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BIOLOGY > 2B Cell membrane > Flashcards

2B Cell membrane Flashcards

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1
Q

basic structure of cell membrane

A

composed of lipids proteins and carbohydrates

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2
Q

name cell membranes structure

A

fluid mosaic

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3
Q

in fluid mosaic model what forms bilayer

A

phospholipids

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4
Q

why is the structure of cell membrane described as fluid

A

as the phospholipids are constantly moving

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5
Q

where are cholesterol molecules present in cell membrane

A

within the bilayer

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6
Q

why is the cell membrane described as mosaic

A

proteins a scattered throughout bilayer like mosaic

these include channel proteins, carrier proteins and receptor proteins

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7
Q

what do channel proteins and carrier proteins in bilayer allow

A

large molecules and ions to pass through membrane

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8
Q

what does receptor proteins allow in the bilayer

A

receptor proteins on the cell membrane allow cell to detect chemicals released from other cells.the chemicals signal cell to respond in some way

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9
Q

example of chemicals to receptor protein signalling cell to respond

A

hormone insulin binds to receptor proteins on liver cells which tells cells to absorb glucose

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10
Q

how are the proteins movement in the cell membrane varried

A

some can move sideways through bilayer whereas others are in fixed positions

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11
Q

what are glycoproteins

A

proteins with polysaccharide chain attached

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12
Q

what are glycolipids

A

lipids with polysaccharide chain attached

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13
Q

descrive phospholipids positioning in bilayer

A

head is hydrophilic
tail is hydrophobic
heads face out in bilayer towards the water
center is hydrophobic so doesn’t allow water soluble substances through

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14
Q

what is cholesterol

A

type of lipid which is present in all cell membranes except bacterium membranes

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15
Q

describe cholesterol in the cell membrane

A

fits between phospholipids binding to their hydrophobic tails causing them to pack closer together
this restricts movement of phospholipids making membrane less fluid and more rigid

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16
Q

how is cholesterols useful in animal cells

A

helps maintain shape of cell which don’t have cell walls

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17
Q

describe membrane permeability at temp below 0

A

phospholipids don’t have much energy so can’t move much
packed close so membrane is rigid
channel/carrier proteins deform increasing permeability
crystals may form

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18
Q

describe membrane permeability at 0-45

A

Phospholipids can move around and aren’t packed tightly together
membrane is partially permeable
temp increases phospholipids move more as they have a energy increasing permeability

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19
Q

describe membrane permeability over 45

A

phospholipid bilayer starts to breakdown
becomes more permeable
water expands putting pressure
carrier and channel proteins deform

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20
Q

diffusion définition

A

the net movement of particles from an area of high concentration to lower concentration

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21
Q

why is diffusion described as a passive process

A

no energy in form of ATP is needed

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22
Q

what’s simple diffusion

A

when molecules diffuse directly through a membrane

23
Q

what’s facilitated diffusion

A

diffusion using carrier proteins and protein channels

24
Q

what uses facilitated diffusion

A 
larger molecules (glucose, amino acids )
charged (ions /polar) as they are water soluble so would otherwise diffuse very slowly as bilayer is hydrophobic
25
Q

how does facilitated diffusion using carrier proteins work

A

1) large molecule attacches to carrier protein
2) protein changes shape
3) this releases molecule on opposite side of membrane

26
Q

how does facilitated diffusion using protein channels work

A

channel protein form pores for charged particles to diffuse through
different channel proteins facilitate the diffusion of different charged particles

27
Q

how to concentration gradient effect simple diffusion

A

Centration gradient means faster rate of diffusion
difference in concentration between both sides of membrane decreases until equilibrium so diffusion slows down over time

28
Q

how thickness of exchange surface effects simple diffusion

A

thinner exchange surface faster rate of diffusion

29
Q

how does surface area effect simple diffusion

A

larger surface area faster rate of diffusion

30
Q

what is microvilli

A

(found in epthileal cells and small intestine) projections formed by cell surface membrane folding in on its self

31
Q

what does microvilli do

A

gives cell a large surface area (in human cells by 600x)

larger surface area means more particles are exchanged in the same time

32
Q

how concentration gradient effects facilitated diffusion

A

Higher the concentration gradient faster rate of facilitated diffusion
\as equilibrium reached rate of diffusion levels off

33
Q

how does number of channel or carrier proteins effect facilitated diffusion

A

when all the proteins are in use the rate of diffusion cannot increasingly any more
greater number of channel or carrier proteins means faster rate of diffusion

34
Q

what are aquaporins

A

Channel proteins that allow facilitated diffusion of water some kidney cells are adapted to have lots of Aquaporins
allows cell to absorb water which would otherwise be excreted (180litre)

35
Q

define osmosis

A

diffusion of water molecules across a partially permeable cell membrane from an area of higher water potential to an area of lower water potential

36
Q

what is water potential

A

the potential or likelihood of water molecules to diffuse out or into a solution

37
Q

what has highest water potential

A

pure water

38
Q

what is isotonic

A

if two solutions have same water potential

39
Q

how does the water potential gradient effect osmosis

A

higher water potential gradient faster rate of osmosis

40
Q

how does the thickness of exchange surface effect osmosis

A

thinner exchange surface faster rate of osmosis

41
Q

how does surface area effect osmosis

A

larger surface area the faster rate of osmosis

42
Q

what is active transport

A

uses energy to move molecules and ions across membranes usually against a concentration gradient

43
Q

how a carrier proteins involved in active transport

A

a molecule attaches to the carrier protein the protein changes shape and this moves molecule across membrane releasing it to other side

44
Q

how do the concentration gradients differ from facilitated diffusion and active transport

A

active transport - low to high

facilitated diffusion- hight to low

45
Q

how does energy requirements differ with facilitated diffusion and active transport

A

facilitated diffusion- doesn’t require energy

active transport - requires energy in form of atp

46
Q

what are co-transporters

A

type of carrier protein
bind two molecules at a time
conc grad of one of the molecules is used to move other molecule against its own conc grad

47
Q

how does speed of individual carrier proteins effect rate of active transport

A

faster they work the faster rate of active transport

48
Q

how does number of carrier proteins present effect the rate of active transport

A

more proteins there are faster rate of active transport

49
Q

how does rate of respiration and availability of atp effect rate of active transport

A

if respiration is inhibited then active transport cannot take place

50
Q

how is glucose absorbed by the ileum

A

by co transport as the conc of glucose is too low for glucose to diffuse into blood so glucose is absorbed from lumen of ileum by co transport

51
Q

first step of glucose absorption by co transport

A

sodium ions actively transported out of ileum epithelial cells into blood by sodium phosphate pump
creating conc grad -higher conc of sodium ions in lumen of ileum than inside cell

52
Q

second step of glucose absorbtion by co transport

A

first step causes sodium ions to diffuse from lumen in ileum to epithelial cell down Conc grad
They do this via the sodium glucose cotransporter proteins

53
Q

third step of glucose absorbtion by co transport

A

Cotransporter carries glucose into cell with sodium as a result the concentration of glucose inside cell increases

54
Q

Fourth step of glucose absorption by co transport

A

Grieco diffusers out of cell into blood down a concentration gradient through protein channel by facilitated diffusion

BIOLOGY (20 decks)

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