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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
Which two proteins make up the t-snare?
Syntaxin and SNAP-25
26
What structure does the SNARE complex make?
A stable coiled coil
27
How does the SNARE complex dissociate so it can be reused?
NSF binds to the SNARE complex | ATP is hyrolysed
28
What type of bonds can be seen in the SNARE complex?
Noncovalent interactions 2 from SNAP25 1 from synaxtin 1 from VAMP
29
Why is the coiled coil structure of the SNARE complex so stable?
They bury the hydrophobic residues really well | also because of the heptad repeat on each of the three proteins
30
T/F: | Dyneins mediate anterograde transport and kinesins mediate retrograde transport
False | other way round
31
Alpha tubulin binds _______ GTP
Non-exchangeable
32
T/F: | Alpha can be found at the start of the negative end of microtubules
True
33
What do kinesins use to walk along microtubules?
ATP hydrolysis
34
List four things that might occur to a protein when travelling through the ER
Glycosylation Disulfide bones Folding Quality control
35
T/F: | Glycosylation involves the covalent addition and processing of sugars
False | Carbohydrates
36
Which reside is involved in the creation of disulfide bonds?
Covalent links between cysteine residues to form cystine
37
T/F: | Quality control is specific proteolytic cleavages
True
38
What is the role of Oxidised PDI?
It recognises reduced cysteins and forms the di sulfide bonds Can also rearrange disulfide bonds already made
39
What is the role of BIP?
Binds to proteins in the ER and prevents them from folding
40
What is the role of Oligosaccharyl transferase?
Brings sugars into the ER lumen
41
List the names of the 5 structures of the golgi apparatus from ER to release
Cis Golgi network Cis cisterna Medial cisterna Trans cisterna Trans golgi netowrk
42
What occurs in the cis Golgi network?
Phosphorylation of oligosaccharides on lysosomal proteins recognising Mannose 6 phosphate (signal to go to the lysosome)
43
T/F: | Removal of mannose 6 phosphate occurs in the trans cisterna
False | occurs in cis cisterna (and medial cisterna)
44
What occurs in the medial cisterna?
Removal of mannose 6 phosphate and addition of GlcNAc
45
What occurs in the trans golgi network?
Sulfation of tyrosines and carbohydrates
46
What is the role of the perioxisome?
Allows completely folded proteins to move into organelles
47
What sequence would be found at the extreme C terminus of proteins destined for the perioxisome?
Ser-Lys-Leu
48
What state do mitochondria have to be in for the uptake of proteins into their matrix (lumen) to occur?
They must be energised (with ATP) In this state they are active
49
Why does the mitochondria have to be energised to allow proteins to enter its matrix?
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
Which membrane of the mitochondria is Tom20/22 located?
Outer membrane | Brings things from the cytosol into the mitochondria
51
What are the two ways proteins can move to the intermembrane space?
Inserted into the inner membrane and then cleaved Or directly put into the intermembrane space
52
Where can you find the Toc and Tic complex?
Toc complex= outer membrane of chloroplast Tic complex= inner membrane of chloroplast
53
What does the Chloroplast SRP receptor do?
Brinds proteins into the thylakoid membrane
54
T/F: | Peroxisomes have two membranes
False | Single membrane
55
Which genes encode peoxisomal proteins?
All encoded by nuclear genes
56
What do the enzymes in perioxisomes use?
They use oxygen to oxidise various substrates
57
What product is generated as a by product by enzymes in the perioxisome?
Hydrogen peroxide
58
Which enzyme removes hydrogen peroxide and what does it turn it into?
Catalase removes it | Converts it into water
59
Which receptor recognises the peroxisomal targeting sequence?
Pex5
60
T/F: | Pex5 with bound protein interacts with Pex8 in the peroxisome
False | interacts with pex14
61
Which membrane proteins in the peroxisome allow the protein to be transfered into the lumen?
Pex2, Pex10, Pex12
62
What is seen when you have deficienies in Pex12?
Catalase is unable to enter the peroxisome | PMP70 is normal
63
What happens when you are Pex3 deficient?
Peroxisomal membranes don't assemble | Both catalase and PMP70 remain in the cytosol
64
What are the two ways proteins can be degraded or recycled?
1. Cytoplasmic degradation by proteosomes using the ubiquination pathway 2. Proteolysis in lysosomes
65
T/F: | Lysosomes maintain a low pH by pumping protons from the inside to outside
False | They pump protons from outside to inside
66
What powers the proton pumps in lysosomes?
ATP hydrolysis
67
Enzymes needed to degrade proteins in the lysosome are tagged with _____
Mannose 6 phosphate

BCMB2002 (9 decks)

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