Question 1

Which statement best describes the role of the heme group in myoglobin and hemoglobin?

Accepted Answer

It is a porphyrin that chelates iron, enabling reversible oxygen binding.

Question 2

What is the equation for the fractional saturation (Y) of myoglobin with oxygen?

Accepted Answer

$$Y = \frac{pO_2$}{K + pO_2$}$$

Question 3

Hemoglobin exhibits cooperative binding of oxygen. Which curve best represents this behavior?

Accepted Answer

A sigmoid curve

Question 4

A patient has a mutation in hemoglobin that increases its affinity for oxygen. What is a likely physiological consequence?

Accepted Answer

Reduced oxygen release in tissues, leading to tissue hypoxia

Question 5

Which of the following best explains the Bohr effect in hemoglobin?

Accepted Answer

As pH increases, hemoglobin's affinity for oxygen increases.

Question 6

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

Accepted Answer

BPG decreases hemoglobin's affinity for oxygen by stabilizing the deoxy form.

Question 7

Which amino acid substitution is responsible for sickle cell hemoglobin (Hb S)?

Accepted Answer

Glu to Val

Question 8

Why do carriers of the sickle cell allele have a selective advantage in malaria-endemic regions?

Accepted Answer

Their red blood cells are less likely to be infected by Plasmodium falciparum.

Question 9

Which structural protein is characterized by a triple helix and a repeating Gly-X-Y sequence?

Accepted Answer

Collagen

Question 10

What is the main difference between the assembly of actin filaments and microtubules?

Accepted Answer

Actin filaments are assembled from globular actin, while microtubules are assembled from tubulin dimers.

Question 11

Which process describes the dynamic behavior of actin filaments where the rate of addition at one end matches the rate of removal at the other end?

Accepted Answer

Treadmilling

Question 12

Which statement best describes the structure of microtubules?

Accepted Answer

Microtubules are hollow tubes composed of 13 protofilaments made from tubulin dimers.

Question 13

Which motor protein moves processively along microtubules, transporting cargo toward the (+) end?

Accepted Answer

Kinesin

Question 14

What is the role of ATP hydrolysis in the function of myosin?

Accepted Answer

ATP hydrolysis drives the conformational change that moves myosin along actin filaments.

Question 15

Which of the following is a consequence of thalassemia?

Accepted Answer

Reduced rate of synthesis of α or β globin chains

Question 16

Which protein structure level is described by the arrangement of multiple polypeptide chains?

Accepted Answer

Quaternary structure

Question 17

Which of the following best explains why collagen fibers are strong and resistant to stretching?

Accepted Answer

Collagen fibers are covalently cross-linked after polypeptide synthesis.

Question 18

Which of the following is true about the evolutionary relationship between myoglobin and hemoglobin?

Accepted Answer

They share a common evolutionary origin and diverged after gene duplication.

Question 19

Which residue in the heme group of myoglobin forms a hydrogen bond to bound O$$_2$$?

Accepted Answer

His E7

Question 20

Which of the following is NOT a function of structural proteins?

Accepted Answer

Transporting oxygen in the blood

Protein Structure and Function: Myoglobin, Hemoglobin, Structural Proteins, and Motor Proteins

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