1.3

Question 1

Why do phospholipids form a bi-layer in water and describe how they’re arranged

Answer 1

Due to the hydrophilic head and hydrophobic tails
Polar heads face outwards interacting with water outside the cell and inwards interacting with the water in the cytoplasm

Question 2

What is an extrinsic protein

Answer 2

Found on either surface of the bilayer

Question 3

Function of extrinsic proteins

Answer 3

Act as receptors for hormones and as recognition sites

Question 4

What is an intrinsic protein

Answer 4

Proteins that are found within the membrane and extend across both layers

Question 5

What are the 2 kinds of intrinsic proteins

Answer 5

Channel and carrier

Question 6

Why is the membrane said to be representative of the fluid-mosaic model?

Answer 6

Fluid - phospholipids are free to move

Mosaic - random assortment of protein molecules

Question 7

Animal or plant cell membrane contains cholesterol and what does it do

Answer 7

Animal

Stabilises the membrane

Question 8

Function of glycoproteins

Answer 8

Act as antigens

Question 9

Function of glycolipids

Answer 9

Act as receptor sites for molecules eg hormones

Question 10

What kind of molecules pass through simple diffusion

Answer 10

Non-polar molecules and small molecules

They can dissolve in the fatty acid tail and diffuse across the membrane

Question 11

What is diffusion

Answer 11

The passive movement of molecules from a high concentration to a low concentration until they’re equally distributed

Question 12

What does passive mean

Answer 12

Doesn’t require ATP

Question 13

Does simple diffusion transport individual molecules

Answer 13

Yes

Question 14

Factors affecting diffusion

Answer 14

• concentration gradient
• diffusion distance
• surface area of the membrane
• thickness of the exchange surface
• increase in temperature

Question 15

How does increase in concentration gradient affect rate of diffusion

Answer 15

More molecules can diffuse in a given time so collisions with membrane are more likey

Question 16

How does decrease in diffusion distance increase rate of diffusion

Answer 16

Less time for molecules to diffe

Question 17

How does increase in surface area of the membrane increase rate of diffusion

Answer 17

More molecules can diffuse in a given time

Question 18

How does thickness of the exchange surface affect rate of diffusion

Answer 18

Increases with a shorter distance as less time is taken to diffuse

Question 19

How does increase in temperature increase rate of diffusion

Answer 19

Molecules possess more kinetic energy so they move faster and collide with the membrane more frequently

Question 20

Graph of simple diffusion is

Answer 20

Directly proportional

Question 21

What kind of molecules pass through facilitated diffusion?

Answer 21

Polar, water soluble and large

Question 22

What is facilitated diffusion

Answer 22

Passive transfer of molecules/ions down a concentration gradient, across a membrane, by transport proteins in the membrane

Question 23

Which kind of intrinsic protein allows charged molecules through

Answer 23

Channel

Question 24

Which kind of intrinsic protein allows large and water soluble molecules through

Answer 24

Carrier

Question 25

What is active transport

Answer 25

Movement of ions/molecules across the membrane from a low to high concentration against the concentration gradient, this is an ATP requiring process Carrier proteins

Question 26

How does cyanide affect active transport?

Answer 26

Prevents aerobic respiration and ATP production | Without ATP active transport cannot occur

Question 27

Why does the graph of facilitated diffusion and active transport plateau after a while

Answer 27

The proteins are saturated

Question 28

What is co-transport

Answer 28

Type of facilitated diffusion that brings molecules + ions into cells together on the same carrier protein

Question 29

Example of co-transport

Answer 29

Glucose and sodium ions | Mechanism by which glucose is absorbed in the ileum of mammals

Question 30

What is osmosis

Answer 30

the net passive diffusion of water molecules across a selectively permeable membrane from a region of higher water potential to a region of lower water potential.

Question 31

What is water potential

Answer 31

A measure of the tendency of water molecules to move from a high to low concentration of water

Question 32

What is pressure potential

Answer 32

represents the pressure exerted by the cell contents on the cell wall. It can be OkPa or higher.

Question 33

What does a turgid plant cell mean

Answer 33

the plant cell can hold no more | water, as the cell wall cannot expand further.

Question 34

What is a hypertonic solution

Answer 34

Has a lower water potential than the solution inside the cells Water flows out of the cell

Question 35

What is a hypotonic solution

Answer 35

Higher water potential than the solution inside the cell | Water flows into the cell

Question 36

What is an isotonic solution

Answer 36

Has the same water potential to the solution inside the cell | No net water movement

Question 37

What is solute potential

Answer 37

Concentration of dissolved substance in the cell vacuole

Question 38

When is a plant cell said to be flaccid and how does it happen

Answer 38

When plasmolysis is complete | When a plant cell is in a hypertonic solution so the vacuole shrinks and cytoplasm draws away from the cell wall

Question 39

What is the point of incipient plasmolysis

Answer 39

Point at which the cell membrane just begins to move away from the cell wall

Question 40

What is the pressure potential during incipient plasmolysis

Answer 40

0 kPa

Question 41

What is the solute potential during incipient plasmolysis

Answer 41

= water potential

Question 42

Why is being turgor important in plants - especially young seedlings

Answer 42

It provides support | Maintains their shape and holds them upright

Question 43

What % of cells are plasmolysed during incipient plasmolysis

Answer 43

50

Question 44

What will happen to red blood cells in a hypotonic solution

Answer 44

Haemolysis - burst

Question 45

What will happen to red blood cells in a hypertonic solution

Answer 45

Said to be crenated

Question 46

Why will animal cells burst but not plant

Answer 46

Lack of cell wall to resist bursting

Question 47

What are 3 factors that affect permeability of membrane

Answer 47

Temperature , pH and ethanol

Question 48

How does temperature and pH beyond normal range affect permeability

Answer 48

Denature the membrane's proteins which makes gaps in the membrane and it is far more permeable

Question 49

How does ethanol increase permeability of the membrane

Answer 49

Dissolves the lipid components of the membrane and makes holes in it

Question 50

Which kind of transport doesn't transport molecules or ions individually

Answer 50

Bulk - endocytosis and exocytosis

Question 51

What does endocytosis involve

Answer 51

Engulfing of the material by infolding of the plasma membrane bringing it into cell enclosed within a vesicle

Question 52

What are the 2 kinds of endocytosis

Answer 52

Phagocytosis- solid (that are too large) | Pinocytosis - liquid

Question 53

How does exocytosis work

Answer 53

Substances leave the cell after being transported through the cytoplasm in a vesicle

Question 54

Membrane width

Answer 54

7-8 nm