Final answer:
Inhibition in protein-mediated transport can be caused by the saturation of carrier proteins, inhibitors affecting protein synthesis or functionality, and genetic conditions leading to defective receptor-mediated endocytosis.
Step-by-step explanation:
Various factors can cause inhibition in protein-mediated transport across cellular membranes. One key factor is the saturation of carrier proteins, as there is a finite number of these proteins available in any given membrane. When they are all bound with their respective ligands, the rate of transport reaches its maximum and cannot be increased even if the concentration gradient is increased.
Another cause of inhibition includes the presence of inhibitors that impact protein synthesis or the protein’s functionality directly. Certain drugs and antibiotics are known to inhibit protein synthesis by targeting the protein production mechanisms in cells. Additionally, some proteins act as regulators, such as IK-B which, upon binding to NF-kB, prevents it from entering the nucleus and initiating transcription, thus controlling the transport process.
Lastly, some diseases, like familial hypercholesterolemia, result in an inhibition of transport due to defective receptor-mediated endocytosis, where substances fail to be removed from blood or tissue fluids, leading to the accumulation of harmful substances like LDL cholesterol.