Exchange across cell membranes

Question 1

What is diffusion?

Answer 1

The net movement of particles from a high concentration to a low concentration. Particles move down a concentration gradient.

Question 2

What factors increase the rate of diffusion?

Answer 2

Higher concentration gradient
Thinner exchange surface
Large surface area

Question 3

What is facilitated diffusion?

Answer 3

When large or charged molecules pass through the membrane via carrier proteins and channel proteins.

Question 4

Why are transport proteins needed?

Answer 4

Large molecules can’t fit through and charge particles diffuse too slowly, so they help speed up the rate of diffusion

Question 5

What do carrier proteins do?

Answer 5

Change shape to allow large molecules to fit through

Question 6

What do channel proteins do?

Answer 6

Are pores in the membrane to allow charge particles to diffuse

Question 7

Which increases the rate of facilitated diffusion?

Answer 7

Higher concentration
Increased number of carrier and channel proteins in membrane

Question 8

What is osmosis?

Answer 8

Diffusion of water through a partially permeable membrane from a high concentration to a low concentration

Question 9

What is water potential?

Answer 9

The likelihood water molecules will diffuse in and out of a solution.
Higher water potential = less negative
Lower water potential = more negative

Question 10

What will adding a solute to water do to the water potential?

Answer 10

Lower the water potential

Question 11

What increases the rate of osmosis?

Answer 11

Higher water potential gradient
Thin membrane
Large surface area

Question 12

Explain isotonic, hypertonic and hypotonic solutions

Answer 12

Isotonic = no net movement
Hypertonic = net movement out of the cell
Hypotonic = net movement into the cell

Question 13

What is active transport?

Answer 13

An active process the moves solutes from a low concentration to a high concentration

Question 14

What does active transport require?

Answer 14

ATP (hydrolysis reaction)

Question 15

What transporter protein is involved in active transport?

Answer 15

Carrier proteins

Question 16

What are co-transporters?

Answer 16

A type of carrier protein

Question 17

What do co-transporters do?

Answer 17

Bind 2 molecules at the same time . The concentration of one of the molecules is used to move the other molecule against its concentration gradient

Question 18

What increases the rate of active transport?

Answer 18

Faster speed of individual carrier proteins
High numbers of carrier proteins
High rate of respiration
Availability of ATP

Question 19

Explain the process of glucose and sodium ions

Answer 19

1. Sodium ions actively transport out of the epithelial cells into the blood via a sodium potassium pump
2. This creates a concentration gradient and causes ions to diffuse from lumen of ileum to epithelial cells down the concentration gradient by sodium glucose co-transporter proteins
3. The co-transporters carry glucose into cell with the sodium. This increases the concentration of glucose in the cell
4. Glucose diffuses out cell into the blood down the concentration gradient through a protein channel by facilitate diffusion