Which of the following processes allows cells to concentrate material that is present only in very small amounts in the extracellular fluid? a) phagocytosis b) pinocytosis c) receptor-mediated endocytosis d) transcytosis

C

Explanation:

The receptor-mediated endocytosis is a highly controlled process that allows cells to internalize molecules that are not very abundant in the extracellular fluid. In this type of endocytosis, the process is not mediated by a concentration gradient, in contrast it’s mediated by receptors (proteins found in the cellular membrane that are specific for the endocytosed molecules). By generating a very specific bind between the molecules within the extracellular fluid and the receptors, this process is efficient and selective even when the concentration of these molecules is low.  

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