transport across cell membranes

Question 1

function of the cell membrane

Answer 1

controls which substances pass into + out of cell

Question 2

3 functions of internal membranes

Answer 2

compartmentalisation
site for biochemical reactions
controls which substances pass into and out of organelles

Question 3

5 main molecular components of a membrane

Answer 3

phospholipids
proteins
glycoproteins
glycolipids
cholesterol

Question 4

3 functions of phospholipids

Answer 4

allow lipid soluble substances to enter and leave cell
prevent water soluble substances entering or leaving cell
makes membrane flexible and self sealing

Question 5

2 functions of extrinsic proteins

Answer 5

provide mechanical support/adhesion
act as receptors for molecules

Question 6

2 functions of intrinsic proteins

Answer 6

form protein channels
form carrier proteins

Question 7

3 functions of cholesterol

Answer 7

reduces lateral movement of molecules
makes the membrane less fluid
prevents leakage from cell

Question 8

3 functions of glycolipids

Answer 8

act as recognition site
helps maintain membrane stability
helps attach cells together to form tissues

Question 9

3 functions of glycoproteins

Answer 9

act as recognition sites
help cells attach to each other to form tissues
used in cell recognition

Question 10

define diffusion

Answer 10

the net movement of molecules or ions from a region of high concentration to an area of low concentration, until at equilibrium.

Question 11

3 factors affecting rate of diffusion

Answer 11

surface area
difference in concentration
thickness of membrane

Question 12

define osmosis

Answer 12

the passage of water molecules from a solution of high water potential to a solution of low water potential through a selectively permeable membrane.

Question 13

define hypotonic

Answer 13

less concentrated

Question 14

define hypertonic

Answer 14

more concentrated

Question 15

define isotonic

Answer 15

at equilibrium

Question 16

define water potential

Answer 16

the pressure created by water molecules trying to diffuse out of a solution down a gradient from a higher water potential to a lower water potential.

Question 17

what has high water potential

Answer 17

a dilute solution as it has many free water molecules so water is more likely to move

Question 18

what is the water potential to f pure water

Answer 18

0

Question 19

what is a protoplast

Answer 19

the entire cell is excluding the cell wall

Question 20

what is incipient plasmolysis

Answer 20

the point where plasmolysis takes place and half the cells are plasmolysed, half are not

Question 21

what happens when an animal cell is in a solution of high water potential

Answer 21

cell bursts open

Question 22

what happens when animal cell is in a solution of low water potential

Answer 22

cell shrinks and shrivels

Question 23

what happens when a plant cell is in a solution of high water potential

Answer 23

protoplast is pushed tight against cell wall

Question 24

what happens when a plant cell is in a solution with low water potential

Answer 24

protoplast shrinks away from cell wall
(plasmolysed)

Question 25

what particles does a channel protein transport

Answer 25

small charges substances (usually ions)

Question 26

what do channel proteins form

Answer 26

water filled pores lined with polar groups (so hydrophilic)

Question 27

how do cells use channel proteins to control entry and exit

Answer 27

most channels are gated

Question 28

what do carrier proteins transport

Answer 28

larger molecules such as glucose and amino acids are taken across

Question 29

how does a carrier protein work

Answer 29

is able to bind with a specific shaped molecule
the carrier changes shape to release the molecules the other side of the membrane

Question 30

define active transport

Answer 30

the movement of molecules or ions into or out of a cell from a region of lower concentration to a region of higher concentration using ATP and carrier proteins.

Question 31

4 ways that active transport differs from passive transport

Answer 31

requires energy in the form of ATP
goes against the concentration gradient
only uses carrier proteins
process is very selective

Question 32

what is co transport

Answer 32

where 2 substances are simultaneously transported across a membrane by 1 protein

Question 33

define symport

Answer 33

2 molecules moved together from one area to another

Question 34

define anti port

Answer 34

1 substance going in one direction, 1 in another

Question 35

example of anti port

Answer 35

sodium potassium pump

Question 36

2 adaptations of the ileum absorption

Answer 36

• large surface area for co transport proteins to fit on the membrane
• lots of mitochondria to produce ATP to provide energy for absorption

Question 37

what is cotransported in the ileum

Answer 37

glucose molecules with sodium ions

Question 38

what happens during co transport in the ileum

Answer 38

Na+ diffuses down the concentration gradient into the epithelial cell. This pulls glucose molecules into the epithelial cell against the concentration gradient.
To maintain a low Na+ concentration inside cells Na+ pumped into blood using sodium potassium pumps.
Glucose moves into blood down the concentration gradient by facilitated diffusion.

Question 39

what does the sodium potassium pump require

Answer 39

ATP

Question 40

does the sodium potassium pump go with or against concentration gradient

Answer 40

both potassium and sodium go against their concentration gradient

Question 41

what direction does potassium go in the pump

Answer 41

into the cell from the blood

Question 42

which direction does sodium go in the pump

Answer 42

goes from the cell into the blood