Answer
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A red blood cell plasma membrane needs transmembrane proteins because the lipid bilayer alone cannot carry out essential functions. These proteins allow selective transport of ions, nutrients, and waste products that cannot cross the hydrophobic lipid core, helping the cell maintain its internal environment. They also connect the membrane to the underlying cytoskeleton, providing mechanical stability and flexibility that enable the biconcave shape of the cell and allow it to deform as it passes through narrow capillaries.
Additionally, many transmembrane proteins carry carbohydrate groups that serve as blood group antigens and facilitate cell recognition and signaling. Without these proteins, the red blood cell would be unable to control its internal composition, maintain its shape, or communicate with other cells, making transmembrane proteins essential for its survival and proper function.
