membrane stuff

Question 1

what are cell surface membranes mainly comprised of?

Answer 1

phospholipids

Question 2

why can phospholipids form bi layers?

Answer 2

as they have a polar head and a non polar tail

Question 3

what is the function of cholesterol

Answer 3

regulates membrane fluidity

Question 4

name two things glycoproteins and glycolipids do

Answer 4

.act as self antigens

.help join cells together

Question 5

why is diffusion a passive process

Answer 5

as it only requires the energy of the particles themselves and no energy in the form of ATP

Question 6

what is osmosis

Answer 6

osmosis-movement of water across a partially permeable membrane from high water potential to low water potential until dynamic equilibrium has been reached.

Question 7

what are the units of water potential

Answer 7

Kpa

Question 8

what is the highest water potential?

Answer 8

0Kpa

Question 9

what is active transport?

Answer 9

the movement of partcles from a low to high concentration

Question 10

why is active transport an active process?

Answer 10

As it requires energy in the form of ATP

Question 11

how phospholipids arranged in the bilayer of a membrane?

Answer 11

the hydrophobic tails point inwards the hydrophillic heads point outwards

Question 12

name three factors that affect rate of diffusion

Answer 12

temperature,surface area,diffusion distance

Question 13

what happens to a red blood cell if it loses too much water

Answer 13

water leaves the cell and the cell shrinks

Question 14

what happens to a red blood cell if it gains too much water

Answer 14

it undergoes haemolysis(bursts)

Question 15

what is the function of cell surface membranes

Answer 15

they are a barrier between the cell and it’s enviroment

they control what substances can enter and exit the cell

Question 16

how does the cell surface achieve it’s function

Answer 16

it’s partially permemable they let some molecuels through but not others.

Question 17

name three ways substances can pass through a cell surface membrane

Answer 17

osmosis,diffusion and active transport

Question 18

what is the function of channel and carrier proteins do in the cell membrane

Answer 18

allow large molecules and ions to pass through the membrane

either by facilitated diffusion or active transport

Question 19

how does the phospholipid bilayer allow non-polar/hydrophobic molecules to pass through the bilayer

Answer 19

the centre of the bilayer is hydrophobic

so it doesn’t allow water soluble substances to diffuse through it

Question 20

outline how carrier proteins carry out facilitated diffusion

Answer 20

a large molecule attaches to a carrier protein in the membrane
then the protein changes shape
this releases the molecule on the other side of the membrane

Question 21

outline how channel proteins work

Answer 21

they form pores in the membrane for charged particles to diffuse through

Question 22

name two factors affecting the rate of facilitated diffusion

Answer 22

the concentration gradient

the number of channel or carrier proteins

Question 23

how are cells adapted for rapid exhange

Answer 23

by large number of channel/carrier proteins in their membrane
by having a large surface area