

Is polymerization of microtubule polar or non polar? why?

Answer 329

polar with tubulin dimers with bound GTP preferentially binding at the plus end of the microtubule and loss of the tubulin dimers being promoted when the tubulin has bound GDP.

Question 330

Which proteins add to the stability and blocking lengthening & shortening of cytoplasmic microtubules?

Answer 330

Capping proteins and other bound proteins

Question 331

what is the equilibrium of cytoplasmic microtubules?

Answer 331

dynamic equilibriuk (dynamic stability) between assembly and disassembly.

Question 332

what correlates to tje rapid shortening and lengthening of the microtubule?

Answer 332

the state of the nucleotide bound to the tubulin dimer with bound GTP = assembly at plus end and bound GDP = dissociation)

Question 333

Mention drugs that interfere with microtubules

Answer 333

Colchicine, Taxol, Vinblastin & vincristine

Question 334

How does Colchicine interfere with microtubules? and what is it used for?

Answer 334

binds tubulin dimers & blocks their addition to tubule end causing rapid depolymerization of the microtubules. Is used for treatment of some cancers and gout arthritic symptoms. For gout it acts by blocking the movement and function of immune cells in the areas of inflammation in the joints.

Question 335

How does Taxol interfere with microtubules? and what is it used for?

Answer 335

binds to tubulin in the intact microtubule & stabilizes the microtubule. Is used in therapy for breast cancer (very toxic)

Question 336

How does vinblastine & vincristine interfere with microtubules? and what is it used for?

Answer 336

bind microtubule dimers and increase their binding to each resulting in the formation of paracrystalline deposits of the dimers thus reducing the ability of microtubules to polymerize. Are used in the treatment of leukemia and various types of lymphomas in particular. (stabilizes too much, if you stabilize too much or destabilize it affects either way)

Question 337

How do drugs that interfere with microtubules treat cancer?

Answer 337

used as anti-mitotic and anti-proliferative drugs in cancer therapy because they can block mitotic activity through their action on the polymerization and depolymerization of microtubules (can be highly toxic)

Question 338

Explain the polarity of microtubules

Answer 338

There is polarity in the arrangement of the ends of the microtubule in the cell.

Question 339

With what are the (+) and (-) ends associated regarding microtubule polarity and what are the exceptions?

Answer 339

In most cells the (-) end of the tubule is associated with the mitotic organizing center (centrioles) near nucleus & microtubules grow & radiate out with (+) end toward cell periphery. The exception is that in dendrites of neurons they may have opposite orientation. In axons these have a typical orientation.

Question 340

In microtubules of nervous tissue (dendrites) where is the (+) located?

Answer 340

near the nucleus

Question 341

identify the strcuture and the polarity

Answer 341

Immunolabeled microtubules growing outwards from mitotic organizing center (centrioles) with (-) end at center and (+) end peripherally

Question 342

why is polarity so important in microtubules?

Answer 342

important in determining how cytomotor proteins bind microtubules and produce movement.

Question 343

Which proteins move towards the (+) end and which move towards the (-) end?

Answer 343

(kinesins) move toward the (+) end
& others (cytoplasmic dyneins) toward the (-) end

Question 344

given the polarity of microtubules, they are said to give which type of movement to organelles, vesicles and molecules?

Answer 344

bidirectional movement

Question 345

Mention How many types and classes of kinesis and dyneins are there?

Answer 345

kinesins (40 types in 14 classes) and dyneins (9 heavy chain classes)

Question 346

What do kinesins and dyenins represent and what are they invovled in?

Answer 346

represent families of proteins with many distinct members and are involved in a variety of movements including fast axonal transport, chromosome movement during mitosis and meiosis, movement of cilia and flagella.

Question 347

Identify strucutres

Answer 347

Immunostaining showing the presence of a kinesin (Eg5 – red staining) which interacts with polar spindle fibers from the two mitotic poles to help separate the chromosomes. Dynein (not stained) also acts by binding at kinetochores and drawing chromosomes towards poles; chromosomes are shown in the middle

Question 348

What is an example of retrograde transport virus?

Answer 348

Rabiesvirus is transmitted through direct contact (such as through broken skin or mucous membranes in the eyes, nose, or mouth) with saliva or brain/nervous system tissue from an infected animal. People usually getrabiesfrom the bite of a rabid animal.

Herpes simplex virus may use retrograde transport

Question 349

How is rabies virus mechanism retrograde mechanism and its symptoms?

Answer 349

Evidence has been shown that the rabies virus is transmitted along neuronal axons from near the site of the bite to the brain by retrograde transport involving binding of the P protein from rabies virus to the dynein light chain protein LC8.

In the brain, rabies causes acute inflammation of the brain leading to extremely aggressive and violent behavior and death if not treated

Question 350

What is the diameter of intermediate filaments?

Answer 350

10-12 nm

Question 351

wHAT IS THE MAIN FUNCTION OF INTERMEDIATE FILAMENTS?

Answer 351

provide a cytoskeletal (structural, support). They provide mechanical strength and control cytoplasmic stiffness in individual cells, provide mechanical strength to layers of cells, help to control cell shape, and may play a role in the positioning of organelles in the cell

Question 352

Identify

Answer 352

EM showing
hemidesmosomes at the base of
an epidermal cell. The filaments are
Keratin-containing Intermediate
filaments

Question 353

Identify

Answer 353

EM showing a
desmosomal junction (intercellular)
with intermediate filaments (arrows [zonula occludens]

Question 354

Mention the first 2 classes of intermediate filaments proteins

Answer 354

Keratins (epithelia) –tonofilaments

Question 355

mention class 3 intermediate filaments proteins

Answer 355

Vimentin & vimentin-like proteins including desmin (muscle) & glial fibrillary acidic protein (glial cells in nervous system) & several less well known proteins

Question 356

Mention class 4 intermediate filaments proteins

Answer 356

Neurofilament protein (neurons)

Question 357

mention class 5 intermediate filament proteins

Answer 357

Lamins (nucleus - all eucaryotic cells)

Question 358

Mention class 6 intermediate filament proteins

Answer 358

Beaded filaments – (eye lens fiber cells)

Question 359

What is a way of determining origin of cancers and tumors?

Answer 359

Antibody labeling of the different classes of intermediate filament proteins (particularly the different subclasses of cytokeratins

Question 360

Identify clinical correlation and strcuture

Answer 360

For example this image shows astrocytes, a type of glial cell (supporting cell) in the brain immunostained for glial fibrillary acidic protein (GFAP) in their intermediate filaments.
A tumor in which the intermediate filaments of the cells are immuno-stained with GFAP would suggest the tumor is of glial cell origin.
Similarly, immunostaining of the intermediate filaments with an antibody to keratins would suggest an epithelial origin.
Section of brain immuno-stained for glial fibrillary acidic protein
(GFAP) showing astrocytes (a type of glial supporting cell) stained because
their intermediate filaments contain GFAP

Question 361

How are intermediate filaments assembled?

Answer 361

assembled from a pair of helical monomers that twist around each other to form coiled-coil dimers. Intermediate filaments are assembled in a dense ring around the nucleus and then radiate out toward the cell periphery.

Question 362

Do intermediate filaments have polarity? yes? no? how does it affect?

Answer 362

No polarity, it is difficult for a protein to walk into a direction due to no polarity no (+) end

Question 363

How does the non-polarized unit of the intermediate filament come along?

Answer 363

Intermediate filaments are assembled from a pair of helical monomers that twist around each other to form coiled-coil dimers. Two of these dimers then assemble with each other in antiparallel fashion (parallel but pointing in opposite directions) to generate a staggered tetramer of two coiled-coil dimers, thus forming the non-polarized unit of the intermediate filaments. Each tetramer then binds to other tetramers staggered relative to each other along the axis of the filament to form a protofilament, 8 of which are crosslinked to form the intermediate filament

Question 364

How are intermediate filaments assembled in some epithelial cells?

Answer 364

they attach at cell junctions such as hemidesmo-somes and desmosomes and extend as bundles across the cytoplasm from junction to junction

Question 365

Which are the least understood of the cytoskeletal filaments in function?

Answer 365

Intermediate filaments

Question 366

Are intermediate filaments stable or dynamic structures, why?

Answer 366

Although previously thought to be stable structures, they are now considered to be dynamic structures which form filamentous linkages between the cell surface and the nucleus that change depending upon the mechanical stresses on the cell.

Question 367

What are iNTERMEDIATE FILAMENTS important regulating what?

Answer 367

important regulators of the intracellular changes in cytoplasmic mechanics that accompany various physiological activities such as cell contraction, migration, proliferation, and organelle positioning

Question 368

What do intermediate filaments provide?

Answer 368

They provide stiffness and strength to individual cells and help the cells resist and respond to environmental stresses. maintain location of organelles within the cell

Question 369

What do intermediate filaments provide in epithelia and how?

Answer 369

help to strengthen an entire layer of cells. Thus providing a mechanism in which tension or pulling forces on the cells are shared by all the cells thus providing strength to the layer.

Question 370

What are lamins in intermediate filaments

Answer 370

How IF provide strength to the nuclear envelope

Question 371

are intermediate filaments involved directly in motility? why or why not?

Answer 371

No; due to their lack of a polar structure which hinders cytomotor proteins binding to them and moving along the filaments in only one direction.

Question 372

Although intermediate filaments are not directly involved with motility, what are they involved that is important additionally?

Answer 372

rearranged during cell motility & may be involved in controlling directionality of the movement of the cell, and may play a role in the formation and directionality of cytoplasmic processes in cells such as astrocytes.

Question 373

Explain the The Epithelial-Mesenchymal Transition (EMT) clinical consideration and its significance

Answer 373

During embryological movement epithelial cells undergo a process called the epithelial-mesenchymal transition in which the epithelial cells undergo a change to a more mesenchymal-like cell morphology. A key feature of this process is that the intermediate filament composition changes from cytokeratin-containing intermediate filaments to vimentin-containing intermediate filaments and the breakdown of desmosomal and hemidesmosomal junctions. The cells then assume a more mesenchymal – fibroblast-like morphology and become motile.
The clinical significance of this is the finding that epithelial cells becoming cancerous typically recapitulate this epithelial-mesenchymal transition to become motile and metastatic. Evidence has been shown for example that vimentin expression is required for the invasive behavior and metastasis of both prostate and breast cancer cells

Question 374

Mention the proteins which bind intermediate filaments

Answer 374

Filaggrin
Plectin family of proteins
Plakins
Lamin-Associated Proteins

Question 375

what does Filaggrin do in IF?

Answer 375

binds keratin filaments into bundles

Question 376

What do plectin family of proteins do in IF?

Answer 376

bind microfilaments, microtubules, and intermediate filaments into 3-D networks

Question 377

What do plakins do in IF?

Answer 377

involved in binding of intermediate filaments to hemidesmosomes and desmosomes. They also bind actin filaments to the neurofilaments in sensory neurons. Includes desmoplakins, desmoplakin-like proteins, and plakoglobulins

Question 378

What doe lamin-associated proteins do in IF?

Answer 378

Emerin, lamin B receptor, nurim, and other lamin-associated polypeptides [serve to form the fibers coding on the inner surface of nuclear envelope]

Question 379

Identify

Answer 379

Schematic of 3D structure of the G-actin with ribbon representation

Question 380

What is filopodia?

Answer 380

slender cytoplasmic projections that extend beyond the leading edge of lamellipodia in migrating

Question 381

What is lamellipodia?

Answer 381

cytoskeletal protein actin projections that occur at the leading edge of the migratory cells.

Question 382

Identify

Answer 382

filopodia, lamellopodia

Question 383

What is apical and what is basal?

Answer 383

apical is to the outside and basal is close to the base or connective tissue.

Question 384

What is the endoplasmic reticulum?

Answer 384

Membrane bound closed system of
anastomosing tubules and broad flat
saccules called cisternae

Question 385

With what is the ER continuous with?

Answer 385

the outer membrane of the nuclear envelope

Question 386

mention the main functions of the smooth endoplasmic reticulum (sER) and where is it welld eveloped and which enzyme related to it?

Answer 386

principal organelle involved in detoxification and conjugation of noxious substances. It is particularly well developed in the liver and
contains a variety of detoxifying enzymes related to cytochrome P450 into
sER plasma membranes.

Question 387

Whih compouds does the sER detoxify and how?

Answer 387

They modify and detoxify hydrophobic compounds such as pesticides,
barbiturates and carcinogens converting them into water-soluble conjugated
products that can be eliminated from the body

Question 388

Mention other functions of the sER

Answer 388

-lipid and steroid metabolism,
-glycogen metabolism, and calcium homeostasis.
-membrane formation and recycling

Question 389

Mention other enzymes associated with the sER

Answer 389

hydrolases, methylases, glucose-6-phosphatase, ATPases

Question 390

Idenfity structure

Answer 390

The ER Network

Question 391

identify structure

Answer 391

Heat shock protein 90 B-1 antibody (green):
HSP90B1, ER protein resident required for
the folding of numerous signaling proteins

Question 392

What is the sER?

Answer 392

Consists of short anastomosing tubules that are not associated withribosomes.

Question 393

What do large amounts of sER contribute to?

Answer 393

cytoplasmic eosinophilia (acidophilia)
when viewed in the light microscope.

Question 394

Identify strcutures

Answer 394

Abundant smooth ER in a steroid-hormone-secreting cell. This electron micrograph is of a
testosterone-secreting Leydig cell in the human testis. Can see the cisternae

Question 395

identify structures and function

Answer 395

Electron Microscopy (EM) image of abundant sER usually present in cells with active lipid synthesis. detoxyfication

Question 396

How is the sER called in the muscle?

Answer 396

sarcoplasmic reticulum a specialized ER

Question 397

Whats the function of the sarcoplasmic reticulum?

Answer 397

Its function is essential in the process of muscle contraction. In basal state (no contraction) it sequesters Ca+2 from the
cytoplasm. for movement.

Question 398

Where is the sarcoplasmic reticulum located?

Answer 398

The sarcoplasmic reticulum is close to the plasma membrane invaginations that conduct the activating impulses, which trigger the release of Ca+2 and produce the contraction

Question 399

Identify the sarcoplasmic reticulum

Answer 399

blue web

Question 400

identify structure and function

Answer 400

Rough endoplasmic reticulum (rER). A region of the endoplasmic reticulum that is associated with ribosomes and is thus the organelle in which the synthesis of proteins takes place
(proteins destined for export, to a specific organelle or to the plasma membrane)

Question 401

What staining does the rER has and why?

Answer 401

The RNA in the ribosomes has basophilic staining. Therefore, the rER has a basophilic staining pattern.

Question 402

Identify structure and satining

Answer 402

Pancreatic acinar cells; lumen and basophilic staining rER; the clear part is acidophilic staining

Question 403

What is the portion of the cytoplasm that has basophilic staining, called?

Answer 403

ergastoplasm

Question 404

identify structure and staining

Answer 404

Light micrograph of nerve cells (H&E) with Nissl bodies. Nerve cells have large basophilic bodies aclled nissl bodues (rER + many free ribosomes)

Question 405

identify structure

Answer 405

Electromyograph of nerve cells showing abundant rER

Question 406

identify structures

Answer 406

chief cell = secretory cell. Electron micrograph of rER in a chief cell of the stomach
shows membranous cisternae “C” closely packed in “parallel arrays”. The particles attached to the exterior surface of the
membrane are ribosomes

Question 407

Short description of ribosomes?

Answer 407

the protein making machine

Question 408

What are ribosomes and where are they made?

Answer 408

Small particles 15 to 20 nm in diameter and contain ribosomal RNA and protein (made in nucleoulus)

Question 409

What is the ribosomal small subunit?

Answer 409

(40S): 1 RNA molecule + 33 proteins

Question 410

What is the ribosomal large subunit?

Answer 410

(60S) binds to membrane of rER: 3 RNA molecules + 49 proteins

Question 411

How can a ribosome participate in protein synthesis?

Answer 411

associating with mRNA

Question 412

What are polyribosomes?

Answer 412

polysomes = clusters of 10-20 ribosomes

Question 413

What do polyribosomes in the cytoplasm do?

Answer 413

synthetize proteins that remain in the cytoplasm.

Question 414

Identify structure

Answer 414

spiral shaped polyribosomes. Electron micrograph of the rough endoplasmic reticulum (rER) and polyribosome complexes

Question 415

Identify structure

Answer 415

The large spiral cytoplasmic assemblies (arrows) are chains of ribosomes that form polyribosomes that are actively engaged in translation of the mRNA molecule.

Question 416

The first 15 to 60 amino acids on the
amino-terminus forms a ________

Answer 416

signal sequence (signal peptide SP)

Question 417

The signal peptide interacts with a _________

Answer 417

signal recognition particle (SRP)

Question 418

Explain the cascade of protoein synthesis for export snd sorting sequence

Answer 418

The first 15 to 60 amino acids on the
amino-terminus forms a signal sequence
(signal peptide SP)
* The signal peptide interacts with a signal
recognition particle (SRP)
* The complex SRP–polyribosome arrests
polypeptide synthesis and moves to the
rER membrane
* SRP binds to a docking protein of rER
* Now, synthesis resumes with peptide
going into lumen of rER.
* Dissociation of the SRP–docking protein
complex from the ribosome and rER
membrane occurs
* Protein synthesis continues towards the
lumen of the rER

Question 419

Identify structureS

Answer 419

Electron micrograph of the rER and polyribosome complexes. We can see pores, nucleous, nuclear membrane, cisternae of rER

Question 420

Mention some modification that occur by enzymes in the proteins synthesized into the lumen of the rER and why?

Answer 420

-Glycosylation
– Disulfide-bond
– Hydrogen-bond
– Protein folding is achieved with the help of proteins called chaperones.

they need more processing

Question 421

Why is the rER a quality checkpoint?

Answer 421

Properly modified proteins are concentrated in a lumen of the rER to be delivered to the Golgi. Proteins secreted by the constitutive pathway, are delivered to the Golgi apparatus within minutes

Question 422

Explain the alpha-1 antitrypsin deficiency

Answer 422

a communication problem between rER and Golgi Apparatus. characterized by inability of rER to export a mutated protein to
Golgi apparatus.
In alpha1- antitrypsin (A1AT [gets accumulated in the rER without doing its function]) deficiency, one single amino acid substitution causes
accumulation of defective A1AT within the rER cisterna of liver hepatocytes. The
result is impaired liver function. Also the lack of enzyme contributes to cause
emphysema in the lungs. (basically damages the alveolos of lung)

Question 423

Identify structure and explain

Answer 423

Electron micrograph of a hepatocyte from the liver of a child with α1-antitrypsin deficiency. The arrow shows the accumulation of
α1-antitrypsin within the rER causing impaired function

Question 424

Identify structure and what does it relate to

Answer 424

Emphysema; alpha1- antitrypsin (A1AT) deficiency

Question 425

How to proteins move from rE to the golgi?

Answer 425

in small transport vesicles

Question 426

Identify structure

Answer 426

Electromyograph of hepatocyte showing rER and Golgi apparatus. also transport vesicles full of proteins to be transported to the golgi

Question 427

Who’s the FedEx of the cell?

Answer 427

the golgi apparatus

Question 428

Mention the two classes pf vesicles involved in the transport of proteins

Answer 428

COP I nad COP II

Question 429

Explain COP I

Answer 429

mediates transport vesicles originating in the Golgi back to rER, as well as retrograde transport between Golgi cisternae. This
retrograde transport returns proteins mistakenly transferred to the Golgi

Question 430

Explain COP II

Answer 430

coats the transport vesicles responsible for the anterograde transport that mediates transport of proteins from rER to Golgi.

Question 431

Identify

Answer 431

Camillo Golgi’s drawings of cells in spinal ganglia (1898).

Question 432

What was the “internal reticular apparatus?

Answer 432

In 1897 Camillo Golgi studying the nervous
system with his “black reaction” (silver
impregnation) described an intracellular
structure called like that

Question 433

Explain the staining of the golgi by camilo

Answer 433

Impregnated with silver or osmium (osmiophilic) appears as juxtanuclear structure

Question 434

How does the golgi look in LM?

Answer 434

appeared unstained with most histological stains including hematoxylin or eosin (H&E). The term “negative Golgi” was used for that unstained region of the cytoplasm

Question 435

How does the golgi look in LM?

Answer 435

parallel stacks of flattened closely apposed, membrane-bound saccules or cisternae, and associated vesicles

Question 436

Where is the golgi present?

Answer 436

present in all cells and it is well developed in secretory cells

Question 437

Identify

Answer 437

PLASMA CELLS (secretory cells that produce
immunoglobulins) – “Negative Golgi”

Question 438

Identify

Answer 438

Negative golgi, lack of staining in the apical region

Question 439

Identify strcutures

Answer 439

Electron micrograph of Golgi Apparatus; cis-golgi network, rER; vesicles

Question 440

Describe the Cis-golgi network forming face and its coposition

Answer 440

Convex cisterna, osmiophilic, closest to rER. Mannose phosphorylation (M-6-P) occurs here (for proteins that go to the lysosomes). It stains in EM.

Question 441

Describe the intermediate compartment of the golgi and its composition

Answer 441

Nicotinamide adenine dinucleotide phosphatase (NADPase)
* N-acetyl glucosamine transferase (agt)

Question 442

Describe the trans-golgi network maturing face and its coposition

Answer 442

Concave cisterna, stains for sialyl transferase and galactosyl transferase
* Thiamine pyrophosphatase activity.
* Site of condensing vacuoles and vesicles

Question 443

Identify

Answer 443

The Golgi apparatus in a cultured fibroblast stained with a fluorescent antibody that recognizes a Golgi resident protein.

Question 444

Mention the functions of the golgi

Answer 444

1. Posttranslational modification, sorting
   and packaging of secretory products
   synthesized in rER.
2. Synthesis of some carbohydrate
   components of complex glyco-proteins
   associated with glycosyl transferase.
   GAGs, glycoproteins, glycolipids,
   proteoglycans.
3. Trimming of oligosaccharides in
   glycolipids and glycoproteins
4. Transport and modification of
   membrane proteins and glycolcalyx
5. Mannose-6-phosphate is added to
   proteins destined for lysosomes (phosphorilation of proteins)

Question 445

Identify structures and regions

Answer 445

Condensing vacuole in formation for cytoplasm, secretory cell. This electron micrograph shows the extensive Golgi apparatus in a cell of the pancreas. The
flattened membrane sacs of the Golgi apparatus are arranged in layers. The cis-Golgi network (CGN) is represented by the flattened vesicles on the outer convex surface, whereas the flattened vesicles of the inner convex region constitute the trans-Golgi network (TGN). Budding off the TGN are several
condensing vesicles (vacuoles) (1). These vesicles are released (2) and eventually become secretory
vesicles (granules)

Question 446

What are sorting signals in the golgi?

Answer 446

attached to proteins, determine intracellular location/destine of the protein. Sorting signals can be linear polypeptide arrays or carbohydrate molecules

Question 447

Mention the four major pathways of protein secretion from the Golgi disperse proteins to various cell destinations

Answer 447

apical plasma membrane (mas sencillo)
basolateral plasma membrane
endosomes or lysosomes
apical cytoplasm

Question 448

Explain the apical plasma membrane pathway

Answer 448

Many extracellular proteins and membrane
proteins are delivered to this site.
The constitutive pathway most likely
uses non-clathrin-coated vesicles

Question 449

Explain the basolateral plasma membrane pathway

Answer 449

Proteins with specific sorting signal attached to them by the TGN. This constitutive pathway uses vesicles coated with unique proteins that bind to epithelium-specific adaptor proteins. The transported membrane proteins are continuously incorporated into the basolateral
membranes. Present in most polarized epithelial cells.

Question 450

Explain the endosome or lysosome pathway

Answer 450

The majority of proteins destined to
organelles have specific signal
sequences. Enzymes destined to
lysosomes use Mannose-6-phosphate (M-6-P) markers and are delivered to early or late
endosomes. occurs in the cis with specific signal

Question 451

Explain the apical cytoplasm pathway

Answer 451

Proteins stored in large secretory vesicles undergo a maturation process and are retained within the vesicle. Eventually fuse
with plasma membrane to release secretory product by exocytosis. Characteristic of secretory cells in exocrine glands. they have to live in the cytoplasm for a while until the signal arrived for them to be secreted.

Question 452

identify the pathways

Answer 452

apical plasma membrane (mas sencillo)
basolateral plasma membrane
endosomes or lysosomes
apical cytoplasm

Question 453

Identify the structure

Answer 453

Light micrograph of pancreatic acinar cells (H&E). Apical region showing secretory granules

Question 454

Identify the structure

Answer 454

Electron micrograph of pancreatic acinar cells showing mature secretory granules (S)

Question 455

Identify the structure

Answer 455

Transfer Electron Microscopy (TEM) shows a system of cytoplasmic
membrane-enclosed compartments associated with all endocytotic
pathways. AN early endosome.

Question 456

What is the stable compartment model?

Answer 456

Describes early and late endosomes as stable cellular organelles connected by vesicular transport with the cell exterior and with the
Golgi apparatus. Coated vesicles fuse only with the early endosomes because they have specific surface receptors

Question 457

What is the maturation model?

Answer 457

Early endosomes are formed de novo from endocytotic vesicles, their
composition changes as some components are recycled between the
cell surface and the Golgi. The maturation leads to the formation of
late endosomes and then to lysosomes

Question 458

What is the major function of the early endosomes?

Answer 458

to sort and recycle proteins internalized by endocytotic pathways

Question 459

How is the pH comparison in early endosome to lysosome, why?

Answer 459

in early endosome is less acidic, more basic, in late endosome it turn more acidic and in lysosome is acidic in order to degrade . Each transport add a proton H+ to make the environment more acidic for degradation

Question 460

What are lysosomes

Answer 460

Membrane-bound organelles, containing
50 or more hydrolytic enzymes. They are
responsible for the degradation of
macromolecules derived from
endocytotic pathways and the cell itself

Question 461

Where are lysosomes found?

Answer 461

Present in all cells. Abundant cells of
inflammatory pathways (macrophages
and neutrophils)

Question 462

Lysososme function

Answer 462

sites of intracellular digestion

Question 463

What is endocytosis and autophagy?

Answer 463

-Endocytosis: Macromolecules
brought into the cell (cell “eating”)

– Autophagy: Turnover of cellular
components (cell “eating itself”)

Question 464

How are lysosomes stained?

Answer 464

Acid phosphatase staining:
Histochemical method used to identify
lysosomes. However eaarly endosome doesnt stain here.

Question 465

Identify staining and structure

Answer 465

Electron micrograph of phosphatase
acid reaction staining in lysosome.

Question 466

Identify

Answer 466

lysosomes, mitochondria; primary lysososme since it hasnt digested what its going to degrade.

Question 467

Where is M-6-P present?

Answer 467

In early and late endosomes, lysosomes and golgi

Question 468

TO which enzyme does several enzymes attach in the lysososmal emembrane

Answer 468

M-6-P

Question 469

Describe the membrane of the lysosomes?

Answer 469

resistant to the hydrolytic digestion occurring in their lumen. *Unusual phospholipid
structure: Cholesterol + lysobisphosphatidic acid

Question 470

Mention the structural lysosomal membrane proteins

Answer 470

-Lysosome-associated
membrane proteins
(LAMPs)
* Lysosomal membrane
glycoproteins (LGPs)
* lysosomal integral
membrane proteins
(LIMPs)
* Proton H+ pumps,
transport proteins.

Question 471

Explain the constitutive secretory pathway

Answer 471

Proteins secreted to the cell > surface > endocytosed > early endosomes > late endosomes > lysosomes.

Question 472

Explain the The Golgi-derived coated vesicle
secretory pathway

Answer 472

Proteins exit the Golgi in clathrin-coated vesicles > late endosomes > lysosomes

Question 473

How do lysosomes digest small extracellular particles?

Answer 473

are internalized by both receptor mediated endocytosis and pinocytosis (red arrows) -> endosome -> late endosome -> lysosome

Question 474

How do lysosomes digest large extracellular particles?

Answer 474

such as bacteria and cellular debris are
delivered via the phagocytotic pathway (blue arrows) -> phagosome -> late endosome -> lysosome

Question 475

What is autophagy?

Answer 475

when the cell uses lysosomes to digest itself by creating a membrane from sER

Question 476

What are the types of autophagy?

Answer 476

-macroautophagy
-microautiphagy
-chaperone-mediated autophagy

Question 477

What is macroautophagy?

Answer 477

a portion of the cytoplasm or an entire organelle is surrounded by an
intracellular membrane of the endoplasmic reticulum to form a double-membraned
autophagosome vacuole. After fusion with a lysosome they are degraded

Question 478

What is microautophagy?

Answer 478

cytoplasmic proteins are internalized into lysosomes by invagination of the lysosomal membrane

Question 479

What is chaperone-mediated autophagy?

Answer 479

to lysosomes is the most selective process for degradation of specific cytoplasmic proteins. Participation of proteins called chaperones. The chaperone protein (hsc73) binds to the protein and transports it into the lysosomal lumen, and it is degraded.

Question 480

What is this structure?

Answer 480

Autophagosomes

Question 481

What is this structure?

Answer 481

Undigested residues from both autophagy and heterophagy form Residual bodies. Also called lipofuscin pigment when identified in neurons with light microscopy techniques

Question 482

Can cells destroy proteins without lysosomes? yes? no? how?

Answer 482

Yes, via proteosomes which destroy abnormal proteins misfolded, short-lived regulatory proteins, transcriptional factors.

Question 483

Are proteosomes ATP dependent or independent?

Answer 483

ATP dependent

Question 484

Which aggregations take part in proteosomes?

Answer 484

Ubiquitin 4 molecules

Question 485

What happens if degradation with proteosomes does take place? or if there is accelerated degradation?

Answer 485

accumulation of tau protein (alzheimers); human papilloma virus

Question 486

What is the fucntion of mitochondria?

Answer 486

Provide energy for biosynthetic and motor activities of cells, mir=tochondrial DNA encodes 13 enzymes involved in oxidative phosphorilation, 2 rRNAs, 22 transfer (RNAs).

Question 487

What are TIM and TOM complexes?

Answer 487

Chaperone proteins assist in translocation of proteins

Question 488

What is this structure?

Answer 488

Electron micrograph of skeletal muscle, showing abundant mitochondria in the
intermyofibrillar spaces in striated muscle cells

Question 489

What us this structure?

Answer 489

Mitochondria

Question 490

What is this structure?

Answer 490

Fluorescent microscopy of cells were fixed and stained with phalloidin stain
conjugated with fluorescein dye. Phalloidin binds and stabilizes actin filaments,
preventing their depolymerization. Accumulation of actin filaments at the
periphery of the cell just beneath the plasma membrane. These cells were also
stained with two additional dyes: a mitochondria-selective dye (i.e., MitoTracker
Red) that allows the visualization of mitochondria (red) in the middle of the cell
and DAPI stain that reacts with nuclear DNA and exhibits blue fluorescence over
the nucleus

Question 491

What is this structure?

Answer 491

Mitochondria within hair cells of a sensory system in fish. 3-D reconstructions of
sensory hair cell patches with mitochondria labeled with Mito-Tracker in white.
Scale Bar: 5um.

Question 492

describe the outer mitochondrial membrane

Answer 492

Permeable, voltage-dependent anion channels called porins. Posses TOM complexws for importing proteins into the intermembrane space. Also contains Acetyl CoA, phospholipase A2, monoamine oxidase, synthase

Question 493

Describe the inner mitochondrial space

Answer 493

impermeable, has cristae for amplification of furcae area for efficiency of energy generation. Steroid metabolism, wich in phospholipid cardiolipin makes the membrane impermeable of ions.

Question 494

Whta is this structure?

Answer 494

Elementary particles, for oxidative phosphorilation, for ATP generation.

Question 495

Describe intermembrane space

Answer 495

Space between the inner and outer membranes and contains specific enzymes that use ATP. These enzymes include creatine kinase, adenylate kinase, and cytochrome c. The latter is an important factor in initiating apoptosis

Question 496

Describe mitochondrial matrix

Answer 496

Surrounded by the inner mitochondrial membrane and contains the soluble enzymes of the citric acid cycle (Krebs cycle) and the enzymes involved in fatty-acid β-oxidation

Question 497

Describe the matrix granules of mitochondria

Answer 497

Store Ca2+ and other divalent and trivalent cations. Mitochondria can accumulate cations and regulate the concentration of cations in the cell, a role they share with the sER. The matrix also contains mitochondrial DNA, ribosomes, and tRNAs

Question 498

What is this structure?

Answer 498

matrix granules

Question 499

What is this structure and mechanism?

Answer 499

mitochondria dividing by fission

Question 500

Which is the proapoptotic protein?

Answer 500

BCl2 regulates eprmeability adn leads to irreversible release of cytochrome c

Question 501

What is the orthodox configuration and condensed configuration?

Answer 501

1) The orthodox configuration, the cristae are
prominent, and the matrix compartment
occupies a large part of the total mitochondrial
volume. This configuration is observed in
healthy cells.
2) The condensed configuration is
characterized by unfolded cristae that are not
easily recognized and the intermembrane space
increases to as much as 50% of the total volume
of the organelle. These changes expose
cytochrome c and facilitate its release from the
mitochondria during apoptosis.

Question 502

What is this strcuture?

Answer 502

orthodox config and condensed config

Question 503

emention some effects of mitochondrial defects

Answer 503

Metabolically active tissues that use large amounts of ATP, such as muscle
cells and neurons, are the most commonly affected.
Myoclonic epilepsy with ragged red fibers (MERRF)
* Is characterized by muscle weakness, seizures, and cardiac and
respiratory failure. Microscopic examination of muscle tissue from
affected patients shows aggregates of abnormal mitochondria.
* MERRF is caused by mutation of the mitochondrial DNA gene encoding
tRNA for lysine (to add a lysine amino acid). This defect affects the
electron-transport chain of respiratory enzymes affecting ATP production

Question 504

What are peroxisomes?

Answer 504

Small membrane bound organelles, containing more than 40 oxidative enzymes. Lack acid phosphatase (found in lysosome). H2O2 (hydrogen peroxide) is a product of oxidation reactions and it is a toxic substance. Excess hydrogen peroxide is destroyed by the enzyme catalase.

Question 505

Where are peroxisomes abundant?

Answer 505

Abundant in liver and kidney, the number of peroxisomes increases in
response to diet, drugs, and hormonal stimulation. In liver, peroxisomes
are responsible for detoxification of ingested alcohol

Question 506

What does the nucleoid of the peroxisome have?

Answer 506

crystalloid of urate oxidase

Question 507

What is this structure?

Answer 507

Peroxisomes; crystalloid of urate oxidase

Question 508

WHat is this structure?

Answer 508

Glycogen (alpha particles) in liver

Question 509

What si this structure?

Answer 509

Electron micrograph of skeletal muscle showing mitochondria and abundant amount of glycogen particles (beta)

Question 510

What is this structure?

Answer 510

lipid droplets, energy store abundant in sER

Question 511

What is this structure?

Answer 511

Melanin pigment

Question 512

What is this structure?

Answer 512

Lipofuscin pigment, brownish gold; wear and tear, cellular aging.

Question 513

What is lipofuscin?

Answer 513

Lipofuscin is a aggregation of oxidized lipids, phospholipids, metals, and organic molecules that accumulate within the cells as a result of oxidative degradation of mitochondria and lysosomal digestion.

Question 514

What is this structure?

Answer 514

Electron micrograph of aneuron showing a group of neurofilaments and residual
bodies (lipofuscin pigment in light microscopy

Question 515

What is this strcture?

Answer 515

microvilli, brush border of small intestine

Question 516

What is this structure?

Answer 516

Epididymis with stereocilia

Question 517

What is this structure?

Answer 517

Tracheal epithelium with cilia

Question 518

What is this structure?

Answer 518

cilia

Question 519

What is this structure?

Answer 519

microvilli of intestinal “finger-like structures”

Question 520

What is this structure?

Answer 520

stereocilia

Question 521

What is this structure?

Answer 521

cilia

Question 522

What is the core of microvilli? and what is the border?

Answer 522

bundle of parallel microfilaments, striated border

Question 523

What is the main function of microvilli?

Answer 523

absorption, increase surface area for better absorption.

Question 524

What is this structure?

Answer 524

periodic acid stain, stains carbohydrates due to glycocalyx in microvilli

Question 525

What is this structure?

Answer 525

microvilli

Question 526

What is this structure and its components?

Answer 526

microvilli on intestinal cell showing central bundle of actin-containing microfilaments

Question 527

What is this structure?

Answer 527

microvilli with core bundle of actin filaments and actin filaments as a loose meshwork in cytoplasm below microvilli

Question 528

What is this structure?

Answer 528

Bundle of actin filaments in cross section in microvilli

Question 529

Mention the proteins in the molecular structure of microvilli

Answer 529

cross-linked: fimbrin, fascin, espin
attaches to plasma membrane: myosin I
anchored at tip: villin
terminal web: myosin II, spectrin, alpha-actinin

Question 530

Where can we found stereocilia?

Answer 530

Found in male reproductive tract in the epididymis and vas deferens where they are involved in and regulate absorption of fluids from semen and in hair cells in the inner ear for perception of sound

Question 531

What is the stereocilia structure?

Answer 531

Have actin bundle at core
crosslink proteins: espin, fimbrin and fascin can be present
villin is absent
attachement to memebrane: ezrin instead of myosin I
alpha-actinin can be cross-linked to other stem regions.

Question 532

What does stereocilia do in the inner ear?

Answer 532

act as mechano-sensors of fluid movement in the ear which is perceived as different sounds, bending of hair cell causes calcium channels to open and depolarize the cel and stimulate adjacent auditory nerve.

Question 533

What is this structure?

Answer 533

scanning EM of stereocilia in the inner ear. (b) Espin labeled by fluorescent
green marker can be seen adding at the tip of the stereocilia. (c) diagram showing the
molecular mechanism for the addition of new actin molecules and crosslinking
moleculesat the tip of the stereocilia

Question 534

What is threadmillinf in stereocilia?

Answer 534

constant renewal of actin and crosslink proteins at the + tip, repair mechanism

Question 535

What is usher syndrome?

Answer 535

Usher syndrome is characterized by hearing loss, visual impairment due to retinitis pigmentosa (RP), and in some cases, vestibular dysfunction. Usher syndrome is the most common cause of deaf-blindness and an important etiology underlying autosomal recessive deafness.
Proteins encoded by Usher genes have been found to be particularly abundant in the stereocilia and the synaptic regions of hair cells and guide the cohesion and development of the hair bundles. Mutations in these proteins typically lead to deafness thus showing the importance of the stereocilia and the maintenance of their structure,

Question 536

Where can we find cilia and how they differ from microvilli and stereocilia?

Answer 536

on the apical surface of many epithelial cells. They differ from both microvilli and stereocilia in having a core structure composed of an arrangement of microtubules and by their ability to move (in some types)

Question 537

Mention the 3 types of cilia

Answer 537

-Motile cilia which can move
-primary cilia (monocilia, are imotile but have sensory function
-nodal cilia (a type of monocilium that can move and its important for embryological development on te ventral node

Question 538

Where can we find motile cilia?

Answer 538

commonly found on cells which are involved in moving material along their apical surfaces such as in the respiratory system (mucus) and oviduct (the oocyte), or in the form of flagella for moving the entire cell (sperm

Question 539

What is this structure?

Answer 539

motile citia

Question 540

What is this structure?

Answer 540

motile cilia in the trachea for movement of mucus.

Question 541

What is this structure?

Answer 541

motile cilia in the oviduct (thicker)

Question 542

How is the moelcular structure of cilia called?

Answer 542

axoneme

Question 543

How is the axoneme characterized?

Answer 543

9+2 arrangement of microtubules

Question 544

by what are the 9 doublets connectedto teh 2 central microtubules?

Answer 544

radial spokes

Question 545

Protein that connect the microtubule doublets

Answer 545

nexin-linking protein

Question 546

How is the arrangement of the basal body in motile cilia?

Answer 546

9 triplet strcuture

Question 547

What dies dyenin do in motile cilia?

Answer 547

the bending of cilia.

Question 548

How can the doublets in motile cilia be divided?

Answer 548

a-subfier (13 protofilamets) and b-subfiber (10-11 protofilaments)

Question 549

What is this structure?

Answer 549

basal bodies of motile cilia

Question 550

Identify structures

Answer 550

Nexin link, radial spoke, a-subfiber, b-subfiber, dyenin arms

Question 551

What is the effcetive stroke, the recovery stroke and metachronal rythm in motile cilia?

Answer 551

Requires ATP hydrolysis. This is the forward effective stroke.
*
The elastic recoil of the nexin and radial arm proteins then returns the cilium to original position (recovery stroke)
*
The adjacent cilia beat in a coordinated metachronal rhythm which is a wave of movement to rpopel fluid like trapped bacteria along the epithelium

Question 552

how do basal bodies arise?

Answer 552

either by duplication of existing centrioles (centriolar pathway) or by a denovo pathway (acentriolar pathway)

Question 553

Protein that anchors basal body to cytolasm

Answer 553

rootletin

Question 554

identify

Answer 554

basal bodies, axoneme, basal foot, striated rootlet, transitional zone

Question 555

identify

Answer 555

basal bodies

Question 556

What is the pattern of primary cilia (monocilia)

Answer 556

have a 9 + 0 pattern of microtubule doublets, no dyenin arms; non-motile

Question 557

Where can we find monocilia?

Answer 557

Are present on most cells in epithelial, connective, muscle and nervous tissues

Question 558

identify

Answer 558

monocilia (primary cilia)

Question 559

What are some functions of primary cilia?

Answer 559

monitor fluid flow through the kidney tubules, biliary tubules, brain ventricles, and auditory system.
*
There presence has been found to be critical for function in the organs in which they are present

Question 560

What dies polycystine-1,2 do?

Answer 560

initiate signaling cascades within the cell by movement of fluid.

Question 561

Whst is the nodal cilia and what are they important for?

Answer 561

unique form of monocilium found on cells in the region of the ventral node in the developing embryo and are thought to be important for determining the left-right patterning of the embryo

Question 562

What is the pattern of nodal cilia?

Answer 562

+ 0 pattern of microtubule doublets like primary cilia but are motile since they have dynein arms. This distinguishes them from primary cilia (monocilia), only asingle ciliu present

Question 563

Identify

Answer 563

This figure shows a scanning EM (A) of nodal cilia on the surface of nodal cells in the ventral node

Question 564

identify

Answer 564

Nodal cilia

Question 565

Why is the rotation “like a propeller” of nodal cilia important

Answer 565

In the region of the primitive node in the embryo they rotate in a clock-wise manner and generate a leftward or “nodal” fluid flow which is detected by sensory receptors on the left side of the embryo and helps to establish left-right symmetry of the organs.

Question 566

What can happen if there are defects in the proteins of nodal cilia?

Answer 566

cause “situs inversus” in which the heart and other organs appear on the wrong side of the body in approximately 50% of the patients with the defects

Question 567

What proteins acts as transport motor up and motor down in Intrafagellar transport in cilia (IFT)

Answer 567

kinesin II; dyenin

Question 568

Mention the function of IFT?

Answer 568

provides precursor molecules to tip of cilia and removes old molecules

Question 569

what are some mutations in IFT?

Answer 569

Mutations in genes encoding the proteins in the IFT-A and IFT-B complexes result in loss of cilia or result in ciliary dysfunctions.
For instance, mutations in the genes for kinesin II the main anterograde transport protein in cilia (KIF3A/KIF3B/KAP3 trimeric complex) can result in either very short or absent cilia; resulting in ciliary disfunction related to a number of clinical conditions called ciliopathies.

Question 570

What are some ciliopathies (primary cilia dyskinesia or immotile cilia syndrome?

Answer 570

*
Autosomal dominant polycystic kidney disease (ADPKD) resulting in cysts in kidney leading to renal failure, and can also cause cysts in pancreas and liver
*
Chronic infections of the lungs & upper airways due to inability of the respiratory cells to move mucus along their surface. For example, Kartegener’s syndrome.
*
Situs Inversus with inversion of the side on which organs occur. As noted above this may be primarily related to defects in the nodal cilia
*
Infertility in males due to immotile sperm
*
An increased rate of ectopic pregnancy in affected females that cannot properly move the oocyte along the oviduct
*
Hydrocephalus internus (accumulation of fluid in the brain ventricles) may occur in patients due to defective motile cilia on the ependymal cells lining the cerebrospinal fluid-filled spaces in the brain

Question 571

Explain parthologies involving primary cilia ADPKD

Answer 571

Autosomal dominant polycystic kidney disease (ADPKD) is the major type of polycystic kidney disease (PKD). It is characterized by formation of multiple fluid-filled cysts which destroy the renal cortex leading to more than half of patients progressing to renal failure.
*
ADPKD is associated with mutations in the Pkd1 and Pkd2 genes which encode for the proteins polycystin-1 (PC1) and polycystin-2 (PC2) in the membrane of the primary cilium. These proteins normally interact to form an ion channel complex that is necessary for signaling pathways and for the mechanosensory function of the primary cilium. The exact mechanism by which the mutations lead to formation of the cysts, however, is still unclear.
*
Individuals with ADPKD often exhibit other pathologies not associated with the kidney that are attributed to ciliary abnormalities. These include cysts in the pancreas and liver that are accompanied by an enlargement and dilation of the biliary tree system

Question 572

What is kartager’s syndrome?

Answer 572

Congenital abnormality typically involving absence of the motor protein dynein from motile cilia and nodal cilia
Kartagener’s Syndrome can result in defects in ability of respiratory epithelial cells to transport mucus (mucociliary transport) in the tracheo-bronchial tree. This results in chronic respiratory disorders (bronchitis and sinusitis), otitis media (inflammation of middle ear), persistent cough, and asthma

Question 573

Identify pathology

Answer 573

Lack of dyenin arms, kartagener’s syndrome