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BCMB2002 > Week 7 > Flashcards

Week 7 Flashcards

1
Q

LDL particle binds to _____

A

ApoB protein

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2
Q

When the LDL particle binds to the LDL receptor, what does this cause?

A

Conformation change and then clathrin and AP2 complex can come and coat it

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3
Q

When the vesicle uncoats, it is a _____ endosome

A

an early endosome

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4
Q

How is the LDL particle released?

A

Early endosome fuses with late endosome which has a low pH and the LDL particle is released

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5
Q

The late endosome fuses with the ____

A

lysosome

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6
Q

T/F:

Endocytosis is a fast process

A

False

Slow

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7
Q

T/F:

Clathrin mediates transport from the golgi to the membrane and anything in between

A

True

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8
Q

T/F:

COPI mediates transport from the ER to the golgi

A

False

It mediates transport from the golgi to the ER and to move around the golgi

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9
Q

T/F:

COPII mediates anterograde transport

A

True
transport from the ER to the golgi
Forwards

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10
Q

T/F:

COPI mediates retrograde transport

A

True
Moving from the golgi to the ER
Backwards

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11
Q

Coated vesicle assembly is initiated by recruitment of a small ______

A

GTP binding protein

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12
Q

T/F:

Early stages of the secretory pathway is vesicle mediated trafficking between the ER and trans-golgi

A

False

between the ER and cis-golgi

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13
Q

COPII is a complex of __ proteins.

A

3 proteins

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14
Q

What binds to the Sec24 component of COPII?

A

A tripeptide (acidic) signal peptide

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15
Q

What is Sar1 and what does it bind to?

A

GTP binding protein

Binds to Sec12 and causes hydrolysis to form a GTP with its hydrophobic N terminus embedded in the membrane

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16
Q

What happens when the last sec23/24 of COPII binds to the vesicle?

A

Causes a conformational change in Sar1 which causes hydrolysis of Sec23/24 and they all shed
The vesicle is now uncoated

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17
Q

T/F:

Mannose 6 Phosphate is a post translational modification on the golgi that tells the cell is needs to be taken to the ER

A

False

tells the cell it needs to be taken to the lysosome

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18
Q

Which protein coat mediates transport from the trans golgi to the membrane/lumen of lysosomes?

A

Clathrin

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19
Q

What is the structure of clathrin?

A

3 heavy chains, 3 light chains

Sits on top of a coat of adaptor proteins

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20
Q

T/F:

Clathrin coat provides an intrinsic curvature to the membrane

A

True

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21
Q

What do the adaptor proteins bind to?

A

Bind to cargo receptors

clathrin then binds to the adaptor proteins themselves

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22
Q

What is the role of dynamin?

A

Assembles into a ring and pinches off the two membranes

Occurs due to GTP hydrolysis

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23
Q

Rab protein is involved in docking vesicles to ______

A

the plasma membrane

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24
Q

Rab protein is tethered to the membrane by a _____ and recognises its ______ on the target membrane

A

Rab protein is tethered to the membrane by a lipid anchor and recognises its effector complex on the target membrane

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25
Q

Which two proteins make up the t-snare?

A

Syntaxin and SNAP-25

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26
Q

What structure does the SNARE complex make?

A

A stable coiled coil

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27
Q

How does the SNARE complex dissociate so it can be reused?

A

NSF binds to the SNARE complex

ATP is hyrolysed

28
Q

What type of bonds can be seen in the SNARE complex?

A

Noncovalent interactions
2 from SNAP25
1 from synaxtin
1 from VAMP

29
Q

Why is the coiled coil structure of the SNARE complex so stable?

A

They bury the hydrophobic residues really well

also because of the heptad repeat on each of the three proteins

30
Q

T/F:

Dyneins mediate anterograde transport and kinesins mediate retrograde transport

A

False

other way round

31
Q

Alpha tubulin binds _______ GTP

A

Non-exchangeable

32
Q

T/F:

Alpha can be found at the start of the negative end of microtubules

A

True

33
Q

What do kinesins use to walk along microtubules?

A

ATP hydrolysis

34
Q

List four things that might occur to a protein when travelling through the ER

A

Glycosylation
Disulfide bones
Folding
Quality control

35
Q

T/F:

Glycosylation involves the covalent addition and processing of sugars

A

False

Carbohydrates

36
Q

Which reside is involved in the creation of disulfide bonds?

A

Covalent links between cysteine residues to form cystine

37
Q

T/F:

Quality control is specific proteolytic cleavages

A

True

38
Q

What is the role of Oxidised PDI?

A

It recognises reduced cysteins and forms the di sulfide bonds

Can also rearrange disulfide bonds already made

39
Q

What is the role of BIP?

A

Binds to proteins in the ER and prevents them from folding

40
Q

What is the role of Oligosaccharyl transferase?

A

Brings sugars into the ER lumen

41
Q

List the names of the 5 structures of the golgi apparatus from ER to release

A

Cis Golgi network

Cis cisterna
Medial cisterna
Trans cisterna

Trans golgi netowrk

42
Q

What occurs in the cis Golgi network?

A

Phosphorylation of oligosaccharides on lysosomal proteins

recognising Mannose 6 phosphate (signal to go to the lysosome)

43
Q

T/F:

Removal of mannose 6 phosphate occurs in the trans cisterna

A

False

occurs in cis cisterna (and medial cisterna)

44
Q

What occurs in the medial cisterna?

A

Removal of mannose 6 phosphate and addition of GlcNAc

45
Q

What occurs in the trans golgi network?

A

Sulfation of tyrosines and carbohydrates

46
Q

What is the role of the perioxisome?

A

Allows completely folded proteins to move into organelles

47
Q

What sequence would be found at the extreme C terminus of proteins destined for the perioxisome?

A

Ser-Lys-Leu

48
Q

What state do mitochondria have to be in for the uptake of proteins into their matrix (lumen) to occur?

A

They must be energised (with ATP)

In this state they are active

49
Q

Why does the mitochondria have to be energised to allow proteins to enter its matrix?

A

When it is energised, their is an action potential
Voltage gated channels like Tim23 need an action potential to allow them to open

The action potential helps to drag the positively charged leader sequence through the pore (the matrix has a higher pH and more negative charges)

50
Q

Which membrane of the mitochondria is Tom20/22 located?

A

Outer membrane

Brings things from the cytosol into the mitochondria

51
Q

What are the two ways proteins can move to the intermembrane space?

A

Inserted into the inner membrane and then cleaved

Or directly put into the intermembrane space

52
Q

Where can you find the Toc and Tic complex?

A

Toc complex= outer membrane of chloroplast

Tic complex= inner membrane of chloroplast

53
Q

What does the Chloroplast SRP receptor do?

A

Brinds proteins into the thylakoid membrane

54
Q

T/F:

Peroxisomes have two membranes

A

False

Single membrane

55
Q

Which genes encode peoxisomal proteins?

A

All encoded by nuclear genes

56
Q

What do the enzymes in perioxisomes use?

A

They use oxygen to oxidise various substrates

57
Q

What product is generated as a by product by enzymes in the perioxisome?

A

Hydrogen peroxide

58
Q

Which enzyme removes hydrogen peroxide and what does it turn it into?

A

Catalase removes it

Converts it into water

59
Q

Which receptor recognises the peroxisomal targeting sequence?

A

Pex5

60
Q

T/F:

Pex5 with bound protein interacts with Pex8 in the peroxisome

A

False

interacts with pex14

61
Q

Which membrane proteins in the peroxisome allow the protein to be transfered into the lumen?

A

Pex2, Pex10, Pex12

62
Q

What is seen when you have deficienies in Pex12?

A

Catalase is unable to enter the peroxisome

PMP70 is normal

63
Q

What happens when you are Pex3 deficient?

A

Peroxisomal membranes don’t assemble

Both catalase and PMP70 remain in the cytosol

64
Q

What are the two ways proteins can be degraded or recycled?

A
  1. Cytoplasmic degradation by proteosomes using the ubiquination pathway
  2. Proteolysis in lysosomes
65
Q

T/F:

Lysosomes maintain a low pH by pumping protons from the inside to outside

A

False

They pump protons from outside to inside

66
Q

What powers the proton pumps in lysosomes?

A

ATP hydrolysis

67
Q

Enzymes needed to degrade proteins in the lysosome are tagged with _____

A

Mannose 6 phosphate

BCMB2002 (9 decks)

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