Receptors And Channels

Question 1

Receptor

Answer 1

A protein or group of proteins, usually embedded in cell membrane, allows cell to collect info about its surroundings

Question 2

Ligand

Answer 2

A chemical messenger (can be small molecule or peptide) that induces a conformational change in the receptor

Question 3

Conformational change

Answer 3

Change in shape of a receptor that induces some downstream signal transduction

Question 4

2 main types of receptors

Answer 4

Ligand gated ion channels and G protein coupled receptors

Question 5

2 main types of membrane bound receptors

Answer 5

Ligand gated ion channels

G protein coupled receptors

Question 6

Cells that produce AP

Answer 6

Neurons, muscle cells, cardiac cells

Question 7

Action potential purpose

Answer 7

How 3 types of cells communicate w each other

Question 8

How APs are used to communicate

2 methods

Answer 8

APs propagate down axon of a neuron, jump from the end of one neuron to beginning of the next
Ligand gated and voltage gated ion channels

Question 9

4 steps in Saltatory AP propagation

Answer 9

1. AP occurred in initial segment, Na channel opening and in
2. Local current makes depolarization brings axolemma at next node to threshold
3. AP develops at node 2
4. Local current produces depolarization that brings the 3rd axolemma at node to threshold

Question 10

RMP

Answer 10

Inside of cell overall charge -70

Question 11

Excitatory

Answer 11

Inside of a cells charge approaches 0 mv. Generally by letting + ions into cell

Question 12

Inhibatory

Answer 12

Inside of cells charge becomes more neg, generally by letting neg ions (Cl especially) into cell

Question 13

Depolarization

Answer 13

Excitatory, + ions into cell

Question 14

Hyperpolarization

Answer 14

Inhibatory, - ions into cell

Question 15

Agonist

Answer 15

A ligand that binds to a receptor and activates it

Question 16

Antagonist

Answer 16

A ligand that binds to a receptor that prevents it from activation

Question 17

Orthosteric antagonist

Answer 17

Acts on the main binding site of a receptor

Question 18

Allosteric antagonist

Answer 18

Acts on accessory binding site of a receptor. Therefore agonist unable to go into main binding site.

Question 19

Pore blocker

Answer 19

Physically obstructs the whole channel (ion channels). Nothing can go up or down.

Question 20

Ligand gated ion channels

• transmission type
• composed of

Answer 20

Fast

Several subunits arranged around a central ion pore. Agonist binding opens pore.

Question 21

Ligand gated ion channels

2 major families

Answer 21

Cys loop receptors and ionotropic glutamate receptors

Question 22

Cys loop receptors 3 ex

Answer 22

Nicotinic acetylcholine receptor
Glycine receptor
5HT3 receptor

Question 23

Ionotropic glutamate receptors

3 ex

Answer 23

AMPA
NMDA
Kainate

Question 24

Cys loop receptors

Named for what

Answer 24

Loop formed by disulfide bond between 2 cysteines near the N terminus

Question 25

Cys loop receptors | Composed of what

Answer 25

5 subunits arranged around a central pore. 5 subunits: 2 alpha, beta, gamma, delta

Question 26

Excitatory cys loop receptors

Answer 26

Nicotinic acetylcholine | Serotonin

Question 27

Inhibatory cys loop receptors

Answer 27

Glycine and gaba a

Question 28

Ligand Gating | What allow things in

Answer 28

Agonist binding changes the conformation, moving the obstruction and allowing ions to flow through

Question 29

Ligand gating | What blocks things

Answer 29

2nd transmembrane domain of the a subunit generally obstructs the ion pore

Question 30

Drugs that work on ligand ion channels: cys loop

Answer 30

Nicotinic acetylcholine: nicotine, vareniciline (chantix) | Glutamate: NMDA receptors (ketamine), AMPA receptors (aniracetam- cognition enhancer)

Question 31

Ex of cys loop receptor: nicotinic acetylcholine - exists where - contain what

Answer 31

- NMJ and in the CNS - NMJ NAChR contain alpha, beta, delta, and gamma - neuronal only contain alpha and beta

Question 32

Ex of cys loop receptor: nicotinic acetylcholine - what kind of conduction, ions passed - composed of what - what they do in brain in response to smoking

Answer 32

- excitatory- na, k, some ca - 5 subunits - nAChRs upregulate in response to chronic smoking

Question 33

NAChR activation states

Answer 33

Can go interchangeably from closed, open, and desensitized | Longer ligand bound more of a chance of being desensitized

Question 34

Ionotropic glutamate ligand receptors - 3 types - what they are/pass what

Answer 34

AMPA, NMDA, and kainate | -excitatory: pass na and k ions. NMDA can also pass ca ions

Question 35

Ionotropic glutamate ligand receptors - composed of what - each subunit has what, NMDA in particular - all must be what

Answer 35

- 4 subunits. Each one has 4 transmembrane domains. 2nd TM domain forms ion pore - binding site- not all are for glutamate. - NMDA- 2 binding sites for glutamate, 2 for glycine - all 4 binding sites must be occupied for channel to open

Question 36

Long term potentiation

Answer 36

The more often a neuron fires, the stronger the synapse gets. Implicated in learning and memory

Question 37

At RMP, NMDA receptors are blocked by what. About this process

Answer 37

Mg ions. Mg block is voltage dependent. Depolarization of neuron relieves this block, allows NMDAR to open

Question 38

NMDARs pass what, process of leading to stronger synapse. What these are also known as

Answer 38

Ca, activates CAMKII, leads to AMPARs inserted into synapse. More ampars= stronger synapse. NMDARs= coincidence detectors

Question 39

G protein coupled receptors - rate of signaling - role w genome - target for what

Answer 39

- slower than ligand gated ion channels - 3% of our genome dedicated to GPCR coding - for more than 1/2 of current pharmaceuticals

Question 40

GPCR classes

Answer 40

A- adrenergic receptors, muscarinic acetylcholine receptors B- Parathyroid hormone receptor C- metabotropic glutamate receptors, GABAb receptors

Question 41

G protein activation

Answer 41

Alpha and beta gamma G proteins nearby. Alpha has GDP bound at rest. When receptor occupied by agonist recruits alpha, GTP replaces GDP. GTP causes alpha to go to target protein. GTP hydrolyzed back to GDP. Energy from this causes something to happen to target

Question 42

Ga subunits Gas Gai

Answer 42

S- activation of adenylyl cyclase and increase in cAMP | I- inhibition of adenylyl cyclase and decrease in cAMP

Question 43

Ga subunits | Gaq

Answer 43

Activation of phospholipase c, phosphoinositol hydrolysis, increase in IP3 and DAG, release of Ca from intracellular stores

Question 44

GPCR desensitization How it occurs Independent of what

Answer 44

- if a ligand bound to GPCR for long period B-arrestin binds to receptor, tags it for internalization. Contributes to drug tolerance. - GPCR B-arrestin complex can act as protein scaffold in the cell - independent of G protein signaling

Question 45

Cholera toxin mechanism

Answer 45

Cholera internalized by cell. Disrupts conversion of GTP to GDP. Inc level GTP leads to abn hi cAMP levels. Activates cl ion pumps, release more cl into interstitial lumen. Na, k, and hco3 ions follow, leading to more h20 held in intestine to balance osmolarity