Lecture 8

Question 1

what defines the endomembrane system (5)

Answer 1

collection of membrane enclosed organelles

endoplasmic reticulum
Golgi apparatus
endoscomes
lysosomes
peroxisomes

Question 2

what are the general functions of the endomembrane system (2)

Answer 2

regulate protein trafficking
metabolism

Question 3

where does the synthesis of lipids/proteins/plasma membrane occur

Answer 3

ER

Question 4

where does intracellular degradation occur

Answer 4

lysosomes

Question 5

where does oxidative breakdown of toxic molecules occur

Answer 5

peroxisomes

Question 6

what organelle takes up 22% of the cell

Answer 6

mitochondria

Question 7

why is endomembrane system only within eukaryotic cells

Answer 7

because prokaryotic cells dont have membrane bound organelles

Question 8

what does the endomembrane system do

Answer 8

allows cells to shuttle different substances or molecules to different regions of the cell

Question 9

what is budding

Answer 9

bud from donor membrane compartment

Question 10

how do vesicles move in the endomembrane system

Answer 10

via motor proteins that form tracks

Question 11

what are the tracks for vesicle transport made of

Answer 11

microtubules and microfilaments of the cytoskeleton

Question 12

what is fusion

Answer 12

fusion with membrane of acceptor compartment

Question 13

what is the biosynthetic pathway also known as

Answer 13

secretory

Question 14

what are the steps to the transportation of protein

Answer 14

proteins synthesized in the ER
modified at Golgi complex
transported to various destinations

Question 15

what is the endocytic pathway ? what are examples of organelles invloved

Answer 15

material moving from outer surface of cell to compartments inside (recycling)

ie endoscopes and lysosomes

Question 16

what are the two modes of secretion for the secretory pathway

Answer 16

constitutive
regulated

Question 17

what is the constitutive secretory pathway? does it need a trigger?

Answer 17

materials transported in secretory vesicles

and discharged CONTINUOUSLY

does not need a trigger

Question 18

what is the regulated pathway in secretary pathway? does it require triggers?

Answer 18

selectively releasing secretary granules

triggers are hormones and epinephrine

Question 19

what kind of things are delivered in constitutive secretionn

Answer 19

lipids/proteins

Question 20

what kind of things are released in the regulated secretory pathway

Answer 20

hormones/neurotransmitters/enzymes

Question 21

which type of the secretory pathway requires a signal transduction

Answer 21

regulated

Question 22

what do acinar cells do

Answer 22

they are involved in producing and secreting digestive enzymes

Question 23

how do we connect ER sheets

Answer 23

helicoidal ramps

Question 24

whats the structural difference between smooth and rough ER

Answer 24

smooth is more tubule like
rough is flattened and has ribosomes

Question 25

does the ER contain cisternae

Answer 25

yes

Question 26

which part of the ER is continuous with the nuclear envelope

Answer 26

the rough ER

Question 26

where does steroid hormone synthesis in endocrine cells occur

Answer 26

the smooth er

Question 27

what sequesters calcium in muscle cells

Answer 27

sarcoplasmic reticulum

Question 28

what are the 3 functions listed of the smooth ER

Answer 28

lipid and steroid synthesis Detoxification of Drugs and Toxins Calcium Storage and Release

Question 29

what are polyribosomes

Answer 29

group of ribosomes attached to the same mRNA

Question 30

what is cytoskeleton protein made by

Answer 30

free ribosomes in the cytosol

Question 31

what is everything secreted by the cells from

Answer 31

the ER

Question 32

what is co translational translocation

Answer 32

proteins being synthesized in ribosomes and being transported into the ER at the same time

Question 33

how do ribosomes in the cytosol becomes associated with the ER membrane?

Answer 33

nascent polypeptide that contains a signal sequence

Question 34

what determines the synthesis site of proteins

Answer 34

the sequence of amino acids in N-terminal portion of polypeptide determines synthesis site

Question 35

what is a signal hypothesis

Answer 35

proteins built in "address codes" of where they belong

Question 36

what recognizes signal sequences on ribosomes and helps it to the ER membrane

Answer 36

signal recognition particle (SRP)

Question 37

what does a signal recognition particle stop

Answer 37

proteins synthesis until it leaves

Question 38

what does an SRP do

Answer 38

recognizes signal sequence on ribosomes attaches and interacts with an SRP receptor on the ER membrane once attached, it attaches the ribosomes signal sequence to a translocon and leaves co transitional translocation occurs and protein continues to be synthsized into the ER signal sequence is removed and recycled

Question 39

what is a translocon

Answer 39

channel protein in the ER membrane

Question 40

what kind of proteins are SRP + SRP receptor

Answer 40

G proteins (require GTP)

Question 41

what triggers release of SRP

Answer 41

GTP hydrolysis

Question 42

what removes the signal sequence from the ribosome

Answer 42

signal peptidase

Question 43

what stops the synthesis of integral membrane proteins

Answer 43

the hydrophobic transmembrane sequence (stop transfer sequence)

Question 44

do single spanning membrane proteins change their orientation

Answer 44

no always remains the same

Question 45

how do multi spanning protein differ in synthesis compared to the single spanning ones

Answer 45

they have a start and stop hydrophobic region to have 2 domains within membrane

Question 46

what do most RER synthesized proteins become

Answer 46

glycoproteins to form a glycocalyx

Question 47

what does a glycosyltransferase do

Answer 47

add sugars to oligosaccharides

Question 48

what molecules will sugars be added 1 by 1 to in the ER membrane? what enzyme does that?

Answer 48

dolichol phosphate glycosyltransferase

Question 49

what enzyme transfers the whole group of sugars to _____________

Answer 49

oligosaccharyl transfers all of it to asparagine

Question 50

whats the huge 14 unit sugar arrangement

Answer 50

2 N-acetylglucosamines 9 Mannose 3 glucose

Question 51

what is N glycosylation

Answer 51

the process of transferring the 14 unit sugar to asparagine in the ER lumen

Question 52

many proteins are glycosylated on ______ residues in the ER

Answer 52

asparagine

Question 53

what is glycoprotein folding assessed by

Answer 53

conformation sensing enzyme UGGT protein

Question 54

what does UGGT look for to identify misfolded proteins? what do they do to them?

Answer 54

exposed hydrophobic amino acid residues on the outside that we'd expect inside they tag them with glucose and send them back to calnexin

Question 55

if multiple attempts of fixing protein misfiling doesn't work, then what happens?

Answer 55

a mannose is removed from it and it is sent to cytosol and is destroyed by proteosomes

Question 56

what does calnexin do

Answer 56

folds proteins as a molecular chaperone

Question 57

where is calnexin found

Answer 57

ER

Question 58

what does an accumulation of misfiled proteins trigger

Answer 58

unfolded protein response

Question 59

what is the protein sensor that monitors amount of misfolded proteins inactivated by

Answer 59

BiP

Question 60

what does the accumulation of protein do to BiP

Answer 60

makes BiP incapable of inhibiting the sensors which makes the sensors initiate a trigger response

Question 61

whats the trigger response that is initiated by BiP leaving the sensors

Answer 61

the sensors trigger proteins involved in destruction of misfolded proteins

Question 62

do membranes arise from pre existing membranes

Answer 62

yess

Question 63

where is ER asymmetry established

Answer 63

ER

Question 64

how does a membrane change lipid composition

Answer 64

enzymatic modification of lipid head group including or excluding different phospholipids lipid transfer proteins