3.2.3 Transport across cell membranes

Question 1

what is the cell surface membrane

Answer 1

a barrier between the cell and its environment
controls what enters and leaves the cell
partially permeable

Question 2

why does the cell membrane have a Fluid Mosaic Structure

Answer 2

fluid- phospholipids are able to move
mosaic- made up of many components such as the phospholipid bilayer, glycoproteins and glycolipids

Question 3

how are phospholipids arranged

Answer 3

they are arranged in a bilayer

Question 4

what is meant by hydrophobic

Answer 4

it repels water

Question 5

what is meant by hydrophilic

Answer 5

it attracts water

Question 6

what part of the phospholipid is hydrophopic

Answer 6

the fatty acid tail

Question 7

what part of the phospholipid is hydrophilic

Answer 7

the phosphate head

Question 8

what type of molecules are allowedd to move through the phospholipid bilayer by

Answer 8

non-polar molecules
lipid soluble molecules
small molecules

Question 9

what does the bilayer restrict

Answer 9

the movement of large/polar molecules

Question 10

what do channel proteins allow the movement of

Answer 10

allow the movement of water-soluble/ polar molecules

Question 11

what do carrier proteins allow the movement of

Answer 11

movement of molecules against concentration gradient using ATP

Question 12

what is cholestral made up of

Answer 12

lipid

Question 13

what is the role of cholestral

Answer 13

the make the membrane rigid by restricting the lateral movement of phospholipids

Question 14

where in the cell membrane is cholestral found

Answer 14

they bind to the hydrophobic tail

Question 15

what happens to the cell membrane when the temperature is increased

Answer 15

thee membrane permeability increases

Question 16

explain what happens to the cell membrane when the temperature is really really high (45 degrees)

Answer 16

phospholipids have more kinetic energy
-the bilayer starts to melt
- the membrane become more permeable
- water in the cell expands
- channel and carrier proteins denature.
- so the cant control what goes in and out

Question 17

explain what happens to the cell membrane when the temperature are below 0 degrees

Answer 17

-phospholipids dont have enough energy
-so unable to move as they are packed together

Question 18

what are the 5 ways molecules can move across the membrane

Answer 18

-simple diffusion
-facilitated diffusion
-active transport
-osmosis
-co-transport

Question 19

how do molecules move into the membrane by simple diffusion

Answer 19

from high concentration to low concentration down the concentration gradient
across the membrane

Question 20

is diffusion an active or passive process

Answer 20

passive

Question 21

what does facilitated diffuision use

Answer 21

carrier proteins
protein channels

Question 22

describe how molcules move through carrieer proteins

Answer 22

• they attach to the carrier protein
• protein changes shape
• molecule is released to opposite side of membrane

Question 23

what do channel proteins allow the movement of

Answer 23

charged particles

Question 24

how does a high concentration gradient affect the rate of simple diffucion

Answer 24

-faster rate of diffusion
- so that equilibrium is reached

Question 25

what is the effect of a thin exchange surface on the rate of diffusion

Answer 25

- a thin exchange surface (means particles have short distance to travel) so faster rate of diffusion

Question 26

what is the affect of a large surface during simple diffusion

Answer 26

the rate of diffusion is faster

Question 27

why does the presence of microvilli increase the surface area for faster diffusion

Answer 27

allows more particles to exchange in the same amount of time

Question 28

what is the effect of microvili on the rate of diffusion

Answer 28

they increase it

Question 29

what does facilittated diffusion depend on

Answer 29

the number of carrier or channel proteins

Question 30

what happens when carrier proteins and chaneels are in use

Answer 30

facilitated diffusion cant happen quickly

Question 31

what does many carrier proteins and channels allow

Answer 31

faster rate of facilitated diffusion

Question 32

describe thee movement of water molecules across a partially permeable membrane

Answer 32

water moves down water potential gradient from an area of high water potential to areas of low water potential

Question 33

how does the water potential decrease

Answer 33

when a solute is added

Question 34

what is the water potential of pure water

Answer 34

0

Question 35

two solutions with the same water potential is referred to as..?

Answer 35

isotonic

Question 36

what factors affect the rate of osmosis

Answer 36

-the water potential gradient - tickness of the exchange surface -surface are of the exchange surface

Question 37

what is active transport

Answer 37

-movement of molecules against a concentration gradient -requiring energy in the form of ATP -low to high conc

Question 38

is active transport an active or passive proccess

Answer 38

active process

Question 39

what proteins is usually involved in active transport

Answer 39

carrier protein

Question 40

expalin how molecules are actively transported across the membrane

Answer 40

-molecule attaches to carieer protein - protein changes shape and ATP splits into ADP + Pi . the energy changes the tertiary structure of protein. to allow solutes to be transported

Question 41

what effects the rate of active transport

Answer 41

speed of individual carrier proteins -number of carrieer proteins - rate of respiration

Question 42

when the speed of the carrier proteins are increased what happens to the rate of active transport

Answer 42

they work faster

Question 43

what happens when there are more carrieer proteins

Answer 43

active transport occurs at a faster rate

Question 44

what happens when respiation is inhibited

Answer 44

no ATP produced no active transport