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Y1 - Histo/Embryo - Daniels > L1 - Intro to Cell, Nucleus, &Cytoplasm > Flashcards

L1 - Intro to Cell, Nucleus, &Cytoplasm Flashcards

K&T pg 63-9,74-84

1
Q

plasma membrane: purpose

A

determines the structural and functional boundaries of a cell

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2
Q

cytomembranes: definition

A

intracellular membranes that separate diverse cellular processes into compartments called organelles

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3
Q

organelles: definition

A

intracellular compartments that house specific cellular processes, encased by cytomembranes

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4
Q

list the membrane-bound organelles?

A

L, M, N, P Lysosomes, mitochondria, nucleus, and peroxisomes

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5
Q

list cellular components that are NOT membrane-bound

A

glycogen and lipids (glycogen and lipids lack a membrane)

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6
Q

what are “cytoplasmic inclusions”? name 2 examples

A

def: diverse intracellular, non-living substances that are not able to carry out metabolic activity and do NOT have membranes. eg: glycogen granules of liver or muscle cells, or lipid droplets in fat cells, pigment granules in certain skill/hair cells, or water-containing vacuoles

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7
Q

2 major components of the plasma membrane

A

lipids and proteins

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8
Q

function of phospholipid bilayer?

A

fundamental structure of membrane, forming bilayer barrier between 2 aqueous compartments (intracellular/extracellular)

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9
Q

location and function of proteins in phopholipid bilater

A

found embedded w/in phospholipid bilayer. these carry out specific functions of the PM such as cell-cell communication, recognition, and selective transport of molecules

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10
Q

3 general functions of membrane lipids

A

1) amphipathic property to allow separation of internal/external environment
2) allows aggregation or dispersement of some intramembranous proteins
3) lipids help with cell signaling

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11
Q

the amphipathic property of the PM enables…

A

enables cells and organelles to establish internal setting separated from external environment

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12
Q

describe the structure of “polar lipids” of cell plasma membranes?

A

hydrophobic portion that self-associates, and hydrophilic portion that interacts with water-containing molecules.

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13
Q

examples of 2 lipids that participate in cell signaling

A

phosphatidylinositol: phosphorylated forms of phosphatidylinositol (PI) are called phosphoinositides and play important roles in lipid signaling, cell signaling, and membrane trafficking.

diacylglycerol (DAG): a prolific second messenger that activates proteins involved in a variety of signaling cascades

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14
Q

four major phospholipids of plasma membranes, and what % of membrane lipids are these 4 combined?

A
  • phosphatidylcholine
  • phosphatidylethanolamine
  • phosphatidylserine
  • sphingomyelin

(again, that’s phosphatidyl-CHOLINE, -ETHANOLAMINE, -SERINE, and sphingomyelin)

These 4 lipids make up > 50% of total lipid in most membranes

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15
Q

name the 2 components of PMs of animal cells (other than phospholipids)

A
  1. glycolipids
  2. cholesterol
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16
Q

glycolipids: definition, location, structure

A
  1. minor membrane component of animal cell PMs
  2. found in outer leaflet
  3. contains carbohydrate moietites exposed on cell surface, which are the green hexagons outside of membrane in picture attached
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17
Q

cholesterol: definition, location, structure

A
  1. major membrane constituent of animal cell PMs; serves to modulate membrane fluidity by restricting movement of phospholipid FA chains at high temps
  2. inserted into phospholipid bilayer; present in nearly same amounts as phospholipids
  3. rigid carbon-ring structure in phospholipid bilayer
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18
Q

2 key points about structure and consistency of phospholipid bilayer

A
  1. structure of phospholipids (hydrophobic FA chain- interior of bilayer) allows it to serve as barrier between 2 aqueous compartments – keeps PMs impermeable to water-soluble molecues
  2. phospholipid bilayer is a viscous fluid (long HC chains of the FAs are loosely packed interiorly so PLs & proteins can diffuse laterally to perform membrane functions)
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19
Q

rough estimate of composition of plasma membranes

A

50% lipids

50% proteins

(5-10% of membrane mass from carb component of glycolipids and glycoproteins)

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20
Q

what coats the surface of plasma membrane?

A

glycocalyx: (pericellular matrix) the glycoprotein and glycolipid covering that surrounds cell membranes of some bacteria, epithelia, and other cells

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21
Q

how does the glycocalyx act as an “identifier” in the body?

A

it acts as an identifier in that it helps the body distinguish its own healthy cells from those of transplanted tissues, diseased cells, or infading organisms. Tthe glycocalyx contains cell-adhesion molecules that allow cells to adhere to & guide movement of cells during embryonic development

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22
Q

describe the fluid mosaic model

A
  • membranes are 2D fluids with proteins inserted into lipid bilayer
  • proteins and lipids can diffuse laterally through plane of the fluid membrane, but it is hard for proteins and PLs to switch from inner and outer leaflets of membranes
  • NOT ALL proteins can diffuse freely – mobility is limited by association with cytoskeleton
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23
Q

what causes the polarized nature of epithelial cells?

A

restrictions in mobility of membrane proteins

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24
Q

what are the two distinct domains of the membrane? how do they differ

A
  • apical: the layer of plasma membrane on the side toward the lumen of the epithelial cells in a body tube or cavity, separated from the basolateral membrane by the zonula occludens.
  • basolateral: the layer of plasma membrane of epithelial cells that is adjacent to the basement membrane and separated from the apical membrane by the zonula occludens.

these differ in protein composition and function

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25
Q

what is a lipid raft?

A

a region of the plasma membrane enriched in cholesterol and sphingolipids. some lack structural proteins, others are enriched with structural protein that modifieis composition and function of lipid raft;

lipid rafts can participate in cell signaling by concentrating or separating specific membrane-associated proteins in unique lipid domains

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26
Q

what are “caveolin” proteins?

A

components of lipid rafts participating in the traffic of vesicles or caveolae; (caveolae are found in several cell types, particularly in fibroblasts, adipocytes, endothelial cells, type I alveolar cells, epithelial cells, and smooth and striated cells)

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27
Q

name the protein families that can modify the structure and function of lipid rafts

A
  • caveolin protein family
  • flotillins
  • glycosphingolipid-linked proteins
  • Src tyrosine kinases
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28
Q

tight junctions: 2 functions

A

form between adjacent epithelial cells

  1. seal the space between cells
  2. serve as barriers to diffusion of proteins and lipids between the apical and basolateral domains of the PM
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29
Q

what are the 2 major classes of membrane-associated proteins?

A
  1. peripheral proteins
  2. integral membrane proteins
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30
Q

peripheral proteins

A

membrane-associated proteins that are indirectly associated with membranes through protein-protein ionic bonds

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31
Q

what can disrupt the protein-protein ionic bond interactions of peripherap proteins?

A
  • high salt concentration
  • extreme pH
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32
Q

integral membrane proteins

A

portions of these are inserted into lipid bilayer; can only be released via solubilization using detergents

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33
Q

what are “detergents” in the context of PMs?

A

chemical agents containing hydrophobic and hydrophilic groups;

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34
Q

what is the role of the hydrophobic group of the detergent? hydrophilic group?

A

the hydrophobic groups penetrate membrane lipids and bind to membrane-inserted hydrophobic portion of the protein

the hydrophilic groups combine w/ protein, forming aqueous-soluble detergent-protein complexes

35
Q

transmembrane proteins: definition

A

integral proteins that span the lipid bilayer, with segments exposed on both sides of the membrane; typically span through alpha-helical regions;

these can be visualized by freeze-fracture technique

36
Q

inner leaflet composition

A

mostly phosphatidylSERINE, phosphatidylINOSITAL, phosphatidylETHANOLAMINE

37
Q

outer leaflet composition

A

mainly phosphatidylCHOLINE, sphingomyelin, and phosphatidylETHANOLAMINE. Glycolipids are found only in outer leaflet, with carb portion exposed on EC surface

38
Q

explain cholesterol’s relation to inner/outer leaflet?

A

cholesterol is a major membrane component but does not form the membrane itself; rather is modulates membrane fluidity by regulating movement of FA chains of phospholipids in a temp-dependent way

39
Q

freeze-fracture technique: purpose

A

allows visualization of intramembranous proteins w/ an electron microscope

40
Q

freeze-fracture technique: process

A
  1. freeze specimen at liquid nitrogen temp (-196ºC)
  2. “split” with knife under high vacuum along hydrophobic core of membrane
  3. bilayer is split and each half has a surface and a face
  4. replica is produced by evaporating thin layer of heavy metal (e.g. platinum), to produce contrasting shadowing effect
  5. platinum replica is detached from real specimen by floating on water surface, mounted on metal grid, and observed with electron microscope
41
Q

what portion of integral and peripheral membrane proteins are generally glycosylated?

A

the extracellular portion; whereas the intracellular portion is bound to cytoskeletal components

42
Q

what is the “surface” of PM? the “face”?

A

the surface is exposed to the respective space (e.g. extracellular surface is exposed to EC environment); whereas the face is the part previously within the bilayer and is hydrophobic (e.g. faces the EC space)

43
Q

in freeze-fx technique, why and where are “complementary pits” formed?

A

these are formed in the cytoplasmic leaflet because the TM protein/cytosekeltal components may be directly or indirectly attached to tip of protein on cytoplasmic side and will not let go

44
Q

examples of specific transport proteins

A

both carrier proteins and channel proteins help to mediate the selective passage of molecules across the membrane, allowing the cell to control its composition; (b/c most biological molecules cannot figguse thru the phospholipid bilayer)

45
Q

passive diffusion: mechanism and examples of what does this

A
  • molecules can cross the PM down its concetration gradient by dissolving into PL bilayer –> into aq environment at cytosolic/EC side of membrane; this does NOT involve membrane proteins
  • ex: oxygen, CO2, lipid substances
46
Q

transport proteins and channel proteins: function, and transports what?

A
  • facilitates diffusion of most biological molecules that are unable to dissolve in hydrophobic interior of PL bilayer
  • e.g. glucose, charged molecules, and small ions
47
Q

facilitated diffusion: how does it work? what does it require?

A
  • determined by concentration and/or electrical gradients across membranes
  • requires one of the following:
    • carrier protein to bind to specific molecules to be transported
    • channel protein to form open gates thru the membrane
48
Q

carrier proteins transport…

A

sugars, amino acids, and nucleosides

49
Q

channel proteins are…

A

ion channels involved in rapid transport of ions (faster than carrier proteins), are HIGHLY SELECTIVE of molecule size/charge, and are not continuously open

50
Q

ligand-gated channels

A

channel protein that open “gates” in response to binding of a signaling molecule

51
Q

voltage-gated channel

A

channel protein that open in response to changes in electric potential across the membrane

52
Q

endoplasmic reticulum: structure, compartments, part of which system?

A
  • interconnected network of membrane-bound channels w/in cytoplasm, consists of cisternae (flat sacs), tubules, and vesicles
  • divided into luminal/endoplasmic compartment and cytoplasmic/cytosolic compartment
  • part of cytomembrane system, distinct from PM
53
Q

smooth ER: function, key features

A

associated with detoxification reactions to convert harmful lipid-soluble or water-insoluble substances into water-soluble compounds to facilitate discharge by the kidneys

  • lacks ribosomes
  • located near deposits of glycogen and lipids w/in cytoplasm
  • participates in steroidogenesis
54
Q

how are products from luminal compartment of ER transported to Golgi apparatus?

A

via transporting vescile and eventually to exterior of the cell by exocytosis

55
Q

how is lumen of cytomembrane system interconnected?

A

visualize that luminal compartment of secretory cell is continuous with exterior fo the cell; the surrounding space is cytosolic compartment in which soluble proteins, cytoskeletal components, and organelles reside

56
Q

name the 2 leaflets cut during freeze-fx

A
  • exocytoplasmic leaflet faces EC space
  • protoplasmic leaflet faces cytosolic compartment
57
Q

ergastoplasm: what is it, key features

A
  • rough endoplasmic reticulum; a diffuse basophilic cytoplasmic structure
  • ribosomes are attached and synthesize proteins
58
Q

how to proteins exit the RER?

A

via vesicles transported to the cis portion of the Golgi apparatus;

some proteins stay behind in RER to participate in initial steps of protein synthesis (marked w/ KDEL sequence, or Lys-Asp-Glu-Leu, at C-terminal)

59
Q

secretory protein path from RER

A

RER –> Golgi apparatus –> secretory vesicles –> to extracellular space or lumen

(see “signal hypothesis” as to how secretory proteins are directed to the ER)

60
Q

plasma membrane and lysosomal protein path from RER

A

RER –> Golgi apparatus –> retained w/in the cell

61
Q

how are proteins targeted to the nucleus, mitochondria, or peroxisomes created?

A

synthesized on free ribosomes and then released into cytosol

62
Q

how do ribosomes attach to RER?

A

w/ the guidance of amino acid sequence of polypeptide chain being synthesized; ribosomes are directed by signal sequence at the growing ended of a polypeptide chain

63
Q

golgi apparatus: composition

A

cluster of flattened stacks of sacs called “cisternae” stabilized by golgins (coiled-coil proteins); each Golgi stack has:

  1. entry (cis) face adjacent to ER
  2. exit (trans) face continuous with trans-Golgi network (TGN) which points towards plasma membrane or the nucleus

Cisternae of medial-golgi are interposed between the cis and trans golgis.

64
Q

what is “cargo” in the context of ER/golgy?

A

newly synthesized membrane and proteins destined to be stored w/in a cell compartment or secreted to cell exterior;

derived from ER and transport soluble proteins to the cis-Golgi

65
Q

transport vesicles: definition

A

bud off from one cisterna and tether/fuse with the next in presence of golgins; allows transport of cargo material

66
Q

golgins: purpose

A

form appendicular network on cis-Golgi around the rims of the sacs and on trans-Golgi and serve to stablize the golgi structure and to traffick vesicles

67
Q

where do vesicle cargoes continue after trans-Golgi?

A

from trans-Golgi to TGN (tubular-vesicular distribution center of ccargos to the cell surface or another cellular compartment)

68
Q

The Golgi apparatus undergoes a permanent turnover. During which phase does it dissasemble? When does it reassemble?

A

Dissasembles in mitosis/meiosis. (dissasembles when cell divides)

Reassembles in interphase.

69
Q

3 major functions of Golgi apparatus

A
  1. glycosylation
  2. sorting of cargos to several destinations w/in the cell (i.e. marks specific proteins for sorting to lysosomes)
  3. synthesis of sphingomyelin and glycosphingolipids
70
Q

what is glycosylation?

A

modification of carbohydrates attached to glycoproteins & proteoglycans received from the endoplasmic reticulum;

can occur in the golgi apparatus

71
Q

glycosyltransferases

A

enzymes that add specific sugar residues;

more specifically, they catalyze the formation of the glycosidic linkage to form a glycoside. These enzymes utilize ‘activated’ sugar phosphates as glycosyl donors, and catalyze glycosyl group transfer to a nucleophilic group, usually an alcohol.

72
Q

glycosidases

A

enzymes that remove specific sugar residues;

more specifically, they catalyse the hydrolysis of glycosidic linkages, thereby degrading oligosaccharides and glycoconjugates, the structurally most diverse class of biopolymers.

73
Q

Cargos that bud off from the Golgi apparatus can go 2 directions. What are they?

A

Either sorted to the secretory of lysosomal sorting pathway (anterograde traffic - “forward”) or back to the endoplasmic reticulum (retrograde traffic- “backward”)

74
Q

facultative or regulated secretion

A

when certain classes of cargo are stored into secretory granules for later release in response to an extracellular signal.

75
Q

constitutive secretion

A

method by which cargos are secreted continuously w/o a need of a stimulus; this process supplies newly synthesized lipids and proteins to be released outside the cell

(e.g. proteins of the extracellular matrix or immunoglobulins during immune reactions)

76
Q

Where does cargo sorting occur?

A

Along microtubules or actin filaments, with the help of motor proteins.

77
Q

macroautophagy (or autophagy)

A

non-selective macrophagy -

  • non-selective process
  • involves the random sequestration, degradation, and recycling of intracellular components into double-membraned autophagosomes
78
Q

selective autophagy

A
  • selective process
  • defined by type of material being delivered across the lysosomal membrane (chaperone-mediated autophagy)
79
Q

lysosomes

A

membrane-bound organelles of heterogeneous size and morphology that contain acid hydrolases

80
Q

what are the two types of lysosomes, and how do they differ?

A
  1. primary lysosomes: defined as the primary storage site of lysosomal hydrolases
  2. secondary lysosomes: lysosomes engaged in a substrate degradation process
81
Q

endocytosis: definition and 2 important goals

A

invagination of the plasma membrane creating vesicles that serve to internalize extracellular particles and fluids;

2 important functions:

  1. bring material into the cell
  2. recycle the plasma membrane
82
Q

exocytosis

A

when products processed or synthesized by the cell are transported from inside the cell to outside the cell

83
Q
A

Y1 - Histo/Embryo - Daniels (1 decks)

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