Cell and Tissue Structure 3

Question 1

what is the cytoskeleton?

what does the cytoskeleton mean regarding how rigid the cell is?

Answer 1

def: the network of protein structures that maintains the physical integrity of the cell and allow for transport of organelles and vesicles throughout cell.

rigidity - allows to be flexible whilst maintaining mech. support

Question 2

which protein fibres is cytoskeleton made from?

Answer 2

1. microfilaments (made from actin)
2. intermediate filaments
3. microtubules

Question 4

describe the structure and function (3) of microfilaments

Answer 4

structure: made of helical structures of actin

function: - mechanical support

• allows for movement of organelles along the actin filaments
• in muscles, allow contraction together with myosin

-

Question 5

give an example of disease arising from actin not being produced correctly

Answer 5

‘floppy babies’ - babies luck muscle strength

Question 6

what are intermediate filaments used for?

Answer 6

function: tensile strength whilst maintain flexibilty

made from: different cell types are made from different intermediate filaments:

• e.g. skin’s intermediate filament = keratin.

Question 7

what is a disease associated with keratin?

Answer 7

epidermolysis bulbosa - easy blistering of skin (skin cells dont have support structure of intermediate filaments)

Question 8

describe structure and function (4) of microtubules :)

Answer 8

structure:

- large tubular structure

• hollow
• made from tubulin

Functions:

- prevent the cells from being compressed

- scaffolding on which organelles and vesicles move

• form the framework of the mitotic spindle required for cell division

- act as flagella or cilia

Question 9

why can make phospholipd bilayer structure complex?

Answer 9

due to the various proteins that attach either to the membrane or span all / part of the membrane

Question 10

what are the functions of the plasma membrane?

Answer 10

1. protection
2. communcation
3. permeability
4. identification
5. cell adhesion
6. anchor cytoskeleton
7. interaction with ECM

Question 11

what is the basal membrane / basal lamina?

how many layers / what layers name?

what is the basal membrane / basal lamina made from?

Answer 11

a layer of extracellular matrix secreted by the epithelial cells, on which the epithelium sits.

separated into two layers: (collagen lies in different direction for them)

1. Lucida

2. Densa

made from type IV Collagen, Laminin and a Heparin Sulfate

Question 12

what is the function of the basal lamina / basement membrane? (4)

Answer 12

1. provides structural support for epithelia to stay on it. therefore give tissue and organ their shape
2. relays functional messages through epithelia, to cells within organ
3. as a messenger for growth factors
4. physical barrier
5. provides anchorage to the epithelia

REALLY IMPORTANT IN GIVING ORGANS AND TISSUES THEIR BASIC STRUCTURE AND INTENSITY

Question 14

describe two diseases of the basal membrane

Answer 14

1. epidermolysis bulbosa - mutations in laminin -> easily peals off and so does the skin above it
2. cancer - (usually cant cross into organs because the basal membrane divides the organ from the rest of the body. but epithelial - mesenychymal transition - where does cross and becomes metastatic)

Question 15

what connects cells ? (some but not all)

Answer 15

inter-cellular junctions

Question 16

name the types of inter-cellular junctions

Answer 16

1. tight junction
2. adherens junction
3. desmosome
4. gap junction
5. hemidesmosomes

Question 17

describe the function of tight junctions

where are tight junctions usually found?

Answer 17

1. hold cells together
2. provide a physical barrier between outer and inner side of cells -> prevent bacteria, ion and molecules from crossing

found: on luminal side side of cells

Question 18

which diseases result in disruption of tight junctions?

Answer 18

AD, Parkinsons, MS, Stroke

Question 19

describe the function of adheren junctions

where are adheren junctions usually found?

what is their core made from?

explain how connect adheren junction conncet from one cell to another

Answer 19

function: hold tightly one cell to next. BUT: linked to actin cytoskeleton of adjacent cells. crosses membrane of both cells. also: wound healing

location: epithelia and endothelial cells. located basally than tight junctions

core: cadherin molecules, adhere tightly (w/ calcuium) and bind catenin to cytoplasm of one cell to cytoskeleton of other cell

connection: cadherin (cell 1) -> catenin (intracellular space) -> actin filamet (cell 2)

Question 21

describe the function of desmosomes

where usually found?

Answer 21

function: attach adjacent cells together. BUT: instead of connecting actin filaments, have a plaque that connects to intermediate filaments. strong attachment.

location: tissues that are in high mechanical stress (they reduce stress on the cells). e.g cardiac cells

Question 22

give a disease associated with desmosomes?

Answer 22

1. arrhythomogenic right ventricular cardiomyopathy: (mutation in desmogelin gene) defective desmosomes -> sudden death due to hearts bursting
2. Pemphigus vulgaris - autoimmune disease that attacks desmosomes -> blisters

Question 23

describe function of gap junctions

what are gap junctions made from?

what is bystander effect?

Answer 23

junction: allow movement of substances between cytoplasm of adjecent cells. regulated passage. can make chemical and electric gradients.

made from: protein connexin - 6 connexin molecules one side connect to 6 connexin molecules on other side.

bystander effect: one cell signals apoptosis in adjacent cell without generating own signals themselves

Question 24

what are pseudopodia?

how occur?

Answer 24

function: temporary cytoplasm-filled projection of cell membrane for movement and ingestion

movement: rearrangement of cytoskeleton (extesnion of actin, contraction of myosin)

Question 25

what are lamellipodia and filopodia?

Answer 25

lamellipodia: (blade foot) flat broad protrusions that allow a cell to move forward and make contact with other cells and env

filopodia: long thin projections that extend several micrometers ahead of cells.

= both for sensing other cells and nearby env.

both require ATP to drive poylmerization of actin filaments

Question 27

where microvilli found?

function?

structure?

Answer 27

function: increase SA for absorbtion and secretion - by c. 600x.

location: cell surface of absorbative and secretory cells like kidney / intestinal cells

structure: an extension of cell membrane, maintained by actin filaments

Question 28

what are microvilli covered with?

Answer 28

glycocalyx - glycoprotein. allows enzymes to stick to surface of microvilli - increases SA for digestive enzymes

Question 29

microvilli in disease?

Answer 29

infections: e.g. celiac disease - disrupt the structure of epithelial layer -> diarhhoea and fever

toxins: can destroy microvilli by targeting gap junctions

congenital lack of microvilli: microvillus atrophy

Question 30

what types of cilia exist?

Answer 30

function: slender protuberances that project from cell body.

structure: motile or non-motile:

non-motile: sensory surfaces (like ears). microtubules on side (no actin - no movement)

motile: trachea (move mucus). two actin and myosin tubules in centre

Question 31

disease associated with cilia?

Answer 31

Bardet-Biedl syndrome: defective cilia. affact numerous critical development pathways like obesity / lack of sexual development