Question

in cellular respiration, oxygen is reduced to ____________
carbon dioxide
water
question 4
the large black arrow represents:
free energy of the reaction
enzyme activity
activation energy

Explanation:

In cellular respiration, oxygen acts as the final electron acceptor. In the electron - transport chain, electrons are passed through a series of carriers, and oxygen combines with these electrons and protons (\(H^{+}\)) to form water (\(H_{2}O\)). The reaction is \(O_{2}+4e^{-}+4H^{+}\to2H_{2}O\). Carbon dioxide (\(CO_{2}\)) is produced from the oxidation of organic molecules (such as glucose) in earlier steps of cellular respiration (e.g., in the citric acid cycle).

For the second part, the activation energy is the minimum amount of energy required to start a chemical reaction. In a reaction - energy diagram, the activation energy is the height of the energy barrier between the reactants and the products. The free energy of the reaction is the difference in free energy between the reactants and the products (represented by the yellow arrow in the diagram). Enzyme activity is not directly represented by the height of the curve in a simple reaction - energy diagram like this.

Answer:

water; activation energy