CB23 Membrane Transport

Question 1

Explain the requirement for membrane transport

Answer 1

Movement of solutes & molecules across membranes is essential for:
- absorption / uptake of ions & nutrients
- excretion of metabolic waste products
- secretion of extracellular proteins
- concentrating molecules in specific compartments

Question 2

Distinguish between passive & active transport

Answer 2

Passive transport:
Solute moves down its concentration / electrochemical gradient
Doesn’t require energy (ATP)
Achieves equilibrium

Active transport:
Solute moves against its concentration / electrochemical gradient
Requires energy (ATP)
Maintains imbalance

Question 3

Understand the concept of facilitated diffusion, give examples

Answer 3

Membrane-spanning proteins act as pores to facilitate solute movement through the membrane down the concentration gradient

• carrier proteins
• ion channels

Question 4

Describe the main type of ion channels

Answer 4

Voltage-gated ion channels
Ligand-gated ion channels
Mechanical “stretch” ion channels
“leak” ion channels

Question 5

Explain the concept of active transport, with examples of primary & secondary active transporters

Answer 5

Ions are actively transported against the ionic gradient
Energy required is obtained by the hydrolysis of ATP

e.g.
Sodium potassium pump, sodium glucose symporter
Sodium potassium pump, sodium hydrogen antiporter