Intoduction Lectures

Question 1

Ligand-receptor binding selectivity

Answer 1

Receptor binds to complementary ligands like the lock and key theory

Question 2

Difference between receptors and ligands

Answer 2

• receptors are the lock and ligands are the key that fit into the lock . Receptors receive signals from ligands

Question 3

Difference between exogenous and endogenous ligands ?

Answer 3

Endogenous =naturally occurring molecules within the body that bind to receptors
Exogenous =external substances such as drugs that can also bind these receptors

Question 4

Drug-receptor interactions

Answer 4

-most drugs binds to receptors reversibly
-when the drug(ligand) binds forms a ligand-binding complex and the ligand dissociates from the receptor unchanged

Question 5

Ligand concentration and cellular response graph sa

Answer 5

Response can be plotted against drug concentration and can be used to determine the maximum dosage of drug an use the information to determine the Ec50

EC50=half maximal effective concentration
-worked our by drawing a line at the reponse at 50%

Question 6

Why do we use log scale to plot the relationship between ligand concentration and cellular response

Answer 6

It’s clearer and easier to follow

Question 7

Affinity of a ligand

Answer 7

How tightly the receptor binds to the ligand

Question 8

Efficiency of a ligand

Answer 8

The ability of ligand bind to cause a response

Question 9

Radioligand binding

Answer 9

-allows quantification of ligand-receptor affinity
-A radioactive form of the agonist or antagonist ligand is allowed to bind to cells (or membranes prepared from cells)
-low [ligand] = low binding
- high ligand] = high binding

Question 10

Quantification of drug-receptor
interactions

Answer 10

-tells us about the affinity of the ligand for the receptor and provides information on the number of receptors present
-graph plotters allows us to work out Bmax and KD

Bmax = (maximum binding capacity – information about RECEPTOR NUMBER)

KD=
(Dissociation constant, a measure of ligand AFFINITY)
-50% of the bmax. draw a line from that

Question 11

Agonist ligands

Answer 11

• bind to receptor and cause a response
  -possess both affinity for the receptor and also the
  ability to cause receptor activation (intrinsic efficacy) to bring about a cell response

Question 12

Antagonist ligand

Answer 12

• binds to the receptor and does not cause a response.blocks the receptor
  -possess affinity for the receptor, but not the ability to cause receptor activation (i.e. they lack intrinsic efficacy) and therefore cannot bring about a cell response

Question 13

The presence of a fixed concentration of a competitive antagonist effect on graph

Answer 13

-causes a parallel, rightward shift in the concentration-response curve as a higher concentration of agonist is needed for binding

Question 14

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