Secretory pathway 3 Flashcards
Is the ER or Golgi more acidic?
—Golgi
What is exocytosis?
—-movement of proteins sythesized in ER to plasma membrane or exterior of cell
Molecules released by exocytosis have at least three fates:
- They are membrane proteins and remain associated with the cell surface.
- They can become part of the extracellular matrix (e.g. collagen and glycosaminoglycans)
- They can enter extracellular fluid and signal other cells (e.g. insulin,catecholamines)
What are the 3 routes to the cell surface in exocytosis?
- Consituative secretion or direct transport
- Recycling endosomes
- Regulated secretion
What are two pathways of vesicles to the cell surface?
In polarized cells of epithelial tissue, plasma membranes are divided into apical domains and basolateral domains, each with specific proteins
What r 3 types of endocytosis?
—-phagocytosis, pinocytosis, receptor mediated endocytosis
Receptor mediated endocytosis is also called clathrin mediated endocytosis.
What form is cholestrol transported in the bloodstream as?
Cholesterol is transported through the bloodstream mostly in the form of LDL particles.
Receptor mediated endocytosis of LDL
LDL receptor - receptor mediated endocytosis
What do the internalization signals bind to?
—-adaptor proteins, which then bind to clathrin to cytoplasm
What do pits bud to form?
—-clathrin-coated vesicles
Extracellular fluids are also taken up by receptor-mediated endocytosis (fluid-phase endocytosis).
Receptor mediated endocytosis results in the internalization of an area of the cell equivalent to the entire plasma membrane every 2 hours!
What are Caveolae?
—-relatively stable, small invaginations of the plasma membrane that take up molecules
Biological roles not well understood – possibly endocytosis, cell signaling, regulation of lipid transport, protection of plasma membrane against mechanical stress
What is transcytosis?
How do early endosomes maintain an acidic pH?
—-membrane H+ pump
The early endosome acts as a sorting compartment for endocytosed materials.
Don’t forget mechanisms of vesicle trafficking - fusion of vesicles with early endosomes is mediated by Rab GTP proteins, tethering factors, and SNARE proteins.
What matures into lysosomes?
—-Late endosomes
What is the function of lysosomes?
Most lysosomal enzymes are acid hydrolases—active at pH 5 in lysosomes, but not in the cytoplasm (pH 7.2).
This prevents uncontrolled digestion of cell contents if the lysosome membrane breaks down
What are phagosomes?
What are autophagosomes?
How many degrative enzymes do lysosomes contain?
What is I-cell disease?
What is Gaucher’s disease Type I?
30 different mutation responsible for Gaucher’s disease identified - wide spectrum of clinical severity
