Membranes

Question 1

Definition of property

Answer 1

A trait that a molcule has which can be used to identify it with.

Question 2

Definition of a component

Answer 2

The different parts that make up a structure.

Question 3

6 membrane components

Answer 3

Phosphlipids / extrinsic proteins / channel proteins / glycoproteins / glycolipid / cholesterol

Question 4

Fucntion of phosphlipids in membranes (5 points)

Answer 4

1. Forms bilayer.
2. Selectively permeable; only allowing non-polar molecules into the cell.
3. Compartmentalisation; maintains different concentrations either side of the membrane.
4. Flexible shape.
5. Within cells; separates metabolic reactions and enzymes inside organelle. Surface for reactions.

Question 5

Describe the function of cholesterol in membranes (2 points).

Answer 5

1. Regulates flexibility.
2. Hydrophobic.

Question 6

Function of proteins in membranes (4 points).

Answer 6

1. Stability to membranes.
2. Can be extrinsic or intrinsic.
3. Channel proteins for polar molecules in facilitated diffusion.
4. Carrier proteins for active transport of polar molecules.

Question 6

Function of proteins in membranes (4 points)

Answer 6

1. Stability to membranes.
2. Can be extrinsic or intrinsic.
3. Channel proteins for polar molecules in facilitated diffusion.
4. Carrier proteins for active transport of polar molecules.

Question 7

Function of glycoproteins in membranes (3 points).

Answer 7

1. Receptor sites for hormones.
2. Act as recognition sites for molecules and cells.
3. Helps cells to attach to each other to form tissue.

Question 8

Explain the effect of increasing temperature on membranes (2 points).

Answer 8

1. A higher temperature gives molecules in the membrane more kinetic energy, so they move faster.
2. The bilayer becomes more fluid which makes the membrane more leaky, increasing permeability.

Question 9

Describe the effect that ethanol has on membranes

Answer 9

Ethanol dissolves lipids causing holes in the membrane allowing molecules to move freely.

Question 10

Explain how solvents cause membranes to leak

Answer 10

Sovents are charged, so form bonds with the hydrophilic heads of the phosphlipids in the cell surface membrane, so the bilayer can’t hold its structure, meaning the contents will leak.

Question 11

Describe passive transport and provide examples (3 points).

Answer 11

1. Does not require energy from the cell in the form of ATP (produced in respiration).
2. Instead relies on kinetic energy of particles.
3. Examples: diffusion / facilitated diffusion / osmosis.

Question 12

Describe active transport and provide examples (2 points)

Answer 12

1. Requires energy in the form of ATP.
2. Examples: active transport / co-transport.

Question 13

Describe how the concentration gradient affects the rate of transport

Answer 13

The greater the difference in concentration inbetween the two sides of the membrane, the faster the rate of transport.

Question 14

Describe and explain how surface area to volume ratio affects the rate of transport

Answer 14

D- The greater the surface area, the faster the rate of trnapsort.
E- This is because more moleules/ions can cross the membrane at any one moment.

Question 15

Describe and explain how the number of proteins affects the rate of transport (2 points).

Answer 15

D- A large number of channel or carrier proteins in the membrane, the fatser the rate of transport.
E- This is because more moelcules/ions can cross the membrane at any one moment.

Question 16

Describe and explain how temperature affects the rate of transport

Answer 16

D- Higher temperatures give molecules or ions more kinetic energy so the faster the rate of transport.
E- Molecules move around faster.

Question 17

Definition of diffusion

Answer 17

Net movement of molecules or ions from a higher concentration to a lower concentration down a concentration gradient until equilibrium. (Passive)

Question 18

Definition of facilitated diffusion (2 points).

Answer 18

1. Net movement of molecules or ions from a higher concentration to a lower concentration down a concenrration gradient until equilibrium.
2. Passive and uses channel/carrier proteins.

Question 19

Definition of osmosis (2 points).

Answer 19

1. The diffusion of water molecules from a higher water potential to a lower water potential gradient until equilibrium.
2. Occurs passively across a membrane or through aquaporins.

Question 20

What is the water potential of pure water?

Answer 20

0kPa

Question 21

Definition of incipient plasmolysis

Answer 21

The protoplast no longer presses on the cell wall.

Question 22

Definition of protoplast

Answer 22

Consists of outer cell-surface membrane, nucleus, cytoplasm and inner vacuole membrane.

Question 23

Definition of turgid

Answer 23

The protoplast is pushed against the cell wall.

Question 24

Definition of active transport (2 points).

Answer 24

1. The movement of ions or molecules from a lower concentration to a higher concentration against a concentration gradient.
2. Uses ATP and carrier proteins.

Question 25

Explain how epithelial cells are specialised to increase the rate of transport (2 points).

Answer 25

1. Large surface area maximises the number of particles that can be absorbed per microvilli.
2. Large, rough endoplasmic reticulum, more protein synthesis means more channel and carrier proteins.