Endomembrane System

Question 1

O-linked Glycosylation

Answer 1

binding of sugars to -OH of serine, threonine and in collagen to hydroxylysine

Question 2

What signal directs proteins into lysosomes?

Answer 2

Mannose-6-phosphate

Question 3

Pinocytosis

Answer 3

the ingestion of liquid into a cell by the budding of small vesicles from the cell membrane

Question 4

Caveolae

Answer 4

a special type of lipid raft, are small (50–100 nanometer) invaginations of the plasma membrane in many vertebrate cell types, especially in endothelial cells and adipocytes

Question 5

Transcytosis

Answer 5

transcellular transport in which various macromolecules are transported across the interior of a cell. Macromolecules are captured in vesicles on one side of the cell, drawn across the cell, and ejected on the other side

Question 6

What are the functions of the Endoplasmic Reticulum?

Answer 6

transmembrane protein and lipid synthesis, lysosomal protein synthesis, lipid synthesis for organelle synthesis

Question 7

What is the purpose of the Smooth ER?

Answer 7

lipid synthesis, detoxify lipid soluble drugs, sequester calcium, and repair proteins

Question 8

How are ribosomal complexes directed to the ER?

Answer 8

N-terminal signal peptides

Question 9

What is a SRP?

Answer 9

Signal Recognition Particle that binds to the signal sequence of polypeptide and then binds to its receptor in the rough ER

Question 10

Translocon

Answer 10

a complex of proteins associated with the translocation of polypeptides across membranes.

Question 11

Which sub-unit of the Ribosome binds to the protein translocator in the ER membrane?

Answer 11

Large Ribosomal subunit

Question 12

How is the Nascent peptide inserted into the translocon?

Answer 12

GTP binding and hydrolysis

Question 13

What are the steps leading to insertion of protein into translocon?

Answer 13

GDP-SRP binds to signal sequence of polypeptide ribosome complex, GDP exchanged for GTP, complex binds to SRP receptor on the membrane of ER, hydrolysis of GTP results in release of the SRP-receptor and insertion of the nascent peptide into the translocon and release of the SRP

Question 14

Sector 61 complex

Answer 14

an endoplasmic reticulum (ER) membrane protein translocator

Question 15

Post-translational Translocation

Answer 15

Translocation happens after the polypeptide has been translated

Question 16

Co-Translational Translocation

Answer 16

Translocation happens while the polypeptide is being translated

Question 17

What do Stop transfer signal do?

Answer 17

Anchor the protein in the membrane

Question 18

What are the steps to the anchoring of protein in the membrane?

Answer 18

Start signal on the protein binds the translocon. The peptide moves through the translocon until it reaches the stop transfer signal which binds to the translocon. These 2 hydrophobic regions are moved from the translocon to the membrane and stay anchored

Question 19

N-linked Glycosylation

Answer 19

most common form of glycosylation where sugars are attached to sparagine residues

Question 20

How do complex sugars end up in the ER?

Answer 20

Sugars are added to dolichol phosphate (which is in the ER membrane) in the cytosol using oligosaccharyl transferase. the sugars are then flipped across the membrane into the ER lumen

Question 21

What happens in the Gogli?

Answer 21

the modified glycosylated proteins are trim and added with additional sugar

Question 22

How are misfolded proteins destroyed in the cytosol?

Answer 22

they are tag with ubiquitin and chopped up in the proteasome

Question 23

GPI

Answer 23

glycoslyphosphatidyl inositol used as a lipid anchor to attach proteins to the membrane

Question 24

Where are most membrane lipids synthesized?

Answer 24

ER

Question 25

How are lipids moved within the cell?

Answer 25

phospholipid exchange protein