Endocytosis and Exocytosis

Endocytosis and Exocytosis
A way for molecules to enter or exit the cell without requiring them to pass through the membrane structure. Both require energetic input and utilize the cell membrane. 

A) Exocytosis
Membrane-bound intracellular vesicles merge with the cell membrane to expel its contents into the extracellular space.
  

B) Endocytosis: 
Can be thought of as the opposite of exocytosis. Membrane folds into the cell (invaginates) and pinch off to produce membrane-bound vesicles inside the cell containing extracellular components/fluids.
  
Pinocytosis: fluid endocytosis ("cell drinking")
Most cells can do this
Phagocytosis: solid endocytosis ("cell eating")
Cell engulfs bacteria, other cell debris from tissue death, etc.
Pseudopodia ("sham feet") are created to surround material
Usually specialized cells such as macrophages/other immune cells 
Receptor-mediated endocytosis: specific uptake triggered by receptor binding
Clathrin-dependent
Formation of a clathrin-coated vesicle 
Example: cholesterol binds to LDL receptor in liver and clathrin is recruited in cytoplasm and coats the vesicles from the inside
Potocytosis: clathrin-independent
Formation of tiny vesicles called caveolae that deliver their contents to cytosol 

Which of the following statement(s) are false regarding phagocytosis?

A. All cells can do phagocytosis

B. Requires the formation of pseudopodia

C. It is a type of exocytosis

D. It is when intracellular vesicles merge with the cell membrane to expel its contents extracellularly

E. Bacteria and cell debris can be "eaten" by the cell in this process

I don't know

Pinocytosis:

A. Results in the formation of a clathrin-coated vesicle 

B. Can be performed even by cells that cannot do phagocytosis

C. Is a type of receptor-mediated endocytosis

D. Vesicles are formed inside the cell and merge with the membrane

E. None are true

I don't know

Wize University Physiology Textbook > Cellular and Membrane Physiology

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