2B Cell membrane

Question 1

basic structure of cell membrane

Answer 1

composed of lipids proteins and carbohydrates

Question 2

name cell membranes structure

Answer 2

fluid mosaic

Question 3

in fluid mosaic model what forms bilayer

Answer 3

phospholipids

Question 4

why is the structure of cell membrane described as fluid

Answer 4

as the phospholipids are constantly moving

Question 5

where are cholesterol molecules present in cell membrane

Answer 5

within the bilayer

Question 6

why is the cell membrane described as mosaic

Answer 6

proteins a scattered throughout bilayer like mosaic

these include channel proteins, carrier proteins and receptor proteins

Question 7

what do channel proteins and carrier proteins in bilayer allow

Answer 7

large molecules and ions to pass through membrane

Question 8

what does receptor proteins allow in the bilayer

Answer 8

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

Question 9

example of chemicals to receptor protein signalling cell to respond

Answer 9

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

Question 10

how are the proteins movement in the cell membrane varried

Answer 10

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

Question 11

what are glycoproteins

Answer 11

proteins with polysaccharide chain attached

Question 12

what are glycolipids

Answer 12

lipids with polysaccharide chain attached

Question 13

descrive phospholipids positioning in bilayer

Answer 13

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

Question 14

what is cholesterol

Answer 14

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

Question 15

describe cholesterol in the cell membrane

Answer 15

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

Question 16

how is cholesterols useful in animal cells

Answer 16

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

Question 17

describe membrane permeability at temp below 0

Answer 17

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

Question 18

describe membrane permeability at 0-45

Answer 18

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

Question 19

describe membrane permeability over 45

Answer 19

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

Question 20

diffusion définition

Answer 20

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

Question 21

why is diffusion described as a passive process

Answer 21

no energy in form of ATP is needed

Question 22

what’s simple diffusion

Answer 22

when molecules diffuse directly through a membrane

Question 23

what’s facilitated diffusion

Answer 23

diffusion using carrier proteins and protein channels

Question 24

what uses facilitated diffusion

Answer 24

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

Question 25

how does facilitated diffusion using carrier proteins work

Answer 25

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

Question 26

how does facilitated diffusion using protein channels work

Answer 26

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

Question 27

how to concentration gradient effect simple diffusion

Answer 27

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

Question 28

how thickness of exchange surface effects simple diffusion

Answer 28

thinner exchange surface faster rate of diffusion

Question 29

how does surface area effect simple diffusion

Answer 29

larger surface area faster rate of diffusion

Question 30

what is microvilli

Answer 30

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

Question 31

what does microvilli do

Answer 31

gives cell a large surface area (in human cells by 600x) | larger surface area means more particles are exchanged in the same time

Question 32

how concentration gradient effects facilitated diffusion

Answer 32

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

Question 33

how does number of channel or carrier proteins effect facilitated diffusion

Answer 33

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

Question 34

what are aquaporins

Answer 34

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)

Question 35

define osmosis

Answer 35

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

Question 36

what is water potential

Answer 36

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

Question 37

what has highest water potential

Answer 37

pure water

Question 38

what is isotonic

Answer 38

if two solutions have same water potential

Question 39

how does the water potential gradient effect osmosis

Answer 39

higher water potential gradient faster rate of osmosis

Question 40

how does the thickness of exchange surface effect osmosis

Answer 40

thinner exchange surface faster rate of osmosis

Question 41

how does surface area effect osmosis

Answer 41

larger surface area the faster rate of osmosis

Question 42

what is active transport

Answer 42

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

Question 43

how a carrier proteins involved in active transport

Answer 43

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

Question 44

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

Answer 44

active transport - low to high | facilitated diffusion- hight to low

Question 45

how does energy requirements differ with facilitated diffusion and active transport

Answer 45

facilitated diffusion- doesn't require energy | active transport - requires energy in form of atp

Question 46

what are co-transporters

Answer 46

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

Question 47

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

Answer 47

faster they work the faster rate of active transport

Question 48

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

Answer 48

more proteins there are faster rate of active transport

Question 49

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

Answer 49

if respiration is inhibited then active transport cannot take place

Question 50

how is glucose absorbed by the ileum

Answer 50

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

Question 51

first step of glucose absorption by co transport

Answer 51

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

Question 52

second step of glucose absorbtion by co transport

Answer 52

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

Question 53

third step of glucose absorbtion by co transport

Answer 53

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

Question 54

Fourth step of glucose absorption by co transport

Answer 54

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