Membrane Bound Receptors

Question 0

The chemical messengers that bind to receptors?

Answer 0

Ligands

Question 1

Way in which cells can communicate with each other, gain information about the area around them?

Answer 1

Receptors

Question 2

A ___ binding to a receptor will induce a conformational change in the receptor, telling the cell something about it’s environment.

Answer 2

Ligand

Question 3

2 Main Types of Receptors?

Answer 3

Ligand-gated ion channels

G protein-coupled receptors

Question 4

___, ___ & ___ all produce action potentials. This is how these types of cells communicate with each other.

Answer 4

Neurons
muscle cells
cardiac cells

Question 5

In order to communicate, APs need to propagate down the ___ of a neuron, and “jump” from the end of one neuron to the beginning of the next.

           * Ligand-gated ion channels
           * Voltage-gated ion channels

Answer 5

axon

Question 6

Resting membrane potential: Inside of the cell has an overall negative charge of ___.

• ___ = means that the inside of the cell’s charge approaches 0 mV (more + inside).
• ___ = means that the inside of the cell’s charge becomes more negative (more - inside….this is also known as?).

Answer 6

~-70mV

• Excitatory
• Inhibitory
• hyperpolarization

Question 7

A ligand that binds to a receptor, thereby activating it is called an?

Answer 7

Agonist

Question 8

A ligand that binds to a receptor that prevents it from activating is called an?

Answer 8

Antagonist

Question 9

Acts on the main binding site of the receptor?

• Nothing else can bind. Directly blocking where agonist could bind.
• Competitive.

Answer 9

Orthosteric antagonist

Question 10

Acts on an accessory binding site of the receptor?
*Creates a conformational change so the agonist can not bind. “Breaking the lock.”
Non-competitive.

Answer 10

Allosteric antagonist

Question 11

Physically obstructs the channel (ion channels)?

*Non-competitive.

Answer 11

Pore Blocker

Question 12

Fast transmission.
Composed of several subunits arranged around a central ion pore.
*___ binding opens pore.

Answer 12

Ligand-gated ion channels

*Agonist

Question 13

Ligand-Gated Ion channels - Major Families:

1) ___ = nicotinic acetylcholine receptor, glycine receptors, 5HT-3 receptor, etc. (pentamer)
2) ___ = AMPA receptor, NMDA receptor, kainate receptor. (tetramer)

Answer 13

1) Cys-loop receptors

2) Ionotropic Glutamate receptors

Question 14

Cys-Loop Receptors:

1) Named for the loop formed btw the ___ bond btw 2 cysteines near the ___.
2) Made up of 5 subunits (pentamer) arranged around a ___.
* alpha, beta, delta, gamma, epsilon
3) Name 2 examples of EXCITATORY Cys-loop receptors?
4) Name 2 examples of INHIBITORY Cys-loop receptors?

Answer 14

1) disulfide 
N-terminus
2) central pore
3) Nicotinic acetylcholine receptors
Serotonin receptors
4) Glycine
GABAa

Question 15

Cys-Loop Receptors - Gating:

• The second transmembrane domain of the ___ subunit generally obstructs the ion pore.
• ___ binding changes the conformation, moving the obstruction and allowing the ions to flow through.

Answer 15

1) alpha subunit

2) Agonist binding

Question 16

Drugs that act on Ligand-Gated Ion channels:
*Cys-loop receptors:
~Nicotinic acetylcholine receptors: 2 examples??
~___, ___, ___
*Glutamate receptors:
~NMDA receptors: ?
~AMPA receptors: ? (cognition enhancer)

Answer 16

~Nicotine
~Vareniclin (Chantix) 
~Barbiturates, Benzodiazepines, alcohol
~Ketamine
~Aniracetam

Question 17

Cys-loop receptor example: Nicotinic Acetylcholine receptor

1) Exist at the ___ and in the ___.
2) ___ contain alpha, beta, gamma & delta subunits.
3) ___ contain only alpha and beta subunits.

Answer 17

1) Neuromuscular junction (NMJ), CNS
2) NMJ nicotinic acetylcholine receptors
3) Neuronal nicotinic acetylcholine receptors

Question 18

Cys-loop receptor example: Nicotinic Acetylcholine receptor:

1) Excitatory = pass which 3 ions. (Different kinds of nACHR pass different amounts of calcium through them)
2) Composed of ?
3) In the brain, nACHRs upregulate in response to ?

Answer 18

1) sodium, potassium, some calcium ions
2) 5 subunits
3) Chronic nicotine

Question 19

nACHR Activation States: 3 states???

*___ = ligand is bound but the channel is still closed, kind of independent of ligand binding.

Answer 19

Opened, closed, desensitized

*Desensitized

Question 20

Many downstream targets of ____ = Enzymes, transport proteins, contractile proteins, ion channels.

Answer 20

G protein coupled receptors

Question 22

Ionotropic Glutamate Receptors:
3 Examples?
1) Excitatory - Pass which 2 ions? These receptors can also pass calcium ions?
2) Composed of ?

Answer 22

AMPA receptors 
NMDA receptors 
Kainate receptors
1) sodium & potassium 
    NMDA
2) 4 subunits

Question 23

Ionotropic Glutamate Receptors:

1) Composed of 4 subunits, each subunit has 4 transmembrane domains, ___ forms the ion pore.
2) Each subunit has a ___, not all of these are for ___.

Answer 23

1) second transmembrane domain
2) Binding site
Glutamate

Question 24

Ionotropic Glutamate Receptors: Binding Sites

1) ___ = 2 binding sites for glutamate, 2 binding sites for glycine
2) All ___ binding sites must be occupied for the ___.

Answer 24

1) NMDA receptor
2) 4
channel to open

Question 25

The more often a neuron fires the “stronger” the synapse gets?
*Implicated in learning & memory

Answer 25

Long Term Potentiation (LTP)

Question 26

LTP:
At resting membrane potential, NMDA receptors are blocked by ___.
*___ is voltage dependent
*___ relieves the block, allows NMDAR to open

Answer 26

Magnesium

• Magnesium block
• Depolarization of neuron

Question 27

LTP:
NMDARs pass ___, which activates ___, which leads to AMPARs inserted into the ___.
*More ___ = stronger synapse
NMDARs are “___ ___” (they can detect when a neuron fires over and over again)

Answer 27

• calcium
• Calmodulin kinase II (CaMKII)
• synapse
• AMPARs
• “coincidence detectors”

Question 28

G-Protein Coupled Receptors:

1) Slower signaling than ?
2) Rely on ___ for signaling.
3) ~3% of our genome dedicated to ___.
4) Target for more than half of ___.

Answer 28

1) Ligand-gated ion channels
2) Second messengers
3) GPCR coding
4) current pharmaceuticals

Question 29

G-Protein Coupled Receptors = Three Main Classes:

1) Class A: ??
2) Class B: ?
3) Class C: ??

Answer 29

1) Adrenergic receptors
Muscarinic acetylcholine receptors
2) Parathyroid hormone receptor
3) Metabotropic glutamate receptors, GABAb receptors

Question 30

Effects of signaling tend to be more long term than Ligand-gated ion channels?

Answer 30

G-Protein Coupled Receptors

Question 31

G alpha Subunits:

Activation of adenylyl cyclase and increase in ___.

Answer 31

G alpha S

-cAMP

Question 32

G alpha Subunits:

Inhibition of adenylyl cyclase and decrease in ___.

Answer 32

G alpha I

-cAMP

Question 33

GPCR Desensitization:

1) If a ___ is bound onto a GPCR for a prolonged period of time, ___ binds to the receptor, thus tagging it for ___.
* This contributes to ?
2) The ___ can act as a protein scaffold inside the cell.
3) Independent of ?

Answer 33

1) Ligand
B-arrestin 
Internalization 
*Drug tolerance 
2) GPCR-B-arrestin complex 
3) G protein signaling

Question 34

Cholera Toxin Mechanism:
1) ___ is internalized by the cell.
2) Disrupts conversion of ___ to ___.
3) Increased level of ___ leads to abnormally high ___ levels.
*Activates ___ pumps, which release more chloride into the ___.
*___, ___ & ___ ions follow, then leading to more water being held in
the intestine to balance osmolarity.

Answer 34

1) Cholera toxin
2) GTP to GDP
3) GTP
cAMP
*chloride ion
intestinal lumen
*Sodium
potassium
bicarb

Question 35

G alpha Subunits:
Activation of phospholipase C, phosphoinositol hydrolysis, increase in ___ & ___ and release of ___ from intracellular stores.

Answer 35

G alpha q
IP3 & DAG
calcium