Membrane Transport

Question 1

Ion Channels

Answer 1

Move ions down conc. gradient. Do NOT undergo conformational change. Highly selective (distinguish b/ Na+ and K+). Voltage and Ligand-gated

Question 2

Ligand-Gated

Answer 2

Activated by ligand binding. Ionotropic receptors

Question 3

Metabotrophic Receptors

Answer 3

G-protein coupled

Question 4

Resting Potential

Answer 4

Electrical potential across the cell membrane results from the uneven distribution of ions b/ inside and outside of the neuron. Inside is more - charged than outside. Maintained by an ATP-dependent (Na+/K+ pump) that keeps Na+ low and K+ high inside the neuron.

Question 5

Action Potential

Answer 5

When a neuron is activated by a stimulus received at its dendritic terminal, it triggers an electrical change resulted from a change in the permeability of the membrane of the neuron. Na+ rushes INTO the neuron (Inside more +) K+ leaves the cell (inside more -) Then back to resting potential

Question 6

Depolarization

Answer 6

Inside of the cell is more positive

Question 7

Repolarization

Answer 7

Inside of the cell is more negative

Question 8

Excitatory

Answer 8

Act to stimulate the firing of the postsynaptic neuron. Leads to changes that generate an AP in the responding neuron (Glutamate)

Question 9

Inhibitory

Answer 9

Act to block the changes that cause an AP to be generated

GABA

Question 10

Achetylcholine Nicotinic Receptor is what type of channel?

Answer 10

Na+ ligand-gated channel

Question 11

Uniport Carrier System

Answer 11

(facilitated diffusion) carriers mediate transport of one type of molecules at a time
• Directionality of molecule movement driven by concentrationgradient
• Conformational shift opens the channel to the cell interior

Question 12

Symport Carrier System

Answer 12

co-transport) carriers bind two types of dissimilar molecules and transport them together across a membrane in the same direction
• Secondary active transport – two molecules obligatorily coupled; movement of one molecule (usually an ion) down its concentration gradient drives uphill (against the gradient)
transport of another molecule

Question 13

Antiport Carrier System

Answer 13

(co-transport) carriers transport two types of dissimilar molecules across a membrane in opposite directions
• Secondary active transport – movement of an ion down its
concentration gradient powers the uphill transport (against the gradient) of another molecule
• Na+ / Ca2+ antiporter

Question 14

Ion Channels

Answer 14

Move ions down the conc gradient
NO conformation change
Highly selective (distinguish b/ Na+ and K+)

Question 15

Pumps (Primary Active Transport/ ATP hydrolysis)

Answer 15

Transport ions and many different types of small molecules
• ATP-driven leading to conformational change
• Primary active transport against concentrationgradient

Question 16

P(phosphorylation)-Type ATPases (pump)

Answer 16

Composed of two  subunits and two  regulatory subunits
• Driven by ATP hydrolysis – forming a phosphorylated intermediate resulting in a conformational change
• Maintain the gradients of essential ions (Na+, K+, Ca2+, and H+) that are the basis for a variety of cellular functions such as signaling, energy storage and secondary transport

Question 17

Types of P-Type ATPases

Answer 17

Na+/K+ ATPase, Ca2+ ATPase (PMCA), Ca2+ ATPase (SERCA), and H+/K+ ATPase

Question 18

Na+/K+ ATPase Pump

Answer 18

Transports 3 Na+ out of the cell and 2 K+ into the cell for each ATP hydrolyzed

Question 19

F-Type ATPase Pump

Answer 19

Transport H+ ions only, no phosphorylated intermediate, Transport H+ down conc gradient by ATP synthesis(inner membrane of mitochondria)

Question 20

V-Type ATPase Pump

Answer 20

H+ ions only, down the conc gradient, driven by ATP hydrolysis (low pH in vacuoles and lysosomes)

Question 21

ABC transporters

Answer 21

Largest family of transporters, overexpressed in human cancer cells, ATP-gated Cl- Channels (found in epithelial cells) Genetic defect causes cystic fibrosis