Post Translational Modifications, protein Targetting And Collagen Biosynthesis

Question 1

How many helixes are on collagen

Answer 1

3
Every third amino acid would be glycine
Also large amount is Serine and proline

Question 2

Where are the hydrogen bonds and why would then be there

Answer 2

Within the helix structure
Would allow increased stability in the molecule

Question 3

What would be needed for hydroxylation

Answer 3

Vitamins c

Question 4

What does hydroxylation help with

Answer 4

Thermostability

Question 5

What are the two terminals that’s would be found within the procollagen

Answer 5

N terminal
C terminal

Question 6

What terminal would have the disulfide bonds

Answer 6

The C terminal

Question 7

What causes scurvy and what are some of the symptoms

Answer 7

Deficiency of vitamin c or ascortic acid
Weakness, poor healing, gum disease, anaemia

Question 8

What is osteogenesis imperfecta

Answer 8

The mutation in the COL1A1 or COL1A2 genes
Would have glycine substituted for a bulkier amino acid
Not having the correct folding of the molecule

Question 9

What is elders-Danlos syndrome

Answer 9

Stretchy skin
Mutation in the collagen type V or deficiency in the Lysyl oxidase enzymes (not allowing the cores bridges to form)
Would effect the extra cellular cleavage, the cross link formation and stability would be effected

Question 10

What are the steps that would allow the formation of the cross bridges

Answer 10

Lysine residues
Lysyl oxidase and oxygen forming the aldehyde derivatives
Formation of the Aldo’s cross links (thought to be spontaneous)

Question 11

What cleaves the terminals on pro-collagen to form tropocollagen

Answer 11

Collagen peptidase

Question 12

What is needed for collagen to enter the endoplasmic reticulum

Answer 12

The signalling function that would soon be cleaved off (signal pepsidase)

Question 13

What stages would occur I the extracellular

Answer 13

Cleavage of the n and c terminals to for tropocollagen
The formation of the cross bridges

Question 14

How would preproinsulin go to proinsulin

Answer 14

Cleavage of the signalling function
Formation of the disulfide bonds

Question 15

How would proinsulin go to insulin

Answer 15

The cleavage of the C-terminal in the Golgi apparatus

Question 16

What enzyme is used for the formation of the disulfide bonds

Answer 16

Protein disulphide isomerase

Question 17

How can the formation of the disulphide bonds be seen as a redox reaction

Answer 17

At first the substrate would be reduced (contains H+) the enzyme would be oxidised.
When the bond formed the substrate would be oxidised as would lose H+ but the enzyme would be reduced as would gain the H+ from the substrate

Question 18

What happens when a protein is misfolded and why

Answer 18

Move to the cytosol and would be degraded
If not would build, making it toxic
Damage of the ER

Question 19

How would proteins move into the cells from free ribosomes

Answer 19

Signalling element on amino acids (SKL- serine, lysine, leucine)
Attaches to the receptor PTSIR (cytosolic protein receptor)
Would attach to the protein tetramer
Move it to the membrane receptor protein (pex14p)
PTSIR and the tetramer would then move through the membrane
Complex released and the PTSIR moves out (by atp hydrolysis)
Reused

Question 20

How would proteins enter the ER across the membrane

Answer 20

The ribosome would attach to the SRPs (signal receptor proteins) these are GTPS
Attaches to another SRP on the membrane
The ribosome soon released (GTP GOES TO GDP AND PI)
This allows the translocon to open
Signal function cleaved off (signal peptidase)

Question 21

What would change if a protein was being made FOR the membrane

Answer 21

Added a signal anchor transfer sequence

Question 22

What is O-linked glycosylation

Answer 22

Sugar would be added to the OH group of serine of Theronine

Question 23

What is N-linked glycosylation

Answer 23

The sugar would be added to the amino acid (asparagine)

Question 24

What are the four things required for protein sorting

Answer 24

Signalling function
Receptor
Translocation machinery
The energy (ATP)

Question 25

What re the functions of the endoplasmic reticulum

Answer 25

Hydroxylation
Glycosylation
Proper folding of the protein
Insertion of the protein into the membrane
Protein cleavage

Question 26

What can cause protein misfolding

Answer 26

Mutation
Protein incorrectly associated with a subunit
Protein can also get stuck in its misfolded form

Question 27

What are the functions of the chaperones

Answer 27

Monitor the misfolding
Increase transcription of the chaperones
Decrease translation of the protein
Retain the misfolded protein on the ER

Question 28

What is the difference between the Cis face and the Trans face of the Golgi

Answer 28

Cis face is the side closest to the ER and the nucleus
Trans face is the side that is the closest to the membrane of the cell

Question 29

How would the level of C terminal cleaved be different in diabetics

Answer 29

Would be low
Diabetics would not produce their own insulin
So would not have a lot of the cleaving of the C terminal

Question 30

What is the difference between PEX14 and PTS1R

Answer 30

Both would be used for the transport of a protein into the membrane
PEX14 would be the receptor on the perioxisome
PTS1R would be the complex that would recognise the signalling sequence (SKL in the case of catalase) and carry the protein through the membrane

Question 31

What protein does the SKL (serine leucine lysine) sequence refer too

Answer 31

Catalase

Question 32

Why is important glycosylation

Answer 32

Protein stability
Protein folding
Deficiency in N-linked (one the amine of asparagine) would lead to inherited diseases (congenital disorders or glycosylation)
Allows interaction with other proteins

Question 33

Where does N-linked glycosylation happen

Answer 33

In the ER

Question 34

Where does O-linked glycosylation happen

Answer 34

In the golgi

Question 35

What amino acids normally undergo hydroxylation

Answer 35

Lysine and proline (in the ER)
Can form proline hydroxylase