Medical Biochemistry Lecture 5

Question 1

In what ways can protein act?

Answer 1

1) Biological catalysis (chymotrypsin, lysozyme)
2)Transport of ions and molecules(hemoglobin)
3)Storage of ions and molecules(myoglobin, ferritin)
4)Structure, movement(actin, myosin)
5)Transmitting messages(insulin)
6) Defense against pathogens(antibodies, cytokines)

Question 2

What are the characteristics of ligand binding?

Answer 2

-ligands and binding -sites require specificity
Regulated and often reversible, follow the rules of chemistry and go towards equilibrium
-ligand binding is often coupling to conformational changes , sometimes quite dramatic(induced fit)
-In multisubunit proteins, conformational changes in one subunit can affect the others (sooperativity)

Question 3

To create strong binding

Answer 3

Kd must less than 10 nano molar

Question 4

to create weak binding

Answer 4

Kd must be higher than 10 micromolar

Question 5

Proteins typically have high specificity

Answer 5

only certain ligands due to the complementary of the binding site and ligand

Question 6

what is the lock and key model?

Answer 6

assumes that complementary surfaces are pre-formed, complementary in size, shape, charge, hydrophilic/hydrophobic character

Question 7

What is the induced fit model?

Answer 7

conformational changes may occur upon ligand binding in either the protein or ligand or both

Question 8

What does induced fit allow?

Answer 8

Allows for tighter binding of the ligand, higher affinity for different ligands; also allows enzymes to stabilize the transition state