Question

Receptor-mediated endocytosis could involve of the processes described below EXCEPT......

A. hormones being secreted outside the cell.

B. the uptake of excess cholesterol by cells in blood tissue.

C, receptor proteins to bind to specific molecules.

D. a coated vesicle pit forms which then eventually becomes a coated vesicle inside the the cell.

E. a type of bulk transport.

Answer 1

Answer- A. Hormones being secreted outside the cell

Explanation- Hormones are secreted outside cell by exocytosis process. Hormones are stored in secretory vesicles and upon stimulus these vesicles fuses with cell membrane and exocytose the contents that is hormone outside cell and this process is called as exocytosis and it is not receptor mediated endocytosis which is opposite process in which substances are taken inside cell from outisde.

The process that involves receptor mediated endocytosis are -

B. Uptake of excess cholesterol by cells in blood tissue- the LDL contains large amounts of cholesterol as compared to other lipoproteins, so that when cholesterol is required by the cell, LDL is internalized by binding LDL with LDL receptor and then by receptor mediated endocytosis LDL is take up by cell, then vesicle fuses with lysosome where it degrades LDL and cholesterol is released into cell.

C. Receptor proteins to bind to specific receptors - in some cases of receptor mediated endocytosis, ligand like protein binds to specific receptor found on cell membrane and protein-receptor complex is internalized.

D. a coated vesicle pit forms which then eventually becomes a coated vesicle inside the cell- clathrin coated pits are present in cell membrane and are used for receptor mediated endocytosis. During endocytosis, clathrin coated pits are internalized and then it becomes clathrin coated vesicles and carry substance from outside to inside cell.

E. a type of bulk transport- bulk transport includes transport of substances inside or outside cell via vesicles that include exocytosis, pinocytosis, phagocytosis and receptor mediated endocytosis.