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module 2 > cell membranes > Flashcards

cell membranes Flashcards

1
Q

describe plasma membranes?
( surface of cells )

A

barrier between the cell + its environment - controls what enters + exits

partially permeable - only let some molecules through

can move by active transport / diffusion / osmosis

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2
Q

what do plasma membranes do?

A

allow recognition by other cells
allow cell communication

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3
Q

describe membranes withing the cell?

A

membranes around the organelle
partially permeable

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4
Q

what do membranes within the cell do?

A

divide the cell into compartments - barrier between organelle + cytoplasm - functions more efficient as reactions kept inside

form vesicles to transport substances between different areas of cell

control what enters + exits organelle

site of chemical reactions
e.g inner membrane of mitchondrian - enzymes for respiration

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5
Q

what do membranes within the organelle do?

A

act as a barrier between membrane contents + rest of organelle
e.g thylakoid membranes

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6
Q

what do phospholipid molecules form?

A

bilayer - double layer

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7
Q

why are cell membranes described as having a fluid mosaic structure?

A

phospholipids always moving so bilayer fluid
protein molecules scattered through bilayer like a mosaic

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7
Q

what are glycoproteins + glycolipids?

A

glycoproteins - intrinsic proteins with a polysaccharide chain attached
embedded in cell surface membrane

glycolipids - extrinsic lipids with a polysaccharide chain attached

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7
Q

what are the functions + properties of phospholipids?

A

barrier to dissolved substances

head - hydrophilic
tail - hydrophobic

bilayer - heads face outwards
centre of bilayer - hydrophobic - barrier to water soluble substances

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8
Q

what are the functions + properties of cholesterol?

A

gives membrane stability

lipid in all cell membranes

fit between phospholipids - bind to tails - tails pack closely - membrane less fluid + more rigid

lower temps - prevents phospholipids packing closely - increases fluidity

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9
Q

what are the functions + properties of proteins?

A

controls what enters + exits

form channels - allow small / charged particles through

carrier proteins transport molecules + ions across membrane by active transport + facilitated diffusion

act as receptors for molecules in cell signalling
when a molecules binds to protein - triggers chemical reaction

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10
Q

what are the functions + properties of glycolipids + glycoproteins?

A

acts as receptors for messenger molecules

form hydrogen bonds with surrounding water molecules - stabilises membrane

site of where drugs, hormones, antibodies bind

antigens - cell surface molecules involved in immune response

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11
Q

what is cell signalling?

A

how cells communicate

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12
Q

how does cell signalling work?

A

a cell releases a messenger molecule

molecule travels to another cell

molecule detected by cell as binds to a receptor on its cell membrane

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13
Q

how do cell membrane receptors play an important role in cell signalling?

A

receptor proteins have specific shape - only messenger molecule with complementary shape can bind

different cells have different types of receptors

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14
Q

what is a target cell?

A

a cell that responds to a particular messenger molecule

15
Q

how does the messenger molecule glucagon work?

A

hormone released when not enough glucose in blood - binds to receptors on liver cells - liver cells break down turning glycogen into glucose

16
Q

what do drugs do when they bind to cell membrane receptors?

A

trigger a response in cell / block receptor + prevent it from working

17
Q

how do antihistamines work?

A

histamines released when cell damaged
binds to receptors on surface of other cells - inflammation
antihistamines block histamine receptors - stops inflammation

18
Q

how do you investigate how temperature affects the permeability of the cell membrane?

A

cut 5 equal pieces of beetroot + rinse to remove pigment released when cutting

put each piece in a different test tube + 5 cm water

put each test tube into a water bath at a different temperature ( 10, 20, 30 etc. ) for same length of time

remove beetroot from each tube leaving water

use calorimeter - the higher the permeability of the membrane - more pigment released

19
Q

how does permeability change when temp below 0C?

A

below 0C - phospholipids can’t move as little energy - rigid membrane
channel + carrier proteins deform - increases permeability of membrane
ice crystals can form + pierce membrane - highly permeable

20
Q

what are the 2 types of protein in the membrane?

A

intrinsic proteins - go through both layers of phospholipids
extrinsic proteins - one side of bilayer only

21
Q

what are the 2 intrinsic proteins + give properties?

A

carrier - passive + active transport
involves

22
Q
A
23
Q
A
24
Q

how does permeability change when temp is between 0 and 45C?

A

phospholipids can move around as not packed as tight - partially permeable membrane
as temp increases - phospholipids move more as more energy - increases permeability

25
Q

how does permeablity change when temp above 45C?

A

phospholipid bilayer melts + membrane more permeable
water inside cell expands so pressure on membrane
channel + carrier proteins deform - can’t control what enters / exits - increases permeability

26
Q

how does the solvent surrounding cells affect membrane permeability?

A

increases permeability as they dissolve lipids in cell membrane - loses its structure

26
Q

how can you change the solvent to increase membrane permeability?

A

increase the concentration of solvent

27
Q

what are the 2 main types of protein in the membrane?

A

intrinsic proteins - go through both layers of phospholipid bilayer

extrinsic proteins - go through one side of bilayer only

28
Q

what are carrier proteins?

A

proteins that use active + passive transport
( down a concentration gradient )

uses shape of protein to change ( open / close door )

29
Q

what are channel proteins?

A

proteins with a hole ( channel )
hydrophilic channel - allows passive movement of polar molecules + ions down a concentration gradient
held in position by interactions between hydrophobic core of membrane + hydrophobic outside of protein

30
Q

what is diffusion?

A

net movement of particles both ways from an area of high concentration to low concentration until even distribution

passive process - no energy needed

31
Q

what is the concentration gradient?

A

path from an area of high concentration to low concentration

32
Q

what diffuses through cell membranes?

A

small, non polar molecules - carbon dioxide + oxygen between spaces in phospholipids

water small enough so fits even if polar

33
Q

what 4 factors does the rate of diffusion depend on?

A

concentration gradient - higher = faster rate

thickness of exchange surface - thinner means particles have a shorter distance to travel = faster rate

surface area - larger = faster rate

temperature - warmer = faster rate as particles have more kinetic energy so move faster

34
Q
A

module 2 (3 decks)

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