OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is essential for the cardiac muscle cells to function properly?

1. High levels of carbon dioxide

2. ATP and a blood supply of nutrients and oxygen

3. Cold temperatures

4. Frequent rest periods

The correct answer is: ATP and a blood supply of nutrients and oxygen

The proper functioning of cardiac muscle cells is heavily dependent on a constant supply of ATP, as these cells require energy to contract and pump blood effectively throughout the body. ATP is generated through aerobic respiration, a process that significantly relies on oxygen and nutrients carried by the bloodstream. Therefore, a robust blood supply that includes both oxygen and essential nutrients is crucial for sustaining the metabolic needs of these cells. Having sufficient oxygen is vital because cardiac muscle cells are among the most metabolically active in the body, demanding high levels of energy to maintain their constant activity. Without adequate oxygenation and nutrients, cardiac cells would not be able to generate enough ATP, leading to impaired heart function and potentially severe health consequences. The other options do not align with the needs of cardiac muscle cells; high levels of carbon dioxide do not support cellular respiration but rather indicate inadequate oxygen supply. Cold temperatures can negatively affect muscle metabolism and circulation, while frequent rest periods do not meet the continuous energy demands of cardiac muscle, which must work relentlessly to maintain blood circulation.