Unit 1- Membrane Transport Flashcards
Resting Cell Charge
Inside is negative relative to outside. about -70mV
Ion gradients at rest
Na+: High outside, low inside.
K+: High inside, low outside.
Transport types
Passive: No energy (diffusion, facilitated diffusion).
Active: Requires energy (pumps).
Diffusion Limitations
Size, charge, and solubility affect permeability.
Channels vs Pumps
Channels: Facilitated diffusion, no energy.
Pumps: Active transport, require energy.
Channel Gating
Voltage-gated: Respond to voltage changes.
Ligand-gated: Respond to ligand binding.
Mechanosensitive: Respond to mechanical forces.
Voltage-gated channel selectivity
Based on ion size and charge.
Voltage response mechanism
Voltage-sensing domains change conformation in response to membrane potential changes.
Channel vs Carrier
Channel: Passively facilitates ion movement.
Carrier: Binds and changes shape to move substances
Carrier against gradient
Can use secondary active transport, leveraging ion gradients.
Channel/Transporter structures:
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.