Receptors Ch 5 & 8

Question 1

Structure of receptors

Answer 1

Globular proteins, mostly in the cell membrane. Contains a hydrophobic hollow or cleft on its surface that functions as binding site.

Question 2

Function of receptors

Answer 2

Receive messages from chemical messengers and transmit them into the cell

Question 3

2 Types of Chemical Messengers
Released from?
Lifespan?

Answer 3

Neurotransmitters: released from nerve endings that cross a synapse to bind to receptor. Short lived. Between individual cells.
Hormones: released from gland and bind to target cells throughout the body.

Question 4

Chemical Messenger definition and 6 specific ex.

Answer 4

Switch on receptors without undergoing a chemical reaction. Ex. acetylcholine, adrenaline, dopamine, serotonin, aminobutyric acid, glutamic acid.

Question 5

Signal Transduction

Answer 5

Domino effect resulting from induced fit when messenger binds via weak forces leading to chemical signal inside cell.

Question 6

Binding interaction strength

Answer 6

Strong enough to hold messenger for signal transduction to take place.
Weak enough to allow messenger to depart.

Question 7

Antagonist

Answer 7

Bind more strongly than messenger to binding site, but does not elicit response

Question 8

Agonist

Answer 8

Binds reversibly to binding site and elicits response. Similar in structure to natural messenger.

Question 9

Ion channel structure

Answer 9

Five glycoprotein subunits tranversing cell membrane with receptor integrated into alpha helix subunits making hydrophillic channel in center. Has open and closed conformation.

Question 10

Ion channel function

Answer 10

Allow specific ions to to cross cell membrane down concentration gradient, depolarizes nerve membranes

Question 11

Inhibitory vs. Excitatory ion channels with examples

Answer 11

Inhibitory: Chloride ions (ex. GABA)
Exhibitory: Potassium, Sodium, Calcium ions (ex. nicotinic)

Question 12

G-protein coupled receptor with example

Answer 12

7 pass transmembrane helix with ligand binding site on the extracellular side and G-protien binding site on intracellular side (ex.Rhodopsin)

Question 13

G-protein coupled receptor function

Answer 13

Binding of messenger leads to induce fit that causes G protein to bind and bind GTP (enzyme function), splitting into alpha and beta-gamma subunits.

Question 14

G-protein function with 2 examples

Answer 14

Alpha s subunit activates membrane bound enzyme (ex. adenylate cyclase, phospholipase C). Inactivated when GTP is hydrolyzed to GDP.

Question 15

Adenylate cyclase

Answer 15

Activated by alpha s subunit, converts ATP to cyclic AMP.

Question 16

Competitive reversible antagonist

Effect of increasing concentration of messenger?

Answer 16

Binds noncovalently but different induced fit occurs so receptor is not activated. Increasing concentration reverses antagonism.

Question 17

Non competitive irreversible antagonists

Effect of increasing concentration of messenger?

Answer 17

Binds covalently but different inducted fit occurs so receptor is not activated. Increasing concentration has no effect.

Question 18

Noncompetitive reversible allosteric antagonist

Effect of increasing concentration of messenger?

Answer 18

Binds noncovalently to allosteric site. Increasing concentration has no effect.

Question 19

Antagonists by proximity effect

Answer 19

Binds reversibly to neighboring binding site and overlaps with messenger binding site (Noncompetitive).

Question 20

Partial agonist

Answer 20

Binds to receptor but causes conformational change that is not ideal or is able to bind to receptor in two ways, acting as an agonist in one method and as an antagonistic in the other.

Question 21

Inverse agonist

Answer 21

Binds to receptor and shuts down constitutive activity.

Question 22

Super agonist

Answer 22

Binds to receptor and elicits more than full biological response.

Question 23

Desensitization/Sensitization

Answer 23

Desensitization: endocytosis of receptors or reduced receptor biosynthesis, phosphorylation of receptor.
Sensitization: increased receptor synthesis.

Question 24

Dependence

Answer 24

need to take drug to have normal response that can occur with both agonists and antagonists due to increase receptor synthesis (sensitization).

Question 25

Alpha s subunit

Answer 25

Stimulates adenylate cyclase

Question 26

Alpha i subunit

Answer 26

Inhibits adenylate cyclase and may activate potassium channel

Question 27

Alpha o subunit

Answer 27

Inhibit neuronal calcium ion channels

Question 28

Alpha q subunit

Answer 28

Activates phospholipase C

Question 29

Tolerance

Answer 29

Higher dosage of drug required to produce the same effect by increasing the number of receptors.

Question 30

Phospholipase C

Answer 30

Cleaves phosphatidylinositol diphosphate (PIP2) into diacylglycerol (DG) and inositol triphosphate (IP3).

Question 31

Diacylglycerol

Answer 31

Hydrophobic secondary messenger activate protein kinase C (PKC).

Question 32

Inositol triphosphate

Answer 32

Hydrophilic secondary messenger that opens calcium channels in the endoplasmic reticulum to activate calcium dependent protein kinases and calmodulin.