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.
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1
Understand the process of cellular respiration, which involves glycolysis, the citric acid cycle, and oxidative phosphorylation.
Recognize that oxygen (O2) plays a crucial role in the electron transport chain, which is part of oxidative phosphorylation.
Recall that in the electron transport chain, oxygen acts as the final electron acceptor.
Know that when oxygen accepts electrons, it combines with protons (H+) to form water (H2O).
Conclude that the labeled oxygen would first appear in water (H2O) as it is the product of oxygen accepting electrons at the end of the electron transport chain.
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Key Concepts
Here are the essential concepts you must grasp in order to answer the question correctly.
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.
Isotope labeling is a technique used in biochemistry to track the movement of atoms through metabolic pathways. By using isotopes, such as oxygen-18, researchers can trace how labeled molecules are incorporated into different compounds during cellular processes, providing insights into metabolic pathways and reactions.
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 these products. Understanding which product is formed first from labeled oxygen helps elucidate the sequence of reactions in cellular respiration.