Intracellular compartments: lecture

Question 1

Where’s the ER in relation to the nuclear membrane?

Answer 1

They’re attached

Question 2

Where are membrane-bound polyribosomes?

Answer 2

Some in the ER

Question 3

Is most membrane on the outside or inside of cell?

Answer 3

inside

Question 4

What cellular component makes up most cell volume in the table?

Answer 4

Mitochondria

Question 5

Do all cells have the same amount of organelles?

Answer 5

No, changes based on cell type

Question 6

What organelle changes most in abundance between liver / pancreatic cells?

Answer 6

rough/smooth ER

Question 7

First eukaryotic cell - what happened to cell wall?

Answer 7

Dissolved, and so other genes came in

Question 8

First eukaryotic cell - how did DNA get trapped?

Answer 8

Membrane folded in to anaerobic bacteria over time - protect it

Question 9

When were the first eukaryotic cells aerobic?

Answer 9

When they engulfed mitochondria

Question 10

What do vesicles need to move from one compartment to the next?

Answer 10

membranes with similar compositions

Question 11

Can all membranes move things to all other membranes?

Answer 11

No, only similarly-composed membranes

Question 12

Can all membranes move things to all other membranes?

Answer 12

No, only similarly-composed membranes

Question 13

What does the smooth ER do?

Answer 13

Makes membranes for other organelles

Question 14

How do membranes get moved to other compartments?

Answer 14

Vesicles

Question 15

Transport: What is the only organelle with gated transport?

Answer 15

Nucleus/cytosol

Question 16

What is transmembrane transport? How many organelles do it?

Answer 16

4 organelles

Question 17

What’s it called when a vesicle is just leaving?

Answer 17

budding

Question 18

What’s it called when a vesicle gets to target compartment?

Answer 18

Fusion

Question 19

How to proteins know which destination to go to?

Answer 19

Amino acid sequences specify destination (signal sequence)

Question 20

Where are destination-specifying sequence signals normally on the protein?

Answer 20

N-terminus

Question 21

Which mRNA end does n-terminus correspond to?

Answer 21

5’

Question 22

What is ‘cannonical’ ER mean?

Answer 22

well-conserved

Question 23

What kind of transport is nucleus/cytosol?

Answer 23

Gated

Question 24

What shape are nuclear pores?

Answer 24

Kinda like a basket

Question 25

What are nuclear porins?

Answer 25

They make up nuclear pore complexes

Question 26

What do nuclear pore complexes do?

Answer 26

Transport macromolecules

Question 27

What does the ER do?

Answer 27

Fold proteins, transport proteins

Question 28

What are the role of peroxisomes?

Answer 28

Destroy fatty acids / alcohol, make toxic byproducts

Question 29

What reactions do peroxisomes do?

Answer 29

Oxidation reactions. Generral reaction: H2O2 > 2H2O + O2

Question 30

What are peroxins?

Answer 30

Proteins which participate in import process for peroxisomes

Question 31

What happens between ER and peroxisome?

Answer 31

Budding vesicle > proteins attach that catalyze import > fusion Breaks up into two daughter peroxisomes

Question 32

What happens between ER and peroxisome?

Answer 32

Peroxisomal precursor leaves ER > attaches to proteins (peroxins??) > turns into peroxisome. Peroxisome grows from new input and eventually can divide

Question 33

How does ER transport to cytosol?

Answer 33

Transmembrane transport

Question 34

What is co-translational translocation?

Answer 34

Ribosome binds to ER as polypeptide is getting made

Question 35

What is the signal hypothesis?

Answer 35

Signal to go to ER is in the N-terminus of growing amino acid

Question 36

What is a protein translocator?

Answer 36

Lets protein into ER. Protein goes through it

Question 37

What do signal peptidases do?

Answer 37

Clip off signal sequence in translation

Question 38

What's a signal sequence, where is it, and what happens to it?

Answer 38

Sequence on N-terminus of growing polypeptide that signals to go to ER. Gets clipped off by signal peptidase during polypeptide growth

Question 39

What's a signal sequence, where is it, and what happens to it?

Answer 39

Sequence on N-terminus of growing polypeptide that signals to go to ER. Gets clipped off by signal peptidase during polypeptide growth

Question 40

What does an SRP do?

Answer 40

SRP (signal recognition particle) recruits cytosolic ribosomes

Question 41

What is an SRP made off?

Answer 41

single RNA, 6 protein subunits

Question 42

What does an SRP do?

Answer 42

SRP (signal recognition particle) recruits cytosolic ribosomes shuttles ribosomes to ER

Question 43

What is an SRP made off?

Answer 43

single RNA, 6 protein subunits

Question 44

How does an SRP work?

Answer 44

Moves between ER and cytosol, binds to receptor on ER

Question 45

When SRP binds, what happens with translation?

Answer 45

Pauses

Question 46

When SRP with ribosome gets to ER, what happens?

Answer 46

SRP is released/recycled, protein gets translated into ER through protein translocator

Question 47

What's the difference between free ribosome cycle and membrane-bound ribosome cycle?

Answer 47

Free = polyribosomes in cytosol Membrane-bound = polyribosome bound to ER

Question 48

How might mRNA get near an ER?

Answer 48

Polyribosomes are moved to ER with SRP; mRNA comes along for the ride

Question 49

What is the sec61 complex also called?

Answer 49

protein translocator

Question 50

How does translocator protein work molecularly?

Answer 50

There's a plug in it normally ER binding displaces the plug Polypeptide fills space of plug, threads through into ER

Question 51

Where on ribosome does the protein translocator/sec61 complex bind?

Answer 51

Large subunit

Question 52

How much energy is required for translocation to ER?

Answer 52

None!

Question 53

What did we learn about in regards to pre-translational translocation?

Answer 53

SRP, translocator, etc

Question 54

What does BiP stand for?

Answer 54

'binding protein'...

Question 55

What is BiP? What does it do?

Answer 55

Feed protein w/ ATP into ER pore and into lumen Helps fold (helps function as euk molec chaperone)

Question 56

What is 'topological equivalence'?

Answer 56

Protein can get from one place to another without going through a membrane

Question 57

What's in the nuclear lamina?

Answer 57

A shitload of proteins, it's a fibrous network

Question 58

What are NPC's made up of?

Answer 58

Nucleoporins

Question 59

How are new peroxisomes formed?

Answer 59

They're grown. First a lipid precursor grows from the rough ER and goes into cytosol Then it merges with some proteins in the cytosol (peroxisomal precursor proteins) and lipids from the smooth ER. They know to go to peroxisome from short signal sequence then it starts nomming on chemicals and releasing H2O2

Question 60

What is the ER lumen?

Answer 60

Space in between ER and nucleus, continuous with both

Question 61

When might SRPs experience a conformational change?

Answer 61

When they bind to a signal sequence, opens an area for them to bind to receptor on ER