2.1.5

Question 1

role of membranes (5)

Answer 1

compartmentalisation
isolate reactions
attachment sites in cell-cell signalling
control what goes in/out
create concentration/ electrochemical/ water potential gradient

Question 2

FMM contains

Answer 2

extrinsic proteins
intrinsic proteins
plb
glycolipids
glycoproteins
cholesterol

Question 3

extrinsic protein summary

Answer 3

protein fixed in membrane, transmembrane, typically channel or carrier

Question 4

intrinsic protein summary

Answer 4

protein fixed in membrane, one side only, typically enzymes

Question 5

phospholipid summary

Answer 5

hydrophyllic phosphate head attached to glycerol attached to hydrophobic fatty acid tails

Question 6

why phospholipid forms bilayer

Answer 6

• hydrophyllic phosphate heads attracted to aq solution
• hydrophobic fatty acid tails repelled by aq solution
• tissue fluid and cytoplasm are aq, phospholipids orientate to form two layers with heads outward and tails inward

Question 7

how does cholesterol control fluidity?

Answer 7

increases stability when hot as bonds pull cholesterol and phospholipid together
increases fluidity when cold as cholesterol disrupts close packing of phospholipids

Question 8

cholesterol structure and function

Answer 8

regulates fluidity/ stability
regulates permeability
provides mechanical strength
4 carbon rings, one OH

Question 9

glycoproteins structure and function

Answer 9

saccharide attached to embedded protein
receptor for cell-cell signalling (e.g. hormones)
cell adhesion

Question 10

glycolipid structure and function

Answer 10

saccharide attached to lipid
antigens
cell recognition

Question 11

whats a micelle

Answer 11

single ring of phospholipids

Question 12

factors affecting the rate of diffusion (7)

Answer 12

temperature
diffusion distance
concentration gradient
surface area : volume
particle size
pH (denatures proteins and plb)
number of carrier/ channel (only facilitated)

Question 13

simple diffusion summary

Answer 13

natural kinetic energy causes random movement until equilibrium through the plb
moves small, non-polar/charge, lipid soluble molecules

Question 14

facilitated diffusion summary

Answer 14

same as simple but through channel or carrier
moves ions/ polar, water soluble, large molecules

Question 15

diffusion definition

Answer 15

passive net movement of molecules from a higher to lower concentration until equilibrium

Question 16

osmosis definition

Answer 16

net passive movement of water across a partially permeable membrane from an area of high to low water potential

Question 17

water potential definition

Answer 17

relative tendency for water to move and the pressure exerted on membrane in kPa

Question 18

plant cell in hypertonic

Answer 18

low water potential, water leaves vacuole, protoplast and vacuole shrink, less pressure on cell wall
cell is plasmolysed

Question 19

animal cell in hypertonic

Answer 19

low water potential, water leaves, cell shrivels (crenation)

Question 20

animal cell in hypotonic

Answer 20

high water potential, water enters and cell swells and bursts (lysis)

Question 21

plant cell in hypotonic

Answer 21

high water potential, water enters vacuole, pressure builds, cell becomes turgid as cell wall

Question 22

isotonic definition

Answer 22

same water potential, no change

Question 23

membrane permeability factors (5)

Answer 23

temperature
cholesterol
phosphoLIPIDS
solvents
pH

Question 24

temperature on membrane permeability

Answer 24

melts or freezes PLB

Question 25

cholesterol on membrane permeability

Answer 25

cold - disrupts regular shape of phospholipids so it doesnt freeze hot - hold together plb with ester bonds depends on quantity of cholesterol

Question 26

plb fats on membrane permeability

Answer 26

unsaturated has kinks, less regular shape, more space in plb, more permeable and vice versa

Question 27

pH on membrane permeability

Answer 27

denatures membrane proteins, less f.d.

Question 28

solvents on membrane permeability

Answer 28

less polar so disrupt plb so more permeable e.g. alcohol and benzene

Question 29

bulk transport summary

Answer 29

passive (no ATP in movement), moves parts of cells/ bacteria/ hormones/ enzymes/ macromolecules

Question 30

endocytosis summary

Answer 30

into cells pino for liquid, phago for solid csm invaginates at contact membranes enfold and fuse vesicle pinches off and moves

Question 31

exocytosis summary

Answer 31

out of cells secretory vesicle from golgi moves and fuses to csm releases substances to ECF