Endocytosis

Question 1

What happens to endocytosed material in a cell?

Answer 1

-some is recycled
-transcytosis - moved to other side of cell + released out of apical membrane
-degradation - taken up by lysosome + hydrolysed by enzymes

Question 2

What are the 2 types of endocytic pathways?

Answer 2

-small scale processes - forms a small vesicle
-large scale (micropinocytosis + phagocytosis) - results in more of a vacuole than a vesicle

Question 3

What is opsonisation?

Answer 3

Pathogens are often coated by antibodies

Question 4

What is phagocytosis?

Answer 4

-uptake of large particles
-bacterial antigens interact with phagocyte antibodies so can engulf the pathogen
-mobilisation of actin forms pseudopods - extend from cell + allow further engagement of antibodies with antigens

Question 5

What is frustrated phagocytosis?

Answer 5

-2 macrophages try + engulf the same bacterium
-occurs when target is too large to be completely engulfed by 1

Question 6

What is macropinocytosis?

Answer 6

-cells form actin driven ruffles which sometimes fuse to form macropinosomes
-mechanistically similar to phagocytosis
-non selective uptake of extracellular material

Question 7

What is clathrin-mediated endocytosis?

Answer 7

-low density lipoprotein (LDL) + LDL receptor enters cell by endocytosis
-enters a coated vesicle, then becomes uncoated
-vesicle fuses with endosome + becomes an early endosome
-LDL taken up by lysosome + is hydrolysed to get cholesterol
-receptor budded off of transport vesicle + returned to plasma membrane

Question 8

What is dynamin required for?

Answer 8

To pinch off clathrin coated vesicles

Question 9

What do Rab proteins define?

Answer 9

Intracellular organelles - give them identity

Question 10

What is inside a late endosome and what is it important for?

Answer 10

-has multiple vesicles inside - multivesicular body (MVB)
-the cargo in harvested for degradation
-important for switching off signals