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BCMB2002 > Week 8 > Flashcards

Week 8 Flashcards

1
Q

T/F:

The nucleus is surrounded by a double membrane that is continuous with the ER

A

True

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2
Q

The inner nuclear membrane separates the ___ from the ___

A

Nucleoplasm from the ER lumen

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3
Q

The outer nuclear membrane separates the ___ from the ____

A

ER lumen from the cytoplasm

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4
Q

Proteins that are destined for the nucleus are bound by what type of proteins?

A

Bound by carrier proteins

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5
Q

T/F:

Proteins destined for the nucleus are translated on free ribosomes on the ER

A

False

free ribosomes in the cytoplasm

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6
Q

What is the name of the proteins that make up the nuclear pore complex?

A

Nucleoporins

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7
Q

What is the membrane portion of the nuclear pore complex attached directly to?

A

The nuclear lamina

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8
Q

How many long filaments extend from the nuclear pore complex and join to form a nuclear basket?

A

8

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9
Q

What is found in the centre of the nuclear pore complex?

A

A matrix of FG repeats in the central channel

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10
Q

What is the role of the hydrophobic FG repeat of the nucleoporin?

A

Phenelalanine and glycine
Recognise what’s being imported into the nucleus
The mesh is pushed aside and the incoming protein can interact with the residues

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11
Q

What molecular weight of ions and small metabolites can pass through the nuclear pore complex passively?

A

Ions, small metabolites and proteins of less than 40kDa

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12
Q

What type of residues does the nuclear localization signal (NLS) contain?

A

Lots of basic residues

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13
Q

What two basic residues are often seen in the NLS?

A

Lysine and Arginine

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14
Q

T/F:

The NLS signal is required to bring things into the nucleus

A

True

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15
Q

Which protein initially binds the cargo destined for the nucleus?

A

Importin

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16
Q

What does the importin molecule interact with in terms of the nuclear pore complex?

A

It binds to a nucleoporin that contains a short hydrophobic sequence (lots of phe and gly repeats)

17
Q

T/F:

Interaction with Ran-GDP allows the importin to release the cargo within the nucleus

A

False
Interaction with Ran-GTP

Causes a conformational change and the cargo can be released

18
Q

How does Ran-GTP then get recycled so it can be used again?

A

Exchanges GDP for GTP in the prescence of the Ran-guanine exchange factor (Ran-GEF) inside the nucleus

Interaction with Ran-GTPase activating protein (Ran-GAP) in the cytoplasm allows the RAN to hydrolyse the GTP and be ready for another cycle

19
Q

What identifies proteins as proteins needed to be EXPORTED from the nucleus?

A

They contain a leucine rich export signal

It has a specific spacing of hydrophobic residues

20
Q

T/F:

Proteins to be imported into the nucleus are positively charged

A

True

Importin recognises basic residues

21
Q

T/F:

Proteins to be exported from the nucleus have hydrophobic residues in their sequence

A

True

22
Q

Which two molecules does the cargo protein needed to be exported out of the nucleus interact with?

A

Ran-GTP and exportin

They form a triple complex

23
Q

How is Ran-GTP converted into Ran-GDP?

A

Interacts with GAP to become Ran-GDP

Causes a conformation change and the cargo is released

24
Q

Increase in blood glucose levels causes what?

A

Stimulates pancreatic beta cells to secrete insulin

25
Q

T/F:

When insulin binds to its receptor, two protein kinase b dependent and independent pathways take place at the same time

A

True

26
Q

When insulin binds to its receptors, what are the two main things that occur next at the same time?

A

GLUT4 is translocated to the plasma membrane to collect the glucose

Adipocytes differentiate and have the ability to store glucose

27
Q

T/F:

Insulin is one chain

A

False

Two chains with cystine bonds

28
Q

What cell trigger allows for vesicles containing insulin to be released from the cell?

A

Potassium leaves and calcium enters

29
Q

T/F:
Glucose being turned into pyruvate in the cell causes the potassium channels to remove potassium from the cell and creates an action potential and therefore calcium fluxes in

A

True

30
Q

T/F:

When insulin levels drop, glut4 receptors will be found on the plasma membrane

A

False

They will be found in vesicles within the cell waiting for blood glucose levels and insulin levels to increase

31
Q

What is the role of the activated proteases in terms of Glut4?

A

They break up TUG into fragments which allows Kinesin to move the vesicle along the microtubule

32
Q

When insulin binds to the extracellular domain of the insulin receptor, what part of the receptor becomes activated?

A

Catalytic domain inside the cell

33
Q

When the catalytic domain of the insulin receptor becomes activated, what does it do?

A

one receptor phosphorylates Tyr resides on the other receptor

BCMB2002 (9 decks)

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