Biol 4004 Exam 2 Questions

What are the two transporter proteins and what type of energy do they use?

Channel protein- passive (electrochemical gradient)

Transporter protein- passive (electrochemical gradient)

or active (ion gradient or ATP hydrolysis)

What is the role of tight junctions in the transport process (such as in the gut)

1. prevent solutes from crossing the epithelium between cells, maintain concentration gradient

2. Diffusion barrier to confine transporters to their respective membrane dominas

Describe the interactions between transmembrane proteins and the lipid bilayer

-proteins have nonpolar side chains that interact with hydrophobic region of lipid bilayer

-peptide bonds form hydrogen bonds with one another (usually maximized in alpha-helices)

-multiple strands of a protein may form rolled beta-sheets and hydrogen bond this way (forming B-barrel)

What is the most abundant lipid in the cell membrane?

Phosphotidylcholine

Where are phsophtidylethanolamine and phsophatidyleserine located within cell membranes?

inner monolayer

What is the net charge of phosphotidylserine?

Negative

Where is phoshotidylcholine located within the cell membrane?

Outer monolayer

What is a lipid raft?

Protein-protein, protein-lipid, lipid-lipid interactions localized in specialized domains

Why do cells need lipid rafts?

Normally one protein can't perform a single job but requires helpers/complexes. They form an assembly to complete tasks, and also help regulate eachother

What does phosphotidylinositol do?

Phospholipase C cleaves it to create two fragments.

1) stays there and activates protein kinase C

2) released from cytosol to activate release of Ca2+ ER

What does trypsin do?

Cleaves proteins non-specifically. It is a major protease

Why do Some β Barrels have side chains extending into lumen of the barrel?

to regulate the molecules that pass through the barrel through selective binding and size limitations

Where are oligosaccharides and disulfide bonds of glycosylated proteins found?

Noncytosolic surface (disulfide bonds don't form in cytosolic side, and these bonds are needed to help stabilized folded protein structure)

What is the main location of protein synthesis and degradation?

The cytosol

What are the 5 channels involved in neuromuscular transmission?

1. VG-Ca2+ channels on presynaptic membrane

2. Ligand-gated cation channels on postsynaptic membrane

3. VG-Na+ channels on postsynaptic membrane

4. VG-Ca2+ channels on transverse tubules of postsynaptic membrane

5. mechanically-activated Ca2+ release channels on SR

What does the ER synthesize?

Lipids and ribosomes

The ____________ is continuous with the ER membrane

outer nuclear membrane

Which organelles are topologically similar to the exterior of the cell?

ER, Golgi apparatus, lysosome, endosomes, peroxisomes

The nucleus is continuous with the ___________

cytosol

Where does gated transport occur?

through the nuclear envelope

What is required for ions to move through channels?

A concentration gradient

What maintains Na+ concentration gradient in the epithelial cells lining the gut?

Na+-K+ ATPase

What are the three forms of voltage-gated Na+ channels?

1. Active

2. Inactive

3. Closed

What is the stroma of the chloroplast identical to?

The matrix space of the mitochondria

Protein import to mitochondria, chloroplasts, nuclei, and peroxisomes is ______-translational, and import to the ER is _____-translational

post, co

What proteins do membrane-bound ribosomes synthesize?

proteins being concurrently translocated into the ER

What proteins do free ribosomes synthesize?

All other proteins encoded by nuclear geneomes

What do the inner and outer layer of vesicle coats do?

Inner selects specific membrane proteins

Outer shapes the transport vesicle

What two things do adaptor proteins bind?

clathrin triskelions and membrane-bound cargo receptors

______ ____________ __________ direct nuclear proteins to the nucleus

nuclear localization signals

What two things do nuclear import receptors bind?

1. The nuclear localization signal of the cargo/nuclear import adaptor protein

2. FG repeats in channel nucleoporins (NPC)

Where are Ran-GDP and Ran-GTP located?

GAP and GEF?

Ran-GDP and GAP: cytosol

Ran-GTP and GEF: nucleus

If a protein is targeted to the mitochondria where is it most likely synthesized?

Free ribosome

What are the differences and similarities between the endosome and lysosome?

They are both acidic.

Endosomes hold material to be degraded

Lysosome has enzymes to perform the degredation

It a protein is targeted to the nuclear membrane, where is it most likely synthesized?

Rough ER

TOM is translocator of the _____ membrane, and TIM is the translocator of the _______ membrane

outer, inner

What signal sequences are required for protein to be translocated to thylakoid space?

Chloroplast signal sequence (will be cleaved off once in stroma)

Thylakoid signal sequence

______ and _________ occurs at Rough ER, _______ occurs at Smooth ER

translation and translocation-Rough ER

vesicle budding- Smooth ER

The oligosaccharides added to the protein in the ER are subject to extesnive trimming in the Golgi appartaus. Why are the extra sugars added?

To prevent modifications/phosphorylation of mannose. (Mannose-6-phosphate acts as a signal sequence for the lysosome). the ER has many enzymes and we want to protect mannose from these enzymes and interactons

What is the purpose of trimming the oligosaccharide?

Some sugars are needed for sorting

-Mannose-6-phosphate is a signaling sugar to lysosomes and endosomes

What three things do vesicles contain?

membrane lipids

membrane proteins

soluble proteins

Proteins leave the ER in _____-coated transport vesicles

COPII

Retrieval of ER resident soluble proteins with __________-coated vesicles

COPI

Which part of the vescile should be targeted to begin uncoating?

The adaptor proteins

What are the three locations a protein could be sent to from the sorting station of the Golgi?

Endosome-> lysosome

plasma membrane

Exocytosis to outside of cell

The hydrolases of the lysosome originally come from the _______

ER

What is the purpose to coat the vesicles?

Coats aid in the formation of vesicles. SNAREs are what determine which vesicles will fuse to the membrane

__________ prevents full assembly of SNARE bundle and fusion of vesicle with plasma membrane

complexin

Roles of phosphotidylinositol

signaling

membrane pickup when forming vesicles (which portion of the membrane to use)

phagocytosis

What are the three major lipids in the membrane?

Phosphoglycerides

Sphingolipids

Sterols