Topic 5: Membrane Transport Flashcards
At rest what charge does the inside of the cell have?
Negative membrane potential
What is the concentration gradient of NA+ and of K+?
More sodium outside the cell and more potassium inside the cell
What are the three types of membrane transport?
Diffusion: Through the membrane
Channels: Passageway or chemical movement down the concentration gradient
Carriers: Proteins must bring and release the transported molecule
Pump: Active transport - needs energy
Why can’t everything diffuse across the membrane?
Ions and larger uncharged molecules can’t diffuse across the membrane because cannot go through nonpolar part of the membrane
Do channels require energy?
No. Channels more down the concentration gradient
Do pumps require energy?
Yes pumps require ATP because it moves against the concentration gradient
What re the three different ways that we can use to control when a channel is open or closed?
Leak channels: Always open
Voltage-gated channels: Open/close in response to changes in membrane potential
Ligand Gated channels: Open/close hen bound by a specific chemical substance
Mechanically gated channels: Open/close in response to a physical force on the membrane
What component of a voltage-gated channel structure creates a selectivity of specific ions?
P loop is the selectivity filter the size of the channel power is designed to just match the diameter of the dehydrated ion
How is a channel different from a carrier?
Channel: can always be open. Involve the free movement of ions through the membrane without binding
Carriers: Moving one thing down its concentration gradient. Ligand binding site between the domains
How can a carrier move something against its concentration gradient without using energy?
Facilitated diffusion. Proteins powered by ATP move substances up a concentration gradient.
Difference between T domains and A domains on ABC pump?
T domains: transmembrane domains
A domain: ATP binding domains must face intracellular space to allow the binding of ATP
Why does the Na+/K+ pump require energy?
Because it actively transports ions against their concentration gradient. Always functioning to ensure the correct concentrations.
What component of a voltage-gated channel structure responds to a voltage change in the cell? How does this work?
Helix 4 moves away from the cytol opening the pore and allowing ions through
