Week 4: Protein Import/Edport Flashcards

1
Q

What happens if the protein is water soluble?

A

Stay in the cytoplasm Go outside the world (secretion) Go to the nucleus Go to other organelles (mitochondria, chloroplasts, peroxisomes)

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2
Q

How is the protein targeted to the membrane?

A

Need carrier to get the protein across the membrane

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3
Q

What is a bacterial system called?

A

TAT (twin arginine translocation)

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4
Q

What does TAT do

A

Take folded proteins across the membrane

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5
Q

What does getting a soluble protein across the membrane mean?

A

Move charged residues through the hydrophobic interior of the membrane

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6
Q

What are some views of the endoplasmic reticulum?

A

1) Immunofluoresence 2) scanning EM 3) transmission ER 4) model

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7
Q

Which resolution is higher than immunofluorescence?

A

Scanning EM

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8
Q

What are ribosomes associated with?

A

MRNA molecules

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9
Q

What are rough ER defined by?

A

The presence of ribosomes bound to cytosolic surface

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10
Q

What does polypeptide chain have?

A

Directionality N terminus and C terminus

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11
Q

What does the secretory protein that contain a signal sequence direct ?

A

Emerging polypeptide and ribosome to the ER membrane

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12
Q

What is a signal hypothesis?

A

The polypeptide moves into cisternal space of the ER through a protein-lined aqueous channel in the ER membrane

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13
Q

What does the single recognition particle in mammals consist of?

A

6 different polypeptides + RNA (7s RNA)

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14
Q

What does the SRP bind?

A

Both the SS on the nascent polypeptide chain and the ribosome

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15
Q

How does the binding to the ER occur?

A

1) SRP and SRP receptor (in the RER) 2) Ribosome and Translocon

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16
Q

How is the SRP released form the ER receptor?

A

SRP-ribosome-nascent-polypeptide binds to the cytosolic surface of the ER membrane

17
Q

What enzyme cleaves the signal peptide?

A

Signal peptidase

18
Q

What helps to fold the protein to pass through the lumen?

A

Chaperon

19
Q

What does targeting to the membrane require?

A

Signal polypeptide ( SRP and SRP receptor)

20
Q

What is required for protein to cross the membrane?

A

Translocon

21
Q

How is crossing the membrane done?

A

Co-translationally (protein crosses the membrane and at the same time it is synthesised)

22
Q

What was the matrix?

A

The cytoplasm of the bacterium

23
Q

What is the function of mitochondria?

A

Encodes and produces it’s own proteins

24
Q

What was the inter membrane space?

A

Periplasm of a gram negative bacterium

25
Q

What do mitochondria and chloroplast have in common?

A

Organelles that originated by endosymbiosis Make their own proteins/ most encoded in the nucleus and synthesised in the cytoplasm

26
Q

What is the difference between mitochondrial system and RER system?

A

There is no co-translational translocation across the membrane

27
Q

What is an example of a chaperone?

A

Hsp50

28
Q

What is the machinery that gets the polypeptide across the outer membrane ?

A

TOM complex

29
Q

What is TIM?

A

A hydrophobic protein channel in the IMM

30
Q

Inside the matrix what does the chaperone interact with ?

A

Polypeptide - helps to pull it through the membrane and then help it fold correctly

31
Q

What removes the presequence?

A

Peptidase

32
Q

What is the Translocon in outer membrane of chloroplast?

A

TOC

33
Q

What is the Translocon in inner membrane?

A

TIC

34
Q

What is stop transferase sequence?

A

Hydrophobic transmembrane segment containing at least 15 amino acids

35
Q

Where is stop transferase sequence located?

A

Remain in the membrane and is not passed through to the lumen

36
Q

What is the role of Translocon?

A

Responsible for determining the correct orientation of the protein in the membrane

37
Q

What orientation is the proteins synthesised in the RER ?

A

Inserted into the lipid bilayer in a predictable orientation determined by its amino acid sequence

38
Q

Where are carbohydrate chain located?

A

Cisternal side of the cytoplasmic membrane which become exoplasmic side of the plasma membrane following the fusion of vesicles with plasma membrane

39
Q

What will be found in the cytoplasm?

A

Glycerol, fatty acid and head group