Question 1

Which of the following statements best describes the difference between native PAGE and SDS-PAGE in protein analysis?

Accepted Answer

Native PAGE preserves protein structure and separates based on shape and charge, while SDS-PAGE denatures proteins and separates based on molecular weight.

Question 2

Which type of interaction is primarily responsible for stabilizing the tertiary structure of a protein?

Accepted Answer

Hydrogen bonds, salt bridges, and hydrophobic interactions

Question 3

A researcher wants to determine if a specific protein contains disulfide bonds. Which electrophoresis condition should they use?

Accepted Answer

Reducing SDS-PAGE

Question 4

Which of the following best explains why SDS is used in SDS-PAGE?

Accepted Answer

SDS coats proteins with a negative charge, allowing separation based on molecular weight.

Question 5

Which blotting technique would you use to detect a specific RNA sequence in a sample?

Accepted Answer

Northern blot

Question 6

Hemoglobin exhibits cooperative binding of oxygen. Which shape best describes its oxygen binding curve?

Accepted Answer

Sigmoidal

Question 7

What is the effect of 2,3-bisphosphoglycerate (BPG) on hemoglobin's oxygen affinity?

Accepted Answer

BPG decreases hemoglobin's affinity for oxygen by stabilizing the T state.

Question 8

Which of the following is a positive homotropic allosteric effector of hemoglobin?

Accepted Answer

Oxygen ($$O_2)$$

Question 9

The Bohr effect describes how changes in pH affect hemoglobin's oxygen binding. What happens to hemoglobin's oxygen affinity as pH decreases?

Accepted Answer

Oxygen affinity decreases, favoring the T state.

Question 10

Which equation correctly represents the equilibrium constant for myoglobin binding to oxygen?

Accepted Answer

$$K = \frac{[Mb][O_2$]}{[$$MbO_2$$]}$$

Question 11

A patient with sickle-cell disease has a mutation in the hemoglobin gene. What is the primary consequence of this mutation at the molecular level?

Accepted Answer

Hemoglobin forms abnormal aggregates that distort red blood cells.

Question 12

Which of the following statements about myoglobin and hemoglobin is correct?

Accepted Answer

Myoglobin is a monomeric protein, while hemoglobin is a tetrameric protein.

Question 13

Which amino acid residue in hemoglobin is directly involved in the conformational change upon oxygen binding?

Accepted Answer

Proximal histidine (His F8)

Question 14

What is the main reason fetal hemoglobin has a higher affinity for oxygen than adult hemoglobin?

Accepted Answer

Fetal hemoglobin has a mutation at Ser 143 that reduces BPG binding.

Question 15

Which of the following is NOT a weak interaction that drives protein-protein interactions?

Accepted Answer

Covalent peptide bonds

Question 16

A mutation in the proximal histidine (His F8) of hemoglobin (H93G) decouples the F helix from the heme group. What is the effect on oxygen affinity?

Accepted Answer

Oxygen affinity increases because the heme group is less constrained.

Question 17

Which of the following best describes the role of allosteric effectors in hemoglobin function?

Accepted Answer

Allosteric effectors bind at sites other than the active site and modulate hemoglobin's oxygen affinity.

Question 18

Which of the following is a correct statement about the T and R states of hemoglobin?

Accepted Answer

The R state is stabilized by oxygen binding and has higher oxygen affinity.

Question 19

Which of the following equations correctly describes the fractional saturation ($$Y) of $$myoglobin with oxygen?

Accepted Answer

$$Y = \frac{[$$MbO_2$$]}{[Mb] + [$$MbO_2$$]}$$

Protein Function and Evolution: Structure, Analysis, and Hemoglobin Allostery

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