Exam 1: Drug-Receptor Interactions

Question 1

What is the difference between orthosteric binding and allosteric binding?

Answer 1

Orhtosteric binding is when the drug binds to the receptor AT THE ACTIVE SITE while

Question 2

Does allosteric binding still elicit a response? If so, explain.

Answer 2

Allosteric binding might still give a response since it might be binding close to the active site or it might be needed to help increase the efficacy of drug binding orthosterically

Question 3

What is the difference between specific and non-specific binding?

Answer 3

Specific binding is when the drug binds to the receptor it is intended for and non-specific binding is when the drug binds somewhere; it doesn’t matter where it binds

Question 4

What is an example of non-specific binding?

Answer 4

Albumin; Albumin is in the blood and the most prevalent protein that balances osmolality in the blood

Question 5

Explain the concept behind this graph.

Answer 5

Specific binding essentially “caps out” at a specific point. The cell only has so many receptors that can be bound to and once the maximum is reached, the drug can no longer bind to any more receptors.

Non-specific binding does not have a maximum and you can continue giving more and more of the drug and there will always still be some binding

Question 6

T/F An agonist can have an effect greater or lesser than a native ligand

Answer 6

True

Question 7

What is a native ligand?

Answer 7

A compound that is already found in the body
Ex: Epi

Question 8

Is allosteric binding competitive or non-competitive?

Answer 8

Non-competitive; allosteric binding can be either activators or inhibitors

Question 9

The ____ drug we give the more _____ we see.

Answer 9

Greater; response

Question 10

What happens when you keep giving a drug past its saturation?

Answer 10

More toxic side effects will be seen

Question 11

What is EC50 and what is Kd?

Answer 11

EC50 = where we see 50% of the effect of the drug (this is drug dependent)
Kd = when 50% of the receptors are bound (changes depending on drug and if it binds tightly to receptor)

Question 12

What is Emax and Bmax?

Answer 12

Emax = where we see 100% of the effect of the drug
Bmax = when 100% of the receptors are bound

Question 13

When you have a low Kd you have a ____ affinity for the receptor? What does this mean?

Answer 13

When you have a low Kd, you have a HIGH affinity for the receptor; this means that the drug binds really well to the receptor

Question 14

Are Kd and EC50 equal to each other? Why or why not?

Answer 14

They are not equal to each other because one or two receptors might be bound while seeing 50% of the effect but there are still hundreds of receptors to bind before getting to the Kd.

Question 15

Fill in the missing information on this graph

Answer 15

Question 16

Fill in the missing information for this graph and be able to explain what is occurring

Answer 16

A+C - when an allosteric activator is present, it binds somewhere other than the active site and might open up the active site more to help bind the agonist more; when given together with an agonist, we see an even greater response
A+B - competitive inhibitors act as an antagonists; they bind to the same active site as the agonist and they compete against each other for binding; to see a response, you need to give more of the agonist drug; eventually you will see the exact same response by giving a high enough dose of the agonist drug
A+D - allosteric inhibitors act as antagonists BUT they bind OUTSIDE of the active site; they can’t be outcompeted so regardless of how much of the agonist you give, you won’t get the same response in the end

Question 17

T/F Agonists are NOT downstream inhibitors

Answer 17

False; Agonists ARE downstream inhibitors