Vesicular Transport, Exocytosis, Pinocytosis, Endocytosis Flashcards
What are the different types of endocytosis?
Receptor-mediated endocytosis, pinocytosis
How is iron taken up from the blood?
Transferrin binds to iron in the blood. Transferrin and iron binds to a receptor on the cell surface membrane, and is pinched off in a clathrin-coated vesicle. The clathrin coat is lost and the vesicle delivers its contents to an endosome. The low ph (4.5-5) causes a conformational change in transferrin, which releases the iron, but the transferrin remains bound to its receptor. The complex is recycled to the plasma membrane, where transferrin is released due to the neutral pH.
How is cholesterol stored in the blood?
As cholesteryl esters surrounded by free cholesterol and phospholipids surrounded by an apolipoprotein which gives the LDL structure.
How is cholesterol taken up form the blood?
The LDL binds to a receptor, which causes the pinching off of a vesicle at high concentrations to form clathrin coated vesicles. This vesicle fuses with a lysosome, hydrolysing the cholesteryl ester and releasing free cholesterol. The receptor is then recycled to the plasma membrane.
What is the difference between clathrin coated pits and calveoli?
Calveoli are shaped by calveolins which insert a small hydrophobic loop in the cytosolic monolayer, acting to curve the membrane.
Clathrin coated pits use clathrin and dynamic which recruits other proteins which help bend the membrane.
How do phagocytes digest pathogens?
The Fc receptor on the phagocyte binds to the Fc region of the antibody on the pathogen. This promotes actin nucleation around the pathogen which enables the membrane to close around it.
How do phagocytes recognise dead cells?
PS asymmetry (PS groups are negatively charged). These bind calcium ions which allow the association of annexin, which the phagocyte can recognise to digest the dying/dead cell.
What are the different types of exocytosis?
Signalled and Constitutive
What is signalled exocytosis?
Vesicles wait for a signal at the plasma membrane for fusion with their snares intwined. An example of this is in synapses, where an influx of calcium ions causes release of acetyl choline.
What is constitutive exocytosis?
Regions of the membrane with PIPs bud off continuously (e.g from the trans face of the golgi apparatus)
How does a secretory vesicle mature?
A secretory vesicle is acidified using H+ pumps which concentrates the cargo.
How do snares and Rab proteins work?
Overcome energy barrier associated with displacing the water (required to temporarily organise water molecules) by forming very tight associations with each other, allowing vesicle fusion.
What are the different types of exocytosis?
Signalled, constitutive.
