Endocytosis Flashcards
What do cells take up?
- Nutrients
- Signals
- Antibodies
- Enzymes
- Viruses
- Bacteria
- Membrane
Why is a lower pH needed in the early endosome, compared to the cytoplasm, to allow entry?
As a lower pH is needed to allow for a conformational change, which allows fusion with endosomal membrane.
What are the 3 different fates for endocytosed material?
- degradation
- transcytosis
- recycling
Describe what degradation means?
Material endocytosed then transferred to lysosome for breaking down.
Describe what transcytosis means?
Movement of material across the cell (from one membrane to another)
Describe what recycling means?
Material sent back to the same membrane
What is phagocytosis (basic)?
Uptake of large particles
What is opsonization?
Pathogens are often caused by antibodies
Describe the process of phagocytosis
Pseudopods, driven by the cytoskeleton, engulf the bacteria/yeast cell, allowing the phagosome to form, and actin provides the force for the engulfing to take place.
What fate can be proven by the fact that 30% of total surface area is internalised per hour, but no change in cell size?
The membrane must be recycled
What is macropinocytosis?
Allows uptake of ECF
What is needed for macropinosomes to form?
- Cells form actin driven ruffles which sometimes fuse to form macropinosomes.
- Mechanistically similar to phagocytosis
- Non-selective uptake of extracellular material
- Used by cancer cells to take up nutrients
How selective is clathrin-mediated endocytosis?
Very selective
What is a cause of defective binding of LDL (low density lipoprotein) of defective internalisation?
Mutations in LDL receptors
What do Clathrin triskelia polymerise to form?
Lattices
