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Biochemistry > L10 > Flashcards

L10 Flashcards

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
Q

What do nuclear proteins require to move through nuclear channels?

A

Selective receptors

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26
Q

Nuclear proteins have Ts at the

A

N terminal

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27
Q

Which type of peroxisomal proteins are translocated

A

Folded

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28
Q

Peroxisomal proteins have ts at

A

Skf- c terminal

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29
Q

What does Peroxisomal proteins require for their translocation

A

Binding proteins and receptors

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30
Q

Why must ribosomes couple to rER?

A

1-Ribosomes do not have modifying enzymes

Modifying enzymes are present in the rER & Golgi Therefore, ribosomes must couple to rER

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31
Q

Which signal is used to couple?

A

Signal peptide

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32
Q

Which ribosomes are attached to to rER?

A

Only those who synthesize proteins having N-terminal signal peptide

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33
Q

A signal peptide (SP) is present as an___ sequence in a protein

A

N-terminal

34
Q

T/F: SP is not consensus

A

T

35
Q

The middle sequence of the
SP is (hydrophobic or hydrophilic)

A

hydrophobic

36
Q

Note :The only part which is consnesus is the middle part, all are hydrophobic

A
37
Q

What is the mechanism of coupling to rER?

A

Sp +SRP (6proteins+mRNA) = arrest translation?( prevent wrong folding) + binf to SRP on ER.

SRP then hydrolize GTP, dissociates from receptor

38
Q

SP is not present in some mature proteins why?

A

In some cases, the ‘SP’ is cleaved in the ER by signal peptidase

39
Q

ER membrane has 2 types of receptors what are they

A

Ribosomal
SRP

40
Q

Are part of the ER membrane

A

Integral membrane proteins

41
Q

Require to topogenic and anchor sequence for their crossing and anchoring to the lipid layer

A

Integral membrane proteins

42
Q

Integral membrane proteins Require topogenic and anchor sequence why?

A

for their crossing and anchoring to the lipid layer

43
Q

Which proteins are glycosylated or modified

A

only the intracellular epitose

44
Q

What are the five types of modifications that occurs in the rough ER

A

Formation of disulfide bond
N- linked glycosylation
Folding of proteins
quality control
oligomerization

45
Q

Disulfide bonds are important for __
They may be formed in __or__

A

Protein folding
Intra-chain / interchain
#Inter-chain = 2 different proteins = oligomerization

46
Q

Disulfide bond formation is catalyzed by

A

glutathione oxidase

47
Q

In Protein glycosylation ___ carbohydrates selectively added to certain amino acids in a polypeptide

A

Complex

48
Q

N-linked glycosylation occurs at the ___group in__

A

NH2 group
Asn

49
Q

O-linked Glycosylation occurs at the group __in__

A

Oh
Ser, thr

50
Q

Where does N-linked glycosylation occur? And why

A

ER. Because the enzymes needed for modifications are only present in the ER there are no enzymes for modifications in the ribosomes

51
Q

Whre does N-linked glycosylation start and end

A

Start er
End golgi

52
Q

The part of glycosylation that completes in the Golgi is also known as

A

terminal glycosylation

53
Q

Where is the carbohydrate attached in the protein? 

A

NH2 group
Why you ask, because its N-linked glycosylation

54
Q

Not every amino acid will be glycosylated. What is the condition that must be satisfied for Glycosylation to occur

A

Asn-x-ser-thr

55
Q

primary proteins are susceptible to form wrong protein-protein interactions & aggregations in RER why?

A

Because of the high number of proteins density present

56
Q

How to avoid wrong protein protein interactions in the rough ER

A

By chaperones

57
Q

Mention the eight chaperones

A

HSP: 40 60 70 90 100
bip
calnexin
Careticulin

58
Q

prevent incorrect folding, denaturation & aggregation

A

Chaperones

59
Q

bind to the exposed hydrophobic aa

A

Chaperones

60
Q

have ATPase activity

A

Chaperoned

61
Q

Quality control check occurs in

A

rER

62
Q

T/F: only the correctly
folded proteins are allowed to move from rER to the Golgi for their final processing

A

T

63
Q

Mis-folded proteins cannot move to the Golgi they are degraded in__

A

proteasomes

64
Q

Protein trafficking, which is ___occurs via ___

A

Movement of proteins from ER to Golgi
Bound globular vesicles

65
Q

What is the sensor that recognizes an incorrectly folded protein

A

GT

66
Q

Explain the mechanism of quality control

A

1-GT 👀 wrong protein , adds G
2-Calnexin (chaperone) captures proteins and folds it
3-G II 👀 protein —G

67
Q

This enzymes recognizes a folded proteins with glucose

A

G II

68
Q

This enzyme captures an unfolded protein with glucose

A

Calnexin

69
Q

Mention 3 Types of protein modifications in Golgi

A

Terminal glycosylation (N completes)

O-linked glycosylation ( starts and complete in the Golgi apparatus)

Sorting/packaging (from trans)

70
Q

O-linked glycosylation Occurs at which structure of the protein

A

Primary

71
Q

Explain the lysosomal proteins sorting mechanism

A

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
Q

What sequence does ER protein have and where is it

A

KEDL at c terminal

73
Q

Why is a KEDLE sequence required for ER proteins

A

for their retention by rough ER in case of wrong escape to the Golgi

74
Q

Slide 33 and 32 add them here

A
75
Q

Require special modification (integral membrane proteins /membrane proteins)

A

Membrane proteins

76
Q

Note: Membrane proteins are glycosylated which faces the lumen ER, Golgi & vesicle Upon targeting the glycosylated part becomes extracellular

A
77
Q

In the membrane bound proteins the modified part is facing__

A

Anteriorly Towards the lumen ER, Golgi and vesicles

78
Q

Which proteins have signals and which do not

A

Secretory proteins have no signals
proteins that will function inside the cells need signals

79
Q

Which proteins will be modified membrane proteins or integral proteins?

A

Membrane proteins

80
Q

What makes intracellular epitose special Compared to others

A

They are glycosylated or modified

Biochemistry (9 decks)

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