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Biochemistry > L10 > Flashcards

L10 Flashcards

(80 cards)

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1
Q

Digestive enzymes, Preprohormones, protein splicing what examples of protein modifications

A

Cleavage

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2
Q

Collagen is an Example of What protein modification

A

Hydroxylation

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3
Q

Lysosomal enzymes, Transcription factors Are examples of what type of protein modifications

A

Phosphorylation

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4
Q

Membrane, Secretory proteins Are examples of what type of protein modifications

A

Glycosylation

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5
Q

lipoproteins Are example of what types of protein modifications

A

Lipidation

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6
Q

Histone Proteins are example of what type of protein modifications

A

Acetylation

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7
Q

%?

Phosphorylation
Glycosylation
Acetylation

A

> 30%
50%
80-90%

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8
Q

Category 1 proteins are ___while category 2 proteins are ___

A

Post translation
Co-translation

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9
Q

Why are C2 proteins co-transnational

A

Because their modification is continued in the golgi

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10
Q

When do proteins become active

A

After modifications

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11
Q

What sends a protein to its target site

A

Ts

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12
Q

Specific modifications in some proteins help in achieving

A

Proper folding
Stability
Activity

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13
Q

Proteins are placed in two main categories based on

A

Location and target

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14
Q

In this category, Synthesisstartsonthefreeribosomes, but complete in the rough ER

A

C2

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15
Q

In this category, Synthesis starts and completes in the ribosomes

A

C1

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16
Q

In c1, this TS is cleaved

A

Mitochondrial TS

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17
Q

This protein has nonTs

A

Cytosol

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18
Q

If TS of C1 is lost due to mutation —>
If TS of c1 is cleaved —>

A

Cytoplasm
Normalm

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19
Q

When do proteins of C1 reach their site?

A

Post-synthesis

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20
Q

Translocation of c1 proteins require

A

Chaperons and receptors

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21
Q

What is the job of chaperons ?

A

Protect protein
Translocation

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22
Q

Ts of Mitochondrial proteins is in which terminal?

A

N

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23
Q

What is the mechanism of mitochondrial proteins

A

1-proteins are unfolded and binds with Chapiron HSP70 and receptors on the mitochondrial membrane

2-This binding leads to h opening of
mitochondrial membrane channels
through which these proteins moved
into the matrix

3-After reaching the matrix, the TS is
cleaved, protein folds & becomes active

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24
Q

Smaller proteins can ___ through nuclear pores / channels

Larger proteins are imported through the nuclear pores in an___ manner

A

diffuse freely

energy dependent

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25
What do nuclear proteins require to move through nuclear channels?
Selective receptors
26
Nuclear proteins have Ts at the
N terminal
27
Which type of peroxisomal proteins are translocated
Folded
28
Peroxisomal proteins have ts at
Skf- c terminal
29
What does Peroxisomal proteins require for their translocation
Binding proteins and receptors
30
Why must ribosomes couple to rER?
1-Ribosomes do not have modifying enzymes Modifying enzymes are present in the rER & Golgi Therefore, ribosomes must couple to rER
31
Which signal is used to couple?
Signal peptide
32
Which ribosomes are attached to to rER?
Only those who synthesize proteins having N-terminal signal peptide
33
A signal peptide (SP) is present as an___ sequence in a protein
N-terminal
34
T/F: SP is not consensus
T
35
The middle sequence of the SP is (hydrophobic or hydrophilic)
hydrophobic
36
Note :The only part which is consnesus is the middle part, all are hydrophobic
37
What is the mechanism of coupling to rER?
Sp +SRP (6proteins+mRNA) = arrest translation?( prevent wrong folding) + binf to SRP on ER. SRP then hydrolize GTP, dissociates from receptor
38
SP is not present in some mature proteins why?
In some cases, the ‘SP’ is cleaved in the ER by signal peptidase
39
ER membrane has 2 types of receptors what are they
Ribosomal SRP
40
Are part of the ER membrane
Integral membrane proteins
41
Require to topogenic and anchor sequence for their crossing and anchoring to the lipid layer
Integral membrane proteins
42
Integral membrane proteins Require topogenic and anchor sequence why?
for their crossing and anchoring to the lipid layer
43
Which proteins are glycosylated or modified
only the intracellular epitose
44
What are the five types of modifications that occurs in the rough ER
Formation of disulfide bond N- linked glycosylation Folding of proteins quality control oligomerization
45
Disulfide bonds are important for __ They may be formed in __or__
Protein folding Intra-chain / interchain #Inter-chain = 2 different proteins = oligomerization
46
Disulfide bond formation is catalyzed by
glutathione oxidase
47
In Protein glycosylation ___ carbohydrates selectively added to certain amino acids in a polypeptide
Complex
48
N-linked glycosylation occurs at the ___group in__
NH2 group Asn
49
O-linked Glycosylation occurs at the group __in__
Oh Ser, thr
50
Where does N-linked glycosylation occur? And why
ER. Because the enzymes needed for modifications are only present in the ER there are no enzymes for modifications in the ribosomes
51
Whre does N-linked glycosylation start and end
Start er End golgi
52
The part of glycosylation that completes in the Golgi is also known as
terminal glycosylation
53
Where is the carbohydrate attached in the protein? 
NH2 group Why you ask, because its N-linked glycosylation
54
Not every amino acid will be glycosylated. What is the condition that must be satisfied for Glycosylation to occur
Asn-x-ser-thr
55
primary proteins are susceptible to form wrong protein-protein interactions & aggregations in RER why?
Because of the high number of proteins density present
56
How to avoid wrong protein protein interactions in the rough ER
By chaperones
57
Mention the eight chaperones
HSP: 40 60 70 90 100 bip calnexin Careticulin
58
prevent incorrect folding, denaturation & aggregation
Chaperones
59
bind to the exposed hydrophobic aa
Chaperones
60
have ATPase activity
Chaperoned
61
Quality control check occurs in
rER
62
T/F: only the correctly folded proteins are allowed to move from rER to the Golgi for their final processing
T
63
Mis-folded proteins cannot move to the Golgi they are degraded in__
proteasomes
64
Protein trafficking, which is ___occurs via ___
Movement of proteins from ER to Golgi Bound globular vesicles
65
What is the sensor that recognizes an incorrectly folded protein
GT
66
Explain the mechanism of quality control
1-GT 👀 wrong protein , adds G 2-Calnexin (chaperone) captures proteins and folds it 3-G II 👀 protein —G
67
This enzymes recognizes a folded proteins with glucose
G II
68
This enzyme captures an unfolded protein with glucose
Calnexin
69
Mention 3 Types of protein modifications in Golgi
Terminal glycosylation (N completes) O-linked glycosylation ( starts and complete in the Golgi apparatus) Sorting/packaging (from trans)
70
O-linked glycosylation Occurs at which structure of the protein
Primary
71
Explain the lysosomal proteins sorting mechanism
1-Lysosomal proteins carry M6P —> to bind and sort proteins by MP6R - Protein + MP6R 2-MP6 ❌MP6R in endosome —> acidic 3-MP6 -Phosphate 4- M6PR recycled to the Golgi as a major pathway 5-MPR recycled to the PM in a minor pathway
72
What sequence does ER protein have and where is it
KEDL at c terminal
73
Why is a KEDLE sequence required for ER proteins
for their retention by rough ER in case of wrong escape to the Golgi
74
Slide 33 and 32 add them here
75
Require special modification (integral membrane proteins /membrane proteins)
Membrane proteins
76
Note: Membrane proteins are glycosylated which faces the lumen ER, Golgi & vesicle Upon targeting the glycosylated part becomes extracellular
77
In the membrane bound proteins the modified part is facing__
Anteriorly Towards the lumen ER, Golgi and vesicles
78
Which proteins have signals and which do not
Secretory proteins have no signals proteins that will function inside the cells need signals
79
Which proteins will be modified membrane proteins or integral proteins?
Membrane proteins
80
What makes intracellular epitose special Compared to others
They are glycosylated or modified

Biochemistry (9 decks)

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