Membrane transport: Secondary Active transport Flashcards
Define Endocytosis
Taking in of molecules or particles by invagination of cell membrane forming a vesicle, while the integrity of the plasma membrane is maintained
Requires energy
Followed by exocytosis on the other side- transcytosis, vesicle trafficking, or cytopempsis
Define Pinocytosis
Pino indicates small molecules ingested, forming a vesicle immediately. Seen in the small intestine cells (villi).
The plasma membrane is penetrated by the molecules and carried by a vesicle
Define Phagocytosis
Phago indicating large particles which are visible with a light microscope are invaginated into the cell.
An example is white blood cells eat bacteria.
Pseudopodium opens up and pulls in the particle, the particle is carried by a food vacuole.
Explain Receptor-mediated Endocytosis
Integral proteins have receptors on their surface to recognize and take in hormones, cholesterol etc.
Receptors bind to the molecules and capture them, move into a coated pit and develop a vesicle
Leads to fusion with endosome which is converted into a lysosome
During this, the endosome is recycled through budding of transport vesicles
Followed by the return of LDL receptors to plasma membrane
Explain Clatherin-dependent endocytosis
Receptor binds to molecule which is attached to AP-2 complex
Clathrin binds to the AP-2 complex leading to the formation of clathrin-coated vesicles
After is uncoated and AP-2 and clathrin is recycled through uncoating
Fusion leads to early endosomes leading to multivesicular bodies (MVB)
Endosomes are recycled
Lysosomes are released
Define Exocytosis
Reverse of endocytosis
Cell releases the contents of a vesicle outside of the cell
Contents maybe wastes, proteins, hormones or products from secretion
Requires energy
Give an example of Exocytosis
Vesicles from golgi fuse with plasma membrane, proteins released outside of the cell.
What is the role of the Secretory vesicles?
Carries the molecules to be secreted out of the cytoplasm into the extracellular fluid
What mediates the fusion of vesicle with plasma membrane?
Mediated by number of accessory proteins such as snare protein
Requires: Stimulus and Ca
What is an exception of a exocytosis reaction that doesn’t require stimulus?
Renin from JG cell and PTH from parathyroid glad by a decrease in intracellular Ca
Explain constitutive secretion
Immunoglobulin from plasma cell and collagen from fibroblast
What regulates exocytosis?
Endocrine gland, pancreatic acinar cells
What does the specific protein on synaptic vesicles do?
Directs them to receptor on plasma membrane, helped by other proteins such as SNAP’s
Target sites such as the plasma membrane would have corresponding?
t-SNARE (syntaxin and SNAP-25)
At sites other than the nerve terminal specific vesicle and target SNAREs would function to?
to target vesicles to specific compartments
