Choose the pair of terms that correctly completes this sentence: Catabolism is to anabolism as is to          . a. exergonic; spontaneous b. exergonic; endergonic c. free energy; entropy d. work; energy

Verified step by step guidance

1. Identify the key terms in the question: Catabolism and anabolism are metabolic pathways. Catabolism breaks down molecules, releasing energy, while anabolism builds up molecules, requiring energy input.
2. Understand the relationship between the terms: Catabolism is associated with the release of energy, which is an exergonic process. Anabolism, on the other hand, requires energy, which is an endergonic process.
3. Match the relationships: Since catabolism is to anabolism as one process is to its opposite, we need to find a pair that represents a similar relationship of opposites in terms of energy.
4. Review the options given: a) exergonic; spontaneous - both terms imply a release of energy, b) exergonic; endergonic - these terms are opposites, where exergonic releases energy and endergonic requires energy, c) free energy; entropy - these terms are related to different concepts, d) work; energy - these are not directly opposites in the context of metabolic pathways.
5. Select the correct answer based on the analysis: The correct answer is b) exergonic; endergonic, as these terms correctly represent the energy relationships in catabolism and anabolism respectively.

Key Concepts

Catabolism and Anabolism

Catabolism refers to the metabolic pathways that break down molecules into smaller units, releasing energy in the process. In contrast, anabolism involves the synthesis of complex molecules from simpler ones, requiring an input of energy. Together, these processes are essential for maintaining the energy balance and overall metabolism in living organisms.

Exergonic and Endergonic Reactions

Exergonic reactions are those that release energy, often associated with catabolic processes, while endergonic reactions require an input of energy, typical of anabolic processes. The distinction between these two types of reactions is crucial for understanding how energy flows within biological systems and how cells harness energy for growth and maintenance.

Free Energy

Free energy, often represented as Gibbs free energy, is a thermodynamic quantity that indicates the amount of energy available to do work in a system at constant temperature and pressure. It helps predict the direction of chemical reactions; reactions with a negative change in free energy are spontaneous, while those with a positive change are non-spontaneous and require energy input.