Signal Transduction

Question 1

What is an agonist

Answer 1

Drug that binds to receptor and initiate specific reaction that results to biological response

Question 2

Another name for second messengers

Answer 2

Effector molecules

Question 3

What affects the magnitude of cellular response?

Answer 3

Number of drug receptor complex
They form a direct proportion

Question 4

Give an example of drug that doesn’t act on receptor

Answer 4

Antacid: dissolves in stomach acid reducing stomach upset

Question 5

The two receptor states are

Answer 5

Active and inactive states

Question 6

How does agonist binding affect equilibrium between receptor states

Answer 6

It shifts the equilibrium from the inactive to active state to produce biologic effect

Question 7

How does antagonist affect equilibrium of receptor states

Answer 7

It has no effect on the equilibrium.

It stabilizes the inactive state

Question 8

Partial agonists effect on receptor state

Answer 8

It doesn’t completely shift the equilibrium to the active state.

A minimum percent of active state is gotten compared to the full agonist

Question 9

What is a receptor

Answer 9

It is a biological molecule to which drug binds and produce measurable response.

Question 10

Receptors could be;

Answer 10

Enzymes,
Structural proteins,
Nucleic acids

Question 11

The richest source of receptors are

Answer 11

Transembranous proteins.

They transduce extracellular signals into intracellular responses.

Question 12

List the four families of receptors

Answer 12

Ligand gated
Enzyme-linked receptors
Intracellular receptors
G- protein coupled receptor.

Question 13

Where does hydrophobic and hydrophilic ligands interact with receptors

Answer 13

Receptors within the cell -hydrophobic
Receptors on the membrane -hydrophilic

Question 14

Ligand gated Chanel activation

Answer 14

1) agonist binds on domain site.
2) open up the ion channel for influx of specific ion.
3) Fxn of the receptor differ in type of ions that are influxed

Question 15

Two main function of ligand gated receptor

Answer 15

Neurotransmission and Muscle Contraction.

Neurotransmission: ACH activates nicotinic receptor.
> There’s influx of Na+ or K+ changing ionic concentration across membrane (A.P)
In neurons.

> Contraction in muscles

Question 16

Effect of agonist on GABA receptor

Answer 16

Stimulates chloride influx leading to hyperpolarization of neurons.

This decrease Action potential generation.

Question 17

How does local Anesthesia agonist work

Answer 17

They bind to voltage gated sodium channels, inhibiting sodium influx and decreasing neuronal conduction.

Question 18

G protein receptor are in three forms

Answer 18

Gq , Gs and Gi

Question 19

Configuration of G-protein subunit;

Answer 19

Alpha subunit binds to GTP/GDP

Beta and gamma subunit anchors the g protein to the cell membrane

Question 20

Ligand gated ion channels open in how many seconds

Answer 20

Milliseconds

Question 21

Responses from G-protein coupled receptor last for how long?

Answer 21

It lasts from several seconds to minutes

Question 22

Second messengers are also known as what?

Answer 22

Activated effectors

Question 23

Types of g proteins and effectors they activate or inhibit

Answer 23

Gs- activates Adenylyl cyclase
Gi- inhibits Adenylyl cyclase.
Gq- activates phospholipase C

Question 24

How does enzyme linked receptor work

Answer 24

Using insulin receptor as case study;

Insulin receptor has tyrosine kinase at the Beta intracellular end.

When insulin binds;
>Tyrosine kinase autophosphorylate to get activated
>activated Tyrosine kinase activates insuline receptor substrates.
>Multissignalling pathway are activated.
> Insulin receptor substrates Futher phosphorylates other protein kinasesz phosphatases.
> This leads to biological effects of insulin

Question 25

What is the most important feature of intracellular ligands

Answer 25

They must be lipophilic to interact with intracellular receptors.

Question 26

What is the primary target of activation in intracellular receptors ?

Answer 26

The transcription factors in the cell nucleus that regulate gene expression

Question 27

Duration of response of enzyme linked receptors?

Answer 27

takes minutes to hours to act

Question 28

Response of intracellular receptors lasts for:

Answer 28

Hours to days

Question 29

Other targets of intracellular receptors are;

Answer 29

Structural proteins
Enzymes
RNA
Ribosomes

Question 30

What is the target of antimicrobials( trimethoprim)

Answer 30

Dihydrofolate reductase in the nucleus.

Question 31

What is the target of antineoplastic agents like paclitaxel

Answer 31

Tubulin

Question 32

What is the target of macrolide antibiotics like erythromycin

Answer 32

50s subunit of bacteria chromosomes

Question 33

Signal amplification is seen in which receptors?

Answer 33

Enzyme linked and G protein receptors

Question 34

Signal transduction has two important features;

Answer 34

Ability to amplify response.
Ability to prevent over stimulation of the cell

Question 35

How does the signal transduction prevent excessive stimulation

Answer 35

1: desensitizing receptors: this is as a result of phosphorylation of the receptors due to continuous Adminstration of agonist and antagonist.

2) Downregulation of receptors: in high dose concentration of agonist receptors are internalised.

3) refractory period; unresponsive receptors in ion channels.

Question 36

What’s the effect of antagonist on upregulation

Answer 36

Repeated exposure of antagonist leads to upregulation of receptors.

It makes receptors more sensitive to agonist and resistant to effects of antagonist in case of reversals of antagonist effect.