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Cell Biology > Protein Sorting And Trafficking > Flashcards

Protein Sorting And Trafficking Flashcards

1
Q

What are the 3 types of transport and name what kind of organelles are involved

A

1- gated transport : nuclear pore complex transport

2- transmembrane : mitochondria, chloroplasts, ER VIA TRANSLOCATORS

3- vesicular - Golgi, endosome, lysosome,

VIA CARGO EXOCYTOSIS AND ENDOCYTOSIS

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2
Q

What allows proteins to be transported to specific organelles due to receptors that bind to it

A

Proteins have a signal sequence of amino acids which bind to receptors for translocation into them

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3
Q

Nuclear localisation contains both import and export signals detected by receptors. What stuff is imported and exported from nucleus

A

Imported - transcription factors / regulators , DNA polymerase, rna polymerase

Exported - mrna , ribosomal rna , trna , Sirna

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4
Q

What on the nuclear pores stop passing of large macromolecules normally such as transcription factors into nucleus

A

Nucleoporin channels

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5
Q

Explain the process of activating transcription of new Tcells from when the Tcell becomes activated

A

NF AT activation causes rise in calcium conc in Tcell activation

This causes calcineurin (calmodulin and calcium complex) to activate phosphatase and this de phosphorylates NF AT

This causes the import signal to be read by receptors

Imported into the nucleus

Transcription of new T cell starts

Kinase then phosphorylates NF AT again and it is exported out of nucleus

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6
Q

Explain the process of insertion of porins into chloroplasts/ mitochondria outer membrane

A

TOM complex (trans located protein) binds to signal sequence

This then translocates it into membrane

Chaperones redirect it to the SAM complex which folds the polypeptide correct

Stays in the membrane

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7
Q

What are chaperones for in formation of porins

A

Prevent aggregation of proteins

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8
Q

What are the events that occur when a protein wants to translocates into the matrix

A

TOM receptor binds to signal sequence

Translocates it through OM

The TIM complex then binds to it causing translocation into the matrix

Signal sequence cleaved

Protein stays there

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9
Q

What enzyme cleaved signal sequences

A

Peptidase

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10
Q

Why is the signal sequence that redirects protein to rer different

A

It stops translation of the polypeptide and is transported to the RER where it binds to a receptor

It it co synthesised at the rer using its ribosomes (peptidyl transferase site)

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11
Q

What happens to soluble proteins at the RER

A

The polypeptide is synthesised fully by the ribosomes

Then polypeptide enters the rer

The signal sequence is cleaved by peptidase and protein STAYS IN RER

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12
Q

How does the rer produce single pass transmembrane proteins

A

The ribosomes finish the polypeptide then it enters

The signal sequence is cleaved and the protein is inserted INTO THE MEMBRANE SINGLE PASS

It can then be glycosylated

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13
Q

How can GPI anchored proteins or even glycoproteins be produced at the rer AND TRANSPORTED TO PLASMA MEMBRANE

A

It takes the transmembrane proteins transmembrane domain and cleaves it

This allows for the GPI anchor to replace it

Vesicular transport then transports it to plasma membrane

(Normal glycoproteins just directed via vesicles)

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14
Q

What is vesicular transport / membrane trafficking important for

A

Phagocytosis / endocytosis

Exocytosis for cell communication/signalling

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15
Q

What are the 3 vesicular pathways

A

1- endocytic (to endosomes and lysosomes)

2- secretory - out to plasma membrane

3- retrieval - from the plasma membrane in

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16
Q

What are the 3 protein coats and where are they found

A

Cop I - found at RER

Cop II found at Golgi cisternae

Clathrin - membrane, endosomes, lysosomes (endocytosis pathway)

17
Q

What are lysosomes / lysozymes

A

Organelles containing acidic / hydrolases enzymes

Degrade endocytosed material

18
Q

How is the acidic ph of lysosomes maintained

A

ATPase H pump

19
Q

Explain the path of endocytosis

A

Vesicle transports to endosomes both early and late

Then produce an endolysosome where degraded

20
Q

Explain the path of phagocytosis (lysosome pathway)

A

Material engulfed/bacteria.

Forms a phagosome

Phagosome forms a phagolysosome with a lysosome

Hydrolysed material

21
Q

What other 2 pathways other than endocytosis and phagocytosis are there in degradation

A

Macropinocytosis- uptake of non specific fluids or material into cell

Autophagy

22
Q

What is autophagy explain it

A

Unwanted proteins or cell debris enclosed by double membrane into an auto phagosome

Fuses with lysosome to form autophagolysosome

Hydrolysis occurs

23
Q

What happens to proteins at the Golgi coming from the rer ?

A

Glycosylation / addition of oligosaccharides

24
Q

What receptor on the trans face of Golgi causes vesicular diversion to the lysosome ?

A

Mannose 5 phosphate receptor

This interacts with proteins glycosylated with it and causes then to move to lysosome

25
Q

What is the constitutive pathway

A

Where budding occurs from Golgi and the new lipids and proteins are exocytosed without a signal needed

26
Q

What is signal mediated exocytosis

A

Signal such as a ligand bound to membrane allows for the vesicular fusion and exocytosis of material from the Golgi

27
Q

Other than get hydrolysed by lysosomes what can endocytosed material do

A

Recycled back into the membrane (eg receptor mediated endocytosis takes back the receptor)
Trans cytosis into another cell

28
Q

How is autophagy important for cellular survival?

A

It can degrade damaged proteins such as aggregated proteins which would mean in functioning cell

29
Q

Are transmembrane proteins produced at the rer soluble or insoluble

A

Insoluble because they are hydrophobic (enter membrane)

- they have hydrophobic side chains like valine

30
Q

How many membranes are in the nuclear pore complex in the nuclear Envelope

A

2

31
Q

What is the difference between Tim 23 and Tim 22

A

Tim 22 inserts the proteins into the inner membrane

Tim 23 the soluble proteins stay inside the matrix

32
Q

Are proteins unfolded or folded when translocated

A

Unfolded

33
Q

Why are proteins produced from the er glycosylated

A

To make sure they fold properly if chaperones allow aggregation or misfolding

Cell Biology (21 decks)

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