L1 - Ligand binding to receptors

Question 1

explain the key factors involved in ligand binding

Answer 1

Binding sites are key to ligand binding
- these have unique complementary 3D shapes with Ligands that allow for specified binding
- Chemical forces of attraction between aa in the binding site facilitate bonding to the ligand

Question 2

what are the relative roles of different chemical forces in ligand binding

Answer 2

The strength of a ligand binding is relative to the type, distance and number of bonds formed between the ligand and the binding site

CHEMICAL FORCES:
Type: Van der waals +, H-bonds ++, ioninc +++, covalent ++++ (rare)

Question 2

Role of receptors in Ligand binding

Answer 2

receptors recognise endogenous mediators and transduce intracellular signalling pathways that alter cell function

Question 3

What is affinity

Answer 3

Affinity is the tendency of a drug to bind to its target site and is dependent on the combined forces of attraction (3D shape and chemical forces)

Question 4

explain the influence of KA and [A] on
fractional receptor occupancy (y)

Answer 4

KA = measure of affinity at which 50% drug occupancy occurs at the receptor at equilibrium (constant value for a given drug and its target)
[A] = the concentration of a drug

KA measures the affinity for a drug to its target and influenced by to the concentration of a drug at equilibrium, the higher the drug concentration the teh lower the KA, and the higher the y value

Question 5

describe the relationship between K
A and drug affinity

Answer 5

KA and drug affinity have an inverse relationship. (as one goes up the other goes down)
KA is the conc at which 50% receptor occupancy occurs; the lower the KA, the higher the affinity and vice versa.

Question 6

explain the concept of selectivity

Answer 6

Selectivity is a concentration-dependent property of a drug that enables drugs to bind preferentially to one drug target over other drug targets.

Question 7

what is the relationship between selectivity and drug affinity and ligand concentration

Answer 7

Selectivity is lost as higher concentrations of the drug are given. This is because increases in drug concentration increase affinity for secondary or tertiary binding sites after primary receptor saturation.