Biology, Eighth Edition (Raven)

Chapter 51: The Immune System

Phagocytosis

Phagocytosis is a specialized example of what widespread cellular process? Phagocytes are specialized cells that ingest and break down foreign material, including bacteria and viruses. Although they are components of the body rather than independent units, phagocytes are similar to single celled organisms such as amoebas. Amoebas move through a liquid environment and engulf organic material both unloving and living. The material is broken down inside the cell and used as a source of energy and nutrients. Excess molecules are removed from the cell. The process of bringing material into the amoeba’s cell is called endocytosis and the process of removing material from the cell is called exocyotsis. Phagocytosis is a specialized form of endocytosis and exocytosis.

View the animation below, then complete the quiz to test your knowledge of the concept.


1.	Phagocytes are attracted by all of the following except

		A)	phospholipids released by injured cells
		B)	components of the complement system
		C)	chemical products of microorganisms
		D)	lysosomes

2.	In phagocytosis the digested contents are eliminated by

		A)	endocytosis
		B)	exocytosis
		C)	opsonization
		D)	C3b

3.	A lysosome

		A)	is found only inside the bacterium being ingested
		B)	is an organelle that makes a bacterium motile
		C)	contains lysozyme and proteases which digest bacteria
		D)	contains enzymes specific to the receptors on the bacterium being eliminated

4.	Complement factor C3b coats a bacterium and binds to C3b receptors on phagocytes, making the bacterium more susceptible to being phagocytized.

		A)	True
		B)	False

5.	A phagosome containing the engulfed bacteria combines with a lysosome containing enzymes to produce a phagolysosome.

		A)	True
		B)	False