A biochemist wanted to study how various substances were used in cellular respiration. In one experiment, she allowed a mouse to breathe air containing O2 'labeled' by a particular isotope. In the mouse, the labeled oxygen first showed up in a. ATP. b. NADH. c. CO2. d. H2O.

Verified step by step guidance

1. Understand the concept of cellular respiration: Cellular respiration is a metabolic process in cells where oxygen is used to break down glucose, producing carbon dioxide, water, and energy (ATP).
2. Recognize the role of oxygen in cellular respiration: Oxygen is the final electron acceptor in the electron transport chain, a crucial step in cellular respiration. It combines with electrons and protons to form water.
3. Identify where labeled oxygen would appear: Since oxygen is used to form water in the electron transport chain, any isotopic label on the oxygen would first be detectable in the water produced.
4. Review the options given: The options are ATP, NADH, CO2, and H2O. Based on the role of oxygen in cellular respiration, determine which molecule would first incorporate the labeled oxygen.
5. Conclude the correct answer: The labeled oxygen would first show up in the molecule where oxygen directly participates in its formation during cellular respiration.

Key Concepts

Cellular Respiration

Cellular respiration is a metabolic process that converts biochemical energy from nutrients into adenosine triphosphate (ATP), and releases waste products. It involves several stages, including glycolysis, the citric acid cycle, and oxidative phosphorylation, where oxygen plays a crucial role as the final electron acceptor in the electron transport chain.

Isotopes in Biological Research

Isotopes are variants of a particular chemical element that have the same number of protons but different numbers of neutrons. In biological research, isotopes can be used as tracers to study metabolic pathways, as they allow scientists to track the movement and transformation of specific atoms within biological systems, such as oxygen in cellular respiration.

Products of Cellular Respiration

The main products of cellular respiration include ATP, carbon dioxide (CO2), and water (H2O). During the process, glucose is oxidized, and oxygen is reduced, leading to the formation of CO2 and H2O as byproducts. Understanding these products is essential for determining how labeled oxygen from the experiment would be incorporated into the mouse's metabolic processes.