Final answer:
A reduced electron carrier is oxidized when it loses electrons, which involves a decrease in potential energy. Electron carriers like NAD+ change between oxidized and reduced forms, transferring energy within a cell. Oxidation is paired with reduction in coordinated redox reactions, enabling efficient energy transfer.
Step-by-step explanation:
A reduced electron carrier becomes an oxidized electron carrier through the process of oxidation, where electrons are removed from the molecule, decreasing its potential energy. This occurs in the midst of redox reactions, which are fundamental to cellular energy production. The electron carriers like NAD+ and FAD play critical roles in shuttling electrons between biochemical pathways, changing in form between their oxidized states (NAD+, FAD) and their reduced states (NADH, FADH2) as they participate in various metabolic reactions.
Oxidation involves the loss of electrons, often represented by hydrogen atoms, from the reduced molecule. For example, when NADH loses two electrons and a hydrogen ion (H+), it becomes NAD+, which is the oxidized version of the molecule as depicted in Figure 7.2. These transformations allow a cell to harness energy in small, controlled bursts, enabling efficient biochemical processes.
Overall, the transition from a reduced to an oxidized state transfers the energy from the electron donor to the electron acceptor, thus maintaining the essential energy flow within a cell.