Lecture 21: Endocytosis, Autophagy, Cytoskeleton Flashcards
Clathrin is…
A coating that coats proteins and is involved in the vesicle formation and structure of the clathrin coated vesicles in the biosynthetic pathway
What is the AP complex?
Clathrin adaptor protein complex, forms the inner layer that’s sits on the inner part of the vesicle, AP complex binds the clathrin to the vesicle
How many classes of AP complexes are there?
3
What is the function of the AP complex?
Selecting cargo
Binding coat protein clathrin
What do AP/clathrin coated vesicles do?
Move material from TGN to other compartments (late endosome). They form endocytic vesicles to move material from plasma membrane/ extracellular environment into the cell.
Why do lysosomes have a low pH inside?
Proton pumps in membranes that pump protons in lysosome so that acidity increases inside. Phospholipids to FA, proteins to AA.
What happens to macromolecules once they are broken down in the lysosome?
They are pumped out of the lysosome and are released into the cytosol where they are used again
What is autophagy?
Self-eating, normal disassembly of unnecessary or dysfunctional cellular components - organelle turnover.
How does autophagy occur?
- Begins at membrane of the ER which extends (phagophore) to organelle which is to be turned over
- ER membrane (phagophore) extends around the organelle
- Phagophore forms double membrane layered vesicle - which is called an autophagosome
- Autophagosome fuses with a lysosome - forms structure called autolysosome
- Lysosomes that contain hydrolytic enzymes which degrade the organelle inside the autolysosome
- Basic compounds are released into cellular environment
Types of autophagy
- Mitophagy - degrading mitochondria
- Lipophagy - degrading lipid droplet
- Aggrephagy - degrading aggregates
- Xenophagy - degrading pathogens and viruses
Degradation of material in lysosome can be broken down into two different factors
- Recycling - endocytosis LDL
- Destroy pathogens like bacteria and viruses - only in phagocytic cells
Phagocytosis
The process in which a phagocytic cell internalizes a pathogen which is degraded by hydrolytic enzymes from lysosomes inside the phagocytic cell and are released as debris
Endocytosis vs Phagocytosis
Endocytosis - uses the broken down material and is released INSIDE the cell
Phagocytosis - does not use the degraded material broken down and is released outside the cell
Plant vacuoles are _____________ that take up ____ percent of cells volume
Fluid-filled, membrane-bound
90
The membrane that surrounds the vacuole is called the?
Tonoplast, allows ion/molecule transport in and out of vacuole
