Quiz on Protein Function and Binding

Which of the following best defines a ligand?

• A covalent bond between two proteins

• Any molecule that reversibly binds to a protein

• A protein that binds to DNA only

• A molecule that irreversibly modifies an enzyme

Binding affinity is typically expressed by which parameter?

• ΔG

• Kd (dissociation constant)

• Vmax

• Hill coefficient

If a protein has a Kd of 2 μM for a ligand, what fraction of binding sites are occupied at [L] = 2 μM?

• 0.25

• 0.50

• 0.75

• 1.00

Which interaction is **not** typically involved in protein-ligand binding?

• Hydrogen bonding

• Ionic interactions

• Hydrophobic effects

• Covalent disulfide bonds

In food science, binding of milk proteins (caseins) to tea polyphenols results in:

• Reduced bitterness and decreased antioxidant activity

• Increased antioxidant activity

• No effect on polyphenols

• Irreversible protein denaturation

Which statement best describes myoglobin (Mb)?

• It transports oxygen in the blood.

• It binds oxygen cooperatively.

• It stores oxygen in muscle tissue.

• It has four subunits like hemoglobin.

Hemoglobin (Hb) shows a sigmoidal oxygen-binding curve because:

• It binds oxygen irreversibly

• It contains only one heme group

• It is not affected by pH or CO₂

• It exhibits cooperative binding

Which pigment is responsible for the bright red color of fresh meat?

• Myoglobin

• Metmyoglobin

• Oxymyoglobin

• Hemoglobin

The brownish discoloration of stored meat is due to:

• Formation of oxymyoglobin

• Reduction of myoglobin

• Formation of metmyoglobin

• Denaturation of hemoglobin

In terms of nutrition, hemoglobin and myoglobin are important because they:

• Are sources of plant-based non-heme iron

• Contain heme iron, which has high bioavailability

• Prevent protein denaturation in meat

• Provide antioxidants