Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

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Answer 1

Question

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.

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Answer 2

Question

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.

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Answer 3

Question

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.

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Answer 4

Question

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.

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Answer 5

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.

Answer 6

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.

Answer 7

Chapter 12, Problem 1E

Summary Introduction

Muscle fibers possess the ability to contract and relax. Sarcomeres are the fundamental units of these muscle fibers that contain myosin protein. Cross-bridges are found where the heads of myosin dimer molecules overlap forming a bridge between thick and thin filaments of myofibrils.

Answer 8

Expert Solution & Answer

Answer to Problem 1E

Correct answer:

The correct answer is option (c).

Answer 9

Expert Solution & Answer

Answer 10

Expert Solution & Answer

Answer 11

Explanation of Solution

Explanation/justification for the correct answer:

Contraction of muscle fibers is powered by ATP. Cross-bridge cycling is an important feature of consideration here. When myosin head attaches to actin cross-bridges are formed. The myosin continues to attach to ADP and inorganic phosphate (Pi) in a relaxed state. The release of Pi triggers pulling of actin and results in a power stroke of contraction. So, when the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it. So, the correct answer is option (c).

Explanation for the incorrect answer:

Option (a) states ‘bound to actin and in lower energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. So, this is an incorrect option.

Option (b) states ‘bound to actin and in higher energy form.’ Cross-bridges are formed when myosin attaches to actin in a high energy form. Cross-bridges are not directly bound to actin filaments. So, this is an incorrect answer.

Option (c) states ‘in high energy form with ATP bound to it.’ The high energy form of myosin is formed when it is attached to ADP and Pi, not ATP. Hence, this option is incorrect.

Option (d) states ‘in low energy form with nothing bound to it.’ Myosin filaments are bound to ADP and Pi in a high energy form when cross-bridges are formed in a relaxed state of muscle cells. So, this option is incorrect.

Answer 12

Conclusion

Among the given options, option (c) is the correct choice. When the muscle cell is relaxed and intracellular ATP levels are normal, a cross-bridge will remain in the high energy form with ADP and Pi bound to it.