BIOL 2021 Chapter Notes - Chapter 13.14: Cell Membrane, Neutrophil, Phagocytosis
11 Mar 2018
School
Department
Course
Professor
Phagocytic Cells Can Ingest Large Particles
• Phagocytosis is form of endocytosis where cell uses large endocytic vesicles called phagosomes
to ingest large particles like microorganisms & dead cells
• In protozoa, phagocytosis is form of feeding: large particles taken up into phagosomes go to
lysosomes where they breakdown & used as food.
• Phagocytosis is important in animals for purposes other than nutrition
• In mammals, two important white blood cells:
o Macrophages
o Neutrophils
• Macrophage & neutrophil develop from stem cells & ingest
invading microorganisms to defend against infection
• Macrophages ingest organisms that have died by apoptosis
(red blood cells)
• Phagosomes fuse with lysosomes & injected material is
degraded.
o Ingested material remains in lysosomes forming residual
bodies that can be excreted from cells by exocytosis
o So components from phagosomes are returned to plasma
membrane via transport vesicles
• Different classes of receptors promote phagocytosis
o Component components with antibodies
o Oligosaccharides on surface of certain pathogens
o Cells that have died by apoptosis lose asymmetry in
distribution of phospholipid in plasma membrane
• Macrophages also phagocytose inanimate particles:
o Glass, latex beads & asbestos fibers
Figure 13-61 A neutrophil reshaping its
plasma membrane during phagocytosis
An electron micrograph of neutrophil
phagocytosing a bacterium, which is in
processing of dividing
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Phagocytic cells can ingest large particles: phagocytosis is form of endocytosis where cell uses large endocytic vesicles called phagosomes to ingest large particles like microorganisms & dead cells. In protozoa, phagocytosis is form of feeding: large particles taken up into phagosomes go to lysosomes where they breakdown & used as food: phagocytosis is important in animals for purposes other than nutrition. Figure 13-61 a neutrophil reshaping its plasma membrane during phagocytosis. An electron micrograph of neutrophil phagocytosing a bacterium, which is in processing of dividing. Summary: transport into cell from plasma membrane: endocytosis: cell ingest fluid, molecules & particles by endocytosis in which localized regions of plasma membrane invaginate & pinch off to from endocytic vesicles. In most cells, endocytosis internalizes large fraction of plasma membrane ever hour: cell remains same size b/c plasma membrane components (proteins & lipids) that"re endocytoses are continually returned to cell surface by exocytosis.
