Exocytosis and Endocytosis

Question 1

Two main types of endocytosis

differ according to the size of the endocytic vesicles formed. They are:

Answer 1

Phagocytosis and pinocytosis.

Question 2

In phagocytosis

(“cell eating”), large particles are ingested via large vesicles called

Answer 2

phagosomes

Question 3

In pinocytosis (“cell drinking”), fluid and
solutes are ingested via small

Answer 3

pinocytic vesicles

Question 4

Macrophages scavenge

Answer 4

senescent cells

Question 5

Professional phagocytes in mammals are two classes of white blood cells:

Answer 5

macrophages and neutrophils

Question 6

Phagocytosis is a _______ process.

Answer 6

triggered; requires activation of receptors that transmit signals to the cell interior and initiate the response

Question 7

Pinocytosis is a _______ process.

Answer 7

constitutive; occurs continuously

Question 8

Endocytotic pathway?

endocytosed vesicle ->

Answer 8

early endosome (low pH, dissociation of substrate from receptor) -> back to membrane or late endosome -> lysosome

Question 9

What does clathrin do?

Answer 9

It is a large protein that assists in the formation of a coated pit on the inner surface of the plasma membrane of the cell.. This pit then buds into the cell to form a coated vesicle in the cytoplasm of the cell.

Question 10

Exocytosis is the

Answer 10

fusion of the vesicles with the plasma membrane (which is made of phospholipid bilayer)

Question 11

Two secretory pathways:

Answer 11

constitutive and regulated

Question 12

Three pathways of protein sorting in the trans Golgi network:

Answer 12

1. Signal-mediated diversion to lysosomes
2. Signal-mediated diversion to secretory vesicles (for regulated secretion)
3. Constitutive secretory pathway

Question 13

Transcytosis in the indirect plasma membrane protein sorting pathway?

Answer 13

A protein is retrieved from the inappropriate plasma membrane domain (apical/basolateral) by endocytosis and then transported to the correct domain via EARLY ENDOSOMES.