Which process does NOT require energy in RBCs?

Oxygen transport in red blood cells (RBCs) occurs through a passive diffusion process driven by the concentration gradient of oxygen between the alveoli in the lungs and the tissues. When RBCs are in areas of high oxygen concentration, such as the lungs, oxygen molecules bind to hemoglobin. Subsequently, when RBCs travel to areas where oxygen concentration is lower, the hemoglobin releases oxygen without the expenditure of energy. This process relies solely on the natural movement of gas from areas of higher concentration to areas of lower concentration, hence not requiring energy.

In contrast, the other processes mentioned involve mechanisms that do require energy. Cytoskeletal protein deformability is essential for RBCs to change shape as they pass through narrow capillaries, and it requires ATP for the maintenance and restructuring of the cytoskeletal framework. Preventing peroxidation of proteins and lipids involves antioxidant defenses that often depend on energy-consuming processes to regenerate antioxidants like glutathione. Lastly, maintaining cytoplasm cationic electrochemical gradients requires energy to actively transport ions across the cell membrane, which is facilitated by ATP-dependent pumps. These processes highlight the distinctions in energy utilization within RBCs, with oxygen transport being the exception that does not utilize energy directly.