Membrane-Bound Receptors

Question 1

What are receptors

Answer 1

a way in which cells can communicate with each other and gain information about the area around them

Question 2

2 types of receptors

Answer 2

ligand-gated ion channels and G protein coupled receptors

Question 3

What binds to the receptor

Answer 3

ligands, which are a chemical messenger

Question 4

What does a ligand do when it binds

Answer 4

induces a conformational change in the receptor tell the cell something about its environment. The receptor changes shape and tells downstream to do something.

Question 5

what cells produce Action Potentials

Answer 5

neurons, muscle cells, and cardiac cells

-how these cells communicate with each other

Question 6

How does the AP communicate and what starts in and keeps it going

Answer 6

the AP propagates down the axon of a neuron and jumps from the end of on neuron to the beginning of the next. -the ligand-gated ion channel starts the AP
-Voltage-gated ion channels propagate the signal

Question 7

Excitatory

Answer 7

the inside of the cells charge approaches 0mV getting less negative
-Depolarization

Question 8

Inhibitory

Answer 8

the inside of the cells charge becomes more negative, further away from creating an AP
-Hyperploarization

Question 9

Resting membrane potential

Answer 9

inside of the cell has an overall negative charge of -70mV

Question 10

Agonist

Answer 10

a ligand that binds to a receptor, thereby activating it

Question 11

Antagonist

Answer 11

a ligand that binds to a receptor that prevents it from activating

Question 12

Orthosteric Antagonist

Answer 12

Acts on the main binding site of the receptor, blocks the agonist from the binding site

Question 13

Allosteric antagonist

Answer 13

acts on an accessory binding site of the receptor

-changes the receptor shape so the agonist can’t bind, doesn’t fit

Question 14

Pore blocker

Answer 14

physically obstructs the channel

Question 15

Ligand-Gated Ion Channel

Answer 15

• fast transmission
• composed of several subunits arranged around a central ion pore
• agonist binding opens pore

Question 16

Ligand-Gated Ion channel families

Answer 16

• cys-loop receptors

- Ionotropic Glutamate Receptors

Question 17

Cys-loop receptor types

Answer 17

• nicotinic ACh receptor
• glycine receptor
• 5HT-3 receptor

Question 18

Ionotropic Glutamte receptor types

Answer 18

• AMPA receptor
• NMDA receptor
• Kainate receptor

Question 19

Cys-Loop receptors

Answer 19

• have a loop thats formed by a disulfide bond between two cysteine near the N-terminus
• Made of 5 subunits arranged around a central pore: alpha, beta, gamma, delta, epsilon

Question 20

cys-loop excitatory

Answer 20

Nicotinic-ACh

Serotonin

Question 21

Cys-loop inhibitory

Answer 21

Glycine and GABAa

Question 22

Gating

Answer 22

This is what causes the ion pore to be closed

• the second transmembrane of the alpha subunit is what forms the gate
• agonist binding changes the conformation, moving the obstruction (gate) allowing ions to flow through

Question 23

drugs that act on cys-loop receptors

Answer 23

• nicotinic-ACH: nicotine, Carenicline (chantix)

- Barbituates, benzos, alcohol, ambien

Question 24

drugs that act on Glutamate receptor

Answer 24

NMDA receptors: Ketamine

AMPA receptors: Aniracetam (cognition-enhancer)

Question 25

Nicotinic-ACH receptor

Answer 25

exist at the neuromuscular junction (NMJ) and in the CNS - composed of 5 subunits - NMJ nAChR contains alpha, beta, gamma, and delta - Neuronal nAChRs contain only alpha and Beta subunits - in the brain nAChRs upregulate in response to chronic nicotine like smoking

Question 26

nAChR excitatory

Answer 26

pass Na, K, and some Ca ions

Question 27

Iontropic Glutamate Receptors

Answer 27

- AMPA - NMDA - Kainate - composed of 4 subunits - -each subunit has 4 transmembrane domains and the 2nd transmembrane forms the ion pore - each subunit has a binding site-not all binding sites are for glutamate

Question 28

Iontropic Glutamate Receptors, excitatory

Answer 28

pass Na and K ions | NMDA receptors can also pass Ca ions

Question 29

NMDA receptor binding sites

Answer 29

2 binding sites for glutamate, 2 binding sites for glycine | -all 4 binding sites must be occupied for the channel to open.

Question 30

long term potentiation

Answer 30

the more often a neuron fires the stronger the synapse gets

Question 31

NMDA receptors at resting membrane, and what happens when activated

Answer 31

NMDAr are blocked by Mg - Mg is voltage dependent - depolarization of neuron relieves the block, allows NMDAr to open - When open Ca can pass which activates Ca calmodulin Kinase II - which leads to AMPARs being inserted into the synapse - more AMPARs=stronger synapse - NMDARs are "coincidence detectors"

Question 32

G-Protein-Coupled receptors (GPCR)

Answer 32

slower signaling that ligand-gated ion channels - relay on 2nd messenger - 3% of our genome dedicated to GPCR coding * *target for more than 1/2 of current drugs

Question 33

GPCR classes

Answer 33

A:adrenergic receptors, muscarinic acetylcholine receptors B:Parathyroid Hormone receptor C: metabotropic glutamate receptors, GABAB receptors

Question 34

G-Proteint activation

Answer 34

- ligand binds to receptor - GDP is traded for a GTP on the alpha subunit - Beta/gamma break off - Alpha and GTP activate target protein - activation is terminated when GTP is hydrolyzed to GDP

Question 35

G alpha S

Answer 35

activation of adenylyl cyclase and increase in cAMP

Question 36

G alpha I

Answer 36

inhibition of adenylyl cyclase and decrease in cAMP

Question 37

G alpha Q

Answer 37

activation of phospholipase C, phosphoinositol hydrolysis, increase in IP3 and DAG, and release of Ca2+ from intracellular stores

Question 38

Downstream targets of GPCR

Answer 38

- Target enzymes: Adenylate cyclase and phospholipase C - 2nd messengers: cAMP, IP3, DAG - Protein kinases: PKG, PKA, PKC - Effectors: enzymes, transport proteins, contractile proteins, Ion channels

Question 39

GPCR desensitization

Answer 39

if a ligand is bound onto a GPCR for a prolonged time it is phosphorated by a specific kinase - Beta-Arresting binds to the receptor, - causing it to loose its ability to associate with G-protein, which tags it for internalization - undergoes endocytosis which removes its receptor fro the membrane. - -this contributes to drug tolerance

Question 40

GPCR-beta arrestin

Answer 40

can act as a protein scaffold inside the cell. Contains the GPCR -this is independent of G protein signaling

Question 41

Cholera Toxin Mechanism

Answer 41

- cholera toxin is internalized by the cell - disrupts conversion of GTP to GDP (blocks GTPase activity preventing inactivation) - increases level of GTP leads to abnormally high cAMP levels - -this activates Cl ion pumps which release more Cl into the investing lumen - -Na, K and bicar ions follow--leading to more water being held in the intestine to balance osmolarity