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

Accepted Answer

A sigmoid curve

Question 4

A mutation in hemoglobin that increases its affinity for oxygen would most likely result in which physiological effect?

Accepted Answer

Reduced oxygen delivery to tissues

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

It decreases hemoglobin's affinity for oxygen by stabilizing the tense (deoxy) conformation.

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 high content of glycine and proline?

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 subunits, 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

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

Question 13

What is the primary function of intermediate filaments such as keratin?

Accepted Answer

To provide mechanical strength to cells and tissues

Question 14

Which protein forms a coiled-coil structure and is a major component of hair and nails?

Accepted Answer

Keratin

Question 15

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

Accepted Answer

Kinesin

Question 16

How does ATP hydrolysis drive the movement of myosin along actin filaments?

Accepted Answer

ATP hydrolysis causes myosin to detach from actin and reattach further along the filament, resulting in movement.

Question 17

Which of the following is a consequence of thalassemia?

Accepted Answer

Reduced rate of synthesis of α or β globin chains

Question 18

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

Accepted Answer

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

Question 19

Which of the following best explains why hemoglobin is more efficient than myoglobin at delivering oxygen to tissues?

Accepted Answer

Hemoglobin exhibits cooperative binding, allowing it to release oxygen more readily in tissues.

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

Study Guide - Practice Questions