Identifying the oxidized reactant in cellular respiration: In the reaction C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy, which component is oxidized during the process?

Introduction / Context:
Cellular respiration transfers electrons from glucose to oxygen through a series of redox reactions, ultimately generating ATP. Correctly assigning which reactant is oxidized clarifies electron flow and energy capture mechanisms in biology.

Given Data / Assumptions:

• Chemical equation: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy.
• Oxidation is loss of electrons; reduction is gain of electrons.
• Products reflect the oxidation states after reaction.

Concept / Approach:
Glucose carbons begin in a reduced state. During respiration, carbon atoms are oxidized to CO2 (higher oxidation state), meaning glucose loses electrons (often via dehydrogenation steps transferring electrons to NAD+ and FAD). Oxygen is reduced to water (it gains electrons). Thus, glucose is the oxidized component among the reactants.

Step-by-Step Solution:
Track oxidation states: carbon in glucose → carbon in CO2 (increase in oxidation state). Recognize electron carriers (NAD+, FAD) capture electrons from glucose-derived intermediates. Note that oxygen acts as terminal electron acceptor, becoming reduced to water. Select glucose as the oxidized reactant.

Verification / Alternative check:
Overall electron balance shows electrons extracted from glucose intermediates flowing through the electron transport chain to reduce O2 to H2O, confirming roles.

Why Other Options Are Wrong:
O2 is reduced, not oxidized; CO2 and H2O are products in lower-energy, oxidized states; ATP is not a reactant here.

Common Pitfalls:
Equating oxygen presence with oxidation of oxygen; in respiration, oxygen is the oxidizing agent but itself is reduced.

Final Answer:
C6H12O6 (glucose).