Phagocytosis and Receptor Mediated Endocytosis: Lysosomes in Defense and Nutrition

Question 1

what is one of the most important functions of lysosomal enzymes?

Answer 1

the degradation of foreign material brought into the euk. cells by phagocytosis and receptor mediated endocytosis

Question 2

A–>E = steps
A. How do phagocytic vacuoles become lysosomes?
B. vesicles containing material brought into the cell by receptor mediated endocytosis also form?
C. as early endosomes fuse with vesicles from the TGN containing acid hydrolases, they mature to form…
D. Eventually, only ________________ remains in the lysosome, which becomes…
E. Some cells release their contents by…? in others?

Answer 2

A. phagocytic vacuoles become lysosomes by fusion with endosomes
B. vesicles containing material brought into the cell by receptor mediated endocytosis also form early endosomes
C. as early endosomes fuse with vesicles from the TGN containing acid hydrolases, they mature to form late endosomes and lysosomes, in which the ingested material is digested
D. eventually only ingested material remains in the lysosome, which becomes a residual body as digestion ceases
E. some cells release their contents by exocytosis; in others, accumulation of debris may contribute to cellular aging

Question 3

Autophagy- the original recycling system: what is a second important task for lysosomes?

Answer 3

the breakdown of cellular structures and components that are damaged or no longer needed

Question 4

Autophagy- the original recycling system: cellular structures that are damaged or unneeded must be broken down by autophagy (AKA…?)
What are two types of autophagy? how do they work?

Answer 4

• AKA self eating
• 2 types:
  1. Macrophagy: begins when an organelle is wrapped up in a double membrane derived from the ER, forming an autophagic vacuole (autophagosome)
  2. Microphagy: involves formation of a much smaller autophagic vacuole, surrounded by a single membrane bilayer that encloses small bits of cytoplasm rather than whole organelles

Question 5

Extracellular digestion:

• most lysosomal digestion occurs…?
• lysosomes can discharge their contents…? example?

Answer 5

• inside the cell
• outside the cell (extracellular digestion). example is fertilization of animal eggs-head of sperm releases digestive enzymes to degrade barriers protecting the egg