Transport vesicle bud off from one compartment and fuse with another. As they do so, they carru material as cargo from the lumen and membrane of the donor compartment to the lumen and membrane of the target compartment.
Vesicular transport is very selective
Budding requires a membrane fusion initiated from lumen side of membrane, while vesicle fusion requires a membrane fusion event initiated from cytoplasmic side of both donor and target membranes.
The leaflets are remained impact
Vesicle transport is the formation of donor organelle (it is a membrane which contains the lipids and proteins the ones that transport of) we are going to bud to form the donor membrane and pinch off in chunk which we call a vesicle this process is called deforming and budding fission
Membrane fission is the splitting of the donor membrane vesicle
So in the end we have a transport vesicle to get protein and that vesicle is going transported of the microtubules undergoes fission, which means merging. A little vesicle containing cargo a start is taken transported to target organelle. Cell from one organelle is transported to the other organelle.
The fission is mediated by the protein called snares, snares are interact very strongly, they drive the merging of the membrane
This figure purposely labels the reflects of the bilayer into different colors: the inner luminal reflects blue, the cytosolic is in red
The order of this membrane is maintained
You don’t flip flop with composition
Topology: continuity and ability to exchange without “crossing” the membrane
The lumen of the organelles are continuous of each other and with the extracellular fluid
Cytosol is continuous with the nucleus
Functions of vesicular transport
1. Biosynthetic pathway: delivery of newly synthesized proteins and membrane from ER to most other organelles: Golgi, plasma membrane, endosomes, lysosomes (pathway involves making new things)
2. Exocytosis pathway: delivery of newly synthesized or stored proteins into the extracellular space(allows to secrete)delivering thing like: Neurotransmitters Proteolytic enzymes to kill bacteria Release of signaling peptides like growth factors and insulin
Exocytosis Vesicle contains molecules
3. Endocytosis pathway (pinching in) uptake of external and plasma membrane-bound proteins and ligands (control the cell surface) Vitamins and nutrients Cholesterol (LDL) Growth factors and receptors (control of cell growth) Changing the properties of the cell surface
They have to be balanced
In exocytosis, a transport vesicle fuses with the plasma membrane. Its content is released into the extracellular space, while the vesicle membrane (red) becomes continuous with the plasma membrane
In endocytosis, a plasma membrane patch (red) is internalized forming a transport vesicle. Its content derives from the extracellular space
Roadmap of the endocytic, biosynthetic and recycling vesicular pathways
The blue arrows denote retrieval pathway for the backflow of selection component
The red arrows are (polar transport) anterograde transport (forward transport)
--The blue arrows are refers to recycling or retrograde transport (reverse step)
-- Green is the endocytic trafficking, molecules are ingested in vesicle derived from plasma membrane and derived to early endosomes and then to lysosome
--When the mechanisms go wrong you can get diseases
-- In the biosynthetic secretory pathway (red arrows) protein molecules are transported from the ER to the plasma membrane or to lysosome.
FACT 1: There are at least 10 distinct compartments in the biosynthetic-secretory and endocytic pathways
Question 1: How is membrane trafficking managed between all these organelles?
FACT 2: There is constant and rapid membrane flow between organelles, i.e., organelles are effectively continuous
Question 2: How come all these organelles…