Question 1

Which of the following statements best describes the role of ATP hydrolysis in muscle contraction?

Accepted Answer

ATP hydrolysis causes the myosin head to detach from actin, resetting the contraction cycle.

Question 2

What is the primary structural difference between thick and thin filaments in muscle fibers?

Accepted Answer

Thick filaments are composed mainly of myosin, while thin filaments are composed mainly of actin.

Question 3

Which protein acts as a molecular spring, linking thick filaments to the Z-disk in muscle fibers?

Accepted Answer

Titin

Question 4

During the sliding filament model of muscle contraction, which event directly follows the release of inorganic phosphate ($P_i$) from the myosin head?

Accepted Answer

The myosin head performs the power stroke, moving the actin filament.

Question 5

Which of the following best explains why myoglobin is effective for oxygen storage but not for oxygen transport in mammals?

Accepted Answer

Myoglobin has a high affinity for oxygen, so it binds oxygen tightly and only releases it at very low $pO_2$.

Question 6

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

Accepted Answer

Sigmoidal

Question 7

What is the function of the troponin-tropomyosin complex in muscle contraction?

Accepted Answer

It blocks myosin binding sites on actin until calcium ions bind to troponin.

Question 8

Which of the following correctly describes the role of calcium ions ($Ca^{2+}$) in muscle contraction?

Accepted Answer

$Ca^{2+}$ binds to troponin, causing a conformational change that exposes myosin binding sites on actin.

Question 9

Which of the following is TRUE regarding the heme group in myoglobin?

Accepted Answer

The heme group allows reversible binding of $O_2$ via Fe(II) without undesired redox reactions.

Question 10

A patient is exposed to carbon monoxide ($CO$). Which of the following best explains why $CO$ poisoning is dangerous in terms of myoglobin and hemoglobin function?

Accepted Answer

$CO$ binds to the heme group with higher affinity than $O_2$, preventing oxygen binding and delivery.

Question 11

Which of the following equations correctly represents the hydrolysis of ATP during muscle contraction?

Accepted Answer

$ATP \rightarrow ADP + P_i$

Question 12

Which protein is responsible for the regulatory control of muscle contraction by binding calcium ions?

Accepted Answer

Troponin

Question 13

Which of the following best describes the conformational change in myosin during muscle contraction?

Accepted Answer

The myosin head rotates after hydrolyzing ATP, allowing it to bind to a new position on actin.

Question 14

Which of the following statements about oxygen binding to myoglobin is correct?

Accepted Answer

Myoglobin binds oxygen non-cooperatively, resulting in a hyperbolic binding curve.

Question 15

Which of the following is a consequence of cooking meat to temperatures above 150°F (66°C)?

Accepted Answer

Actin and myosin become very firm, shorten in length, and squeeze out more water, making the meat tough and dry.

Question 16

Which of the following best explains the color change in meat when exposed to air after cutting?

Accepted Answer

Oxymyoglobin is converted to metmyoglobin, turning the meat brown.

Question 17

Which of the following is TRUE regarding the oxygen affinity of hemoglobin compared to myoglobin?

Accepted Answer

Hemoglobin has a lower oxygen affinity than myoglobin at low $pO_2$, allowing it to release oxygen more readily in tissues.

Question 18

Which of the following best describes the quaternary structure of hemoglobin?

Accepted Answer

Hemoglobin is a tetramer composed of two alpha and two beta chains.

Question 19

Which of the following is a key difference between the oxygen binding properties of hemoglobin and myoglobin?

Accepted Answer

Hemoglobin exhibits cooperative binding, while myoglobin does not.

Muscle Contraction and Oxygen Binding by Myoglobin and Hemoglobin

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