Medical Physiology

Question 1

Very large particles enter the cell by a specialized function of the cell membrane called endocytosis. What are the 2 principle forms of endocytosis?

Answer 1

1. Pinocytosis - ingestion of minute particles

2. Phagocytosis - ingestion of large particles such as bacteria,whole cells or portions of degenerating tissue.

Question 2

Once a pinocytotic or phagocytic vesicle with a foreign substance appears inside a cell, what intracellular organelle is responsible for releasing digestive enzymes to destroy the foreign matter (i.e. bacteria)?

Answer 2

Lysosomes

• also responsible for regression of tissue (i.e.muscle after long periods of inactivity) and removal of damaged cells.
• Also contain bactericidal agents: Lysozyme (dissolves bacteria cell membrane) and Lysoferrin (binds iron to inhibit bacterial growth) and Acid (pH of 5.0 which activates hydrolases and inactivates bacterial metabolism)