Module 2: Lesson 3 Flashcards
What is the function of the ER in respect to proteins?
The making, modeling, and quality control of proteins.
Most proteins are modified in what way in the ER?
Covalently modified
What stabilizes a favored protein conformation?
Disulfide bonds
What is N-linked glycosylation and why is it beneficial?
ER resident enzymes transfer an oligosaccharide to N amino acids. The oligosaccharide helps proteins fold, thus controlling the quality of proteins.
What are the purposes of polysaccharides on proteins and lipids?
To prevent protein degradation; proper protein folding; some sugars serve as charged binding sites for other proteins; signal for sorting; and most proteins secreted outside the cell or membrane proteins on the cell surface of glycosylated.
What is unfolded protein response (UPR)?
Upon the accumulation of unfolded/misfolded proteins, UPR triggers an increase of chaperone genes and remodeling to increase the size of the ER.
What are the steps of UPR?
Increase the capacity of ER to fold proteins, stop new protein being made, destroy unfolded proteins, reduce the flow of proteins from ER, and activate cell death pathways.
What is the role of the proteasome in UPR?
The proteasome acts of proteins marked for cell death by covalently binding to ubiquitin.
What makes the signal for cargo receptor proteins to package cargo proteins into a vesicle?
Properly folded, glycosylated proteins are trimmed of three molecules of glucose.
What types of cisternae make up the Golgi apparatus?
cis, medial, and trans cisternae
What is formed when vesicles from the ER shed their COPII coats?
The ER and Golgi begin to fuse together, forming the ER-Golgi Intermediate Compartment (ERGIC).
What is the function of the Golgi with respect to proteins?
The glycosylation of proteins is modified, and other post-translational modifications are made by Golgi-resident enzymes. Some modifications occur in an orderly step-wise manner, hence the cisternae compartmentalization.
What is constitutive exocytosis?
Secretory vesicles take cargo from the Golgi to the plasma membrane continuously.
What is regulated exocytosis?
Secretory vesicles accumulate near the plasma membrane and then fuse only in response to specific cell signaling.
What is pinocytosis?
A type of endocytosis involving “cellular drinking”, the take up of fluids and molecules.
How does the main sorting station of the endocytic pathway function?
Early endosomes are just beneath the surface of the plasma membrane. The acidic environment of the endosomal lumen causes many receptors to release their cargo.
What are late endosomes sometimes called?
Multivesicular bodies, as sometimes there are small vesicles within the lumen of the late vesicle.
What are the three pathways from the endosomal compartment?
Recycling, degradation, and transcytosis.
What is the function of the lysosome?
Lysosomes carry out intracellular digestion of macromolecules. They contain about 40 types of hydrolytic enzymes, including proteases, nucleases, glycosidases, and phospholipases.
