Week 8

Question 1

T/F:

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

Answer 1

True

Question 2

The inner nuclear membrane separates the ___ from the ___

Answer 2

Nucleoplasm from the ER lumen

Question 3

The outer nuclear membrane separates the ___ from the ____

Answer 3

ER lumen from the cytoplasm

Question 4

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

Answer 4

Bound by carrier proteins

Question 5

T/F:

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

Answer 5

False

free ribosomes in the cytoplasm

Question 6

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

Answer 6

Nucleoporins

Question 7

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

Answer 7

The nuclear lamina

Question 8

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

Answer 8

8

Question 9

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

Answer 9

A matrix of FG repeats in the central channel

Question 10

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

Answer 10

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

Question 11

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

Answer 11

Ions, small metabolites and proteins of less than 40kDa

Question 12

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

Answer 12

Lots of basic residues

Question 13

What two basic residues are often seen in the NLS?

Answer 13

Lysine and Arginine

Question 14

T/F:

The NLS signal is required to bring things into the nucleus

Answer 14

True

Question 15

Which protein initially binds the cargo destined for the nucleus?

Answer 15

Importin

Question 16

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

Answer 16

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

Question 17

T/F:

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

Answer 17

False
Interaction with Ran-GTP

Causes a conformational change and the cargo can be released

Question 18

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

Answer 18

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

Question 19

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

Answer 19

They contain a leucine rich export signal

It has a specific spacing of hydrophobic residues

Question 20

T/F:

Proteins to be imported into the nucleus are positively charged

Answer 20

True

Importin recognises basic residues

Question 21

T/F:

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

Answer 21

True

Question 22

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

Answer 22

Ran-GTP and exportin

They form a triple complex

Question 23

How is Ran-GTP converted into Ran-GDP?

Answer 23

Interacts with GAP to become Ran-GDP

Causes a conformation change and the cargo is released

Question 24

Increase in blood glucose levels causes what?

Answer 24

Stimulates pancreatic beta cells to secrete insulin

Question 25

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

Answer 25

True

Question 26

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

Answer 26

GLUT4 is translocated to the plasma membrane to collect the glucose Adipocytes differentiate and have the ability to store glucose

Question 27

T/F: | Insulin is one chain

Answer 27

False | Two chains with cystine bonds

Question 28

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

Answer 28

Potassium leaves and calcium enters

Question 29

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

Answer 29

True

Question 30

T/F: | When insulin levels drop, glut4 receptors will be found on the plasma membrane

Answer 30

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

Question 31

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

Answer 31

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

Question 32

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

Answer 32

Catalytic domain inside the cell

Question 33

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

Answer 33

one receptor phosphorylates Tyr resides on the other receptor