Chapter 8 Flashcards
What is the Endomembrane system composed of?
ER, Golgi complex, and dissolves, lysosomes, and vacuoles
What is the biosynthetic pathway?
Proteins are synthesized in the ER, modified a Golgi complex and transported to various destinations
What is the secretory pathway?
Protein synthesized in ER are discharged from cell
What is the endocytic pathway?
Materials move from outer surface of cell to compartments, endosomes and lysozymes
What are the two secretion modes?
Consecutive secretion and regulated secretion
What is consecutive secretion?
Materials transported in secretary vesicles and discharged in continual manner
What is regulated secretion?
Materials are stored in vesicles and discharged in response to stimulus
Where does regulated secretion occur?
Endocrine cell (hormones), pancreatic acinar cells (digestive enzymes), and never cells (neurotransmitters)
How can secreted materials be stored?
In large, densely packed, membrane-bound secretory granules
How are proteins, lipids, and complex polysaccharides transported through the cell?
Along the biosynthetic or secretory pathways
What is autoradiography?
Visualize biochemical processes by radioactively labelling molecules
What did autoradiography show?
Endoplasmic reticulum as site where secretory proteins synthesis occurred
What are GFPs?
Fluorescent proteins, allows microscope’s viewing of protein movement in living cells
What is the endoplasmic reticulum?
Network of membranes that penetrates much of cytoplasm and has a lumen separated from cytosol by ER membrane
What are the two compartments of the ER membrane?
The rough ER and the smooth ER
Describe the rough ER
Ribosomes bound to cytosolic surface, flattened sacs connected to neighbors, continuous with outer membrane of nuclear envelope
Describe smooth ER
Lacks ribosomes, membranes highly curved and tubular, continuous with RER
What is the SER functions?
- Steroid hormone synthesis in endocrine cells of the gonad an adrenal cortex
- Detoxification of organic compounds in liver
- Calcium ions sesquastation and regulated release
What is the starting point of biosynthetic pathways for secretory proteins?
The RER
What is co-translational translocation?
Proteins are synthesized at our ER and released into ER lumen
The ER bound ribosomes synthesize what?
Integral membrane proteins
How are integral membrane proteins synthesized?
Co translationally, and hydrophobic transmembrane segments are shunted from translocation into lipid bilayer
What are tail anchored proteins?
Lack signal sequence, are synthesized in cytoplasm, and targeted to ER through interactions with proteins in GET pathway
How do membranes arise?
From other membranes
What modifies membranes?
Enzymes
Nearly all proteins produced on RER become what?
Glycoproteins
Accumulation of miss folded proteins triggers what kind of response?
Unfolded protein response
Are misfolded proteins destroyed?
Yes
What is the first step in vesicular transport?
ER to Golgi complex
Where are transport vesicles formed?
The RER has specialized exit sites
What is the Golgi complex?
Stack of flattened cisternae
What does the cis face of the Golgi face?
The ER
Where is the trans face of the Golgi?
The opposite side of the stack
What is the cis Golgi Network?
Functions to sort proteins for the ER or next Golgi station
What is the trans Golgi network?
Functions in sorting proteins to plasma membrane or various intracellular destinations
Where does assembly of carbohydrates take place?
In the Golgi complex
Describe the vesicular transport model
Cargo shuttled from CGN to TGN in vesicles
Describe cisternal maturation model
Each cistern matures as it moves from cis to trans
How are materials carried between compartments in vesicle transport?
Using coated vesicles
What are the two functions of protein coats?
- Cause membrane to curve and form vesicle
- Select components to be carried by vesicle
What are COPII coated vesicles?
Move materials from ER forward to ER GIC intermediate compartment and Golgi complex
What are COPI coated vesicles?
Move materials from ERGIC and Golgi backward to ER or from trans Golgi to cis Golgi cisternae
What are clathrin-coated vesicles?
Move materials from TGN to endosomes, lysosomes, and plant vacuoles
What do clathrin coated vesicles contain?
An outer lattice composed of clathrin, an inner shell composed of GGA adaptor proteins, and a G protein
What are Rabs?
A family of small G proteins which cycle between an active GTP bound state and an inactive GDP bound state
What are SNAREs?
Constitute family of proteins localized to specific sub cellular compartments, integral proteins that bring vesicle and target compartment in close contact
Where are v- SNAREs found?
Transport vesicles
Where are t-SNAREs found?
Target compartments
What is exocytosis?
Discharge of a secretory vesicle or granule after fusion with plasma membrane
What is exocytosis triggered by?
Increase in calcium
What is a fusion pore?
Contacts between vesicle and plasma membranes
What are lysosomes?
Single celled organisms and phagocytic white blood cell digest ingested materials by fusing phagosomes in lysozymes
What is a phagophore?
Envelopes an organelle to produce a double membrane sequestering vesicle
What is a benefit of autophagy?
Helps protect organism from intracellular threats and may play a role in prevention of certain types of cancers
What are the two categories of endocytosis?
- Bulk phase endocytosis
- Receptor mediated endocytosis
What is bulk phase endocytosis?
Nonspecific uptake of extra cellular fluid
What is receptor mediated endocytosis?
Brings about uptake of specific extra cellular macromolecules following binding to receptors on the surface of the plasma membrane
What is dynamin?
G protein required for fission of vesicles from membrane on which it forms, self assembles into helical collar
After internalization, vesicle bound materials are transported in vesicles and tubules known as what?
Endosomes 
What are low density lipoprotein’s?
A complex of cholesterol and proteins, LDL receptors are transported to plasma membrane and bound to a coated pit
What are peroxisomes?
Small, membrane enclosed organelles that contain enzymes involved in a variety of metabolic reactions, including several aspects of energy metabolism
