12 Questions
What is the primary function of carrier and channel proteins in the cell membrane?
To transport small molecules through the phospholipid bilayer
What is the term for the process by which cells take up macromolecules and particles from the surrounding medium?
Endocytosis
What is the characteristic feature of phagocytosis?
Intake of molecules larger than 0.1 microns into the cell with cell membrane extensions
Which type of endocytosis is involved in the uptake of specific macromolecules?
Receptor-mediated endocytosis
What is the ultimate fate of the ingested material during endocytosis?
It undergoes a chemical change and is digested in the vesicle
Who is credited with the discovery of endocytosis?
De Duve
What is the primary function of phagocytosis in mammals?
To provide a defense against invading microorganisms
What is the structure formed when a phagocytic cell engulfs a particle?
Phagosome
Which type of white blood cell is responsible for phagocytosis in mammals?
Neutrophils and Macrophages
What is the purpose of pseudopodia in phagocytosis?
To extend the cell surface to surround a particle
What is the size range of particles that can be engulfed by phagocytosis?
1-2 micrometers
What is the final step of phagocytosis?
Digestion of the particle
Study Notes
Endocytosis
- Eukaryotic cells can take up macromolecules and particles from the surrounding medium through a process called endocytosis
- During endocytosis, the material is surrounded by plasma membrane, which then buds to form a small vesicle containing the ingested material
- The substance undergoes a chemical change in the vesicle, is digested, and passes into the cytosol
Types of Endocytosis
- There are three major types of endocytosis:
- Phagocytosis (cell eating): ingestion of large particles
- Pinocytosis (cell drinking): uptake of fluids
- Receptor-mediated endocytosis: selective uptake of specific macromolecules
Phagocytosis
- Phagocytosis is the intake of molecules larger than 0.1 microns into the cell with cell membrane extensions
- Cells engulf large particles (1-2 micrometers) such as bacteria, fungi, apoptotic cells, damaged or aged cells, dead cells, and cell debris
- In mammals, phagocytosis is the function of two types of specialized white blood cells: professional phagocytes (macrophages and neutrophil granulocytes)
Steps of Phagocytosis
- Binding of particle to the receptors on the surface of the phagocytic cell (attachment)
- Extension of pseudopodia (an actin-based movement of the cell surface)
- Pseudopodia surround the particle, membranes fuse to form a large vesicle phagosome (>0.25 μm) (engulfment)
- Phagosomes fuse with lysosomes
- Digestion of the particle
Importance of Phagocytosis
- Provides a defense against invading microorganisms
- Eliminates aged or damaged cells
Learn about receptor mediated endocytosis, a process by which eukaryotic cells take up macromolecules and particles from the surrounding medium. This quiz covers the basics of endocytosis and its role in cellular biology.
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