Unit 1- Membrane Transport

Question 1

Resting Cell Charge

Answer 1

Inside is negative relative to outside. about -70mV

Question 2

Ion gradients at rest

Answer 2

Na+: High outside, low inside.
K+: High inside, low outside.

Question 3

Transport types

Answer 3

Passive: No energy (diffusion, facilitated diffusion).
Active: Requires energy (pumps).

Question 4

Diffusion Limitations

Answer 4

Size, charge, and solubility affect permeability.

Question 5

Channels vs Pumps

Answer 5

Channels: Facilitated diffusion, no energy.
Pumps: Active transport, require energy.

Question 6

Channel Gating

Answer 6

Voltage-gated: Respond to voltage changes.
Ligand-gated: Respond to ligand binding.
Mechanosensitive: Respond to mechanical forces.

Question 7

Voltage-gated channel selectivity

Answer 7

Based on ion size and charge.

Question 8

Voltage response mechanism

Answer 8

Voltage-sensing domains change conformation in response to membrane potential changes.

Question 9

Channel vs Carrier

Answer 9

Channel: Passively facilitates ion movement.
Carrier: Binds and changes shape to move substances

Question 10

Carrier against gradient

Answer 10

Can use secondary active transport, leveraging ion gradients.

Question 11

Channel/Transporter structures:

Answer 11

Ion Channels:
–> Membrane-spanning proteins with selective pores for ions (Na⁺, K⁺, Ca²⁺, Cl⁻).
—>Gating: Voltage, Ligand, Mechanical.

Transporters
–>Types: Uniporters, Symporters, Antiporters.
—>Undergo conformational changes to transport molecules (e.g., Na⁺/K⁺ pump).

Aquaporins
–>Water-specific channels with tetrameric structure.

Symporters/Antiporters
–>Symporters: Transport two molecules in the same direction.
–>Antiporters: Transport two molecules in opposite directions.