Which of the following is true of metabolism in its entirety in all organisms?

• A. Metabolism only includes the breakdown of molecules to release energy.
• B. Metabolism occurs only in animal cells.
• C. Metabolism is limited to the synthesis of macromolecules.
• D. Metabolism consists of all the chemical reactions that occur within an organism.

Answer: (D)

Verified step by step guidance

1. Understand the term 'metabolism': Metabolism refers to all the chemical reactions that occur within an organism to maintain life. These reactions are divided into two main categories: catabolism (breakdown of molecules to release energy) and anabolism (synthesis of macromolecules and other compounds).
2. Evaluate the first option: 'Metabolism only includes the breakdown of molecules to release energy.' This statement is incorrect because metabolism includes both catabolic and anabolic processes, not just the breakdown of molecules.
3. Evaluate the second option: 'Metabolism occurs only in animal cells.' This statement is incorrect because metabolism occurs in all living organisms, including plants, fungi, bacteria, and other cells, not just animal cells.
4. Evaluate the third option: 'Metabolism is limited to the synthesis of macromolecules.' This statement is incorrect because metabolism is not limited to synthesis; it also includes the breakdown of molecules and other chemical reactions necessary for life.
5. Conclude with the correct answer: 'Metabolism consists of all the chemical reactions that occur within an organism.' This statement is correct because it encompasses the entirety of metabolic processes, including both catabolic and anabolic reactions, in all organisms.