Endocytosis Flashcards
What is endocytosis?
A cellular process where materials from outside the cell are taken into the cell through membrane invagination and vesicle formation.
What types of materials can be taken up through endocytosis?
Nutrients
Signals
Antibodies
Enzymes
Viruses
Bacteria
Membrane
What is phagocytosis?
The uptake of large particles such as bacteria and apoptotic cells. It involves pseudopod formation and is often facilitated by opsonization (coating of pathogens with antibodies).
What is micropinocytosis?
A type of endocytosis where cells form actin-driven ruffles that fuse to form macropinosomes. It’s mechanistically similar to phagocytosis, involves non-selective uptake of extracellular material, and is used by cancer cells to take up nutrients.
What is membrane recycling and what was the first evidence for it?
Membrane recycling is the process where internalized membrane is returned to the cell surface.
The first evidence came from studying macrophages phagocytosing latex beads: cells internalized 30% of their total surface area per hour with no change in cell size, indicating membrane must be recycled.
What is clathrin-mediated endocytosis?
A specific type of endocytosis that involves the formation of clathrin-coated pits and vesicles. It’s important for processes like LDL receptor internalization and was studied extensively by Brown and Goldstein in relation to familial hypercholesterolemia.
What is the role of dynamin in endocytosis?
Dynamin is required to pinch off clathrin-coated vesicles from the cell membrane.
This was discovered through studies of temperature-sensitive shibire mutants in Drosophila that undergo reversible paralysis.
What is the importance of pH in the endocytic pathway?
A gradient of pH is key for the function of the endocytic pathway, with different compartments maintaining different pH levels.
What are Rab proteins and their function?
Rab proteins are markers that help define different intracellular organelles along the endocytic pathway. When overexpressed (e.g., Rab5), they can affect organelle size and function.
What is a Multivesicular Body (MVB)?
A late endosome that contains intraluminal vesicles (ILVs). Cargo destined for degradation is incorporated into these ILVs.
