Which molecule provides the energy for cells, including muscle contraction, produced via both anaerobic and aerobic pathways?

Which molecule provides the energy for cells, including muscle contraction, produced via both anaerobic and aerobic pathways?

• A. ATP
• B. ADP
• C. AMP
• D. NADH

Answer: (A)

ATP is the energy currency of cells, and it directly powers muscle contraction. When a muscle fiber contracts, the myosin head uses energy released from ATP hydrolysis (ATP → ADP + Pi) to perform the power stroke that pulls actin filaments. The body can generate ATP through both anaerobic pathways (like glycolysis without oxygen) and aerobic pathways (mitochondrial respiration with oxygen), so ATP is the immediate energy source in both conditions. ADP and AMP are the breakdown products of ATP and aren’t the direct energy used for contraction, while NADH is an electron carrier that helps drive ATP production but is not the work molecule itself.

ATP is the energy currency of cells, and it directly powers muscle contraction. When a muscle fiber contracts, the myosin head uses energy released from ATP hydrolysis (ATP → ADP + Pi) to perform the power stroke that pulls actin filaments. The body can generate ATP through both anaerobic pathways (like glycolysis without oxygen) and aerobic pathways (mitochondrial respiration with oxygen), so ATP is the immediate energy source in both conditions. ADP and AMP are the breakdown products of ATP and aren’t the direct energy used for contraction, while NADH is an electron carrier that helps drive ATP production but is not the work molecule itself.