Signaling: Can You Hear Me Now?

Question 1

What makes receptors similar to enzymes?

Answer 1

Saturation kinetics; if there’s a high enough ligand concentration, the receptors can all become occupied

Question 2

What is receptor affinity?

Answer 2

relationship between concentration of ligand in solution and the number of receptors occupied

Question 3

What is high receptor affinity?

Answer 3

when almost all receptors are occupied at low ligand concentrations

Question 4

What is low receptor affinity?

Answer 4

when it takes a high concentration of ligand for most receptors to be occupied

Question 5

What is the dissociation constant (Kd)?

Answer 5

concentration of free ligand needed to produce a state at which half the receptors are occupied; quantitative value describing receptor affinity

Question 6

What is the range of values for Kd?

Answer 6

10^-7 - 10^-10 M

Question 7

What does a very low Kd mean?

Answer 7

the receptor has a high affinity for the ligand

Question 8

What does a very high Kd mean?

Answer 8

the receptor has a low affinity for the ligand

Question 9

What are agonists?

Answer 9

drugs that activate the receptor to which they bind

Question 10

What are antagonists?

Answer 10

compounds that can bind to receptors without triggering the changes that occur when the normal ligand binds; can inhibit the receptor by preventing the normal second messenger from binding and activating it

Question 11

What are the similarities and differences between an agonist and an antagonist?

Answer 11

Neither are the normal ligand to a receptor.
However, an agonist can still cause a change in the receptor as though it were the normal ligand. Antagonist bind without triggering the changes that occur with the normal ligand; can inhibit the receptor by preventing the natural second messenger from activating

Question 12

How do cells shut down signaling?

Answer 12

1. Can reduce amount of free ligand, reducing total amount of signal
2. Can reduce the sensitivity of the receptor or the amount of receptor in the cell

Question 13

How do neurons shut down signals?

Answer 13

They reduce the amount of neurotransmitter present at synapses via reuptake.