The Nucleus: Structure, Nuclear Transport (5)

Question 1

nucleus

Answer 1

storage & decoding of genetic info

Question 2

nuclear matrix

Answer 2

PRO containing fibrillary network

where DNA is attached & anchored to the nucleus

Question 3

Nucleolus

Answer 3

granular region, rRNA synthesis & ribosome assembly

Question 4

Nuclear envelope is continuous with ___

Answer 4

endoplasmic reticulum

Question 5

nuclear envelope

Answer 5

2 lipid bilayer membranes

membrane - lumen sac - membrane

Question 6

nuclear lamina

Answer 6

denser layer of intermediate filaments within the inner membrane

composed of lamin PRO

provides structure to the nucleus & is the heterochromatin binding site

Question 7

What part of the nuclear membrane needs to be broken down in mitosis?

Answer 7

nuclear lamina

Question 8

What is the nuclear pore complex composed of?

Answer 8

nucleoporin PROs & cytoplasmic filaments extending into the cytoplasm

Question 9

What is the role of cystolic fibrils?

Answer 9

restrict the entrance of large molecules

Question 10

How do nuclear pores regualte the traffic in & out of the nucleus?

Answer 10

Nuclear localization signal NLS

Question 11

What is an NLS?

Answer 11

positively charged AA sequence added to PRO providing the PRO with access into the nucleus

Question 12

Experiment: What happens when they altered the NLS? & what AA was replaced?

Answer 12

PRO no longer accumulated in the nucleus, accumulated in the cytoplasm

replaced a Lys with Thr (a nonpositively charged AA)

Question 13

Experiment: How did using recombinant DNA techniques with the NLS work? & what did this provide evidence of?

Answer 13

attached NLS to a PRO that normally doesn’t contain NLS, enabling the PRO to enter the nucleus

proved that there are nuclear transport receptors

Question 14

Importins

Answer 14

recognize NLS & bring PROs in

Question 15

Exportins

Answer 15

recognize NES & bring PRO out

Question 16

diffusion

Answer 16

movement of molecules from a region of high concentration to a region of low concentration

Question 17

What are the steps in the mechanism of PRO import through the nuclear PRO complex?

Answer 17

1. NLS attaches to alpha
2. Beta attaches to cytoplasmic filament
3. Move into nucleoplasm (no E consumed)
4. RanGTP attaches to complex, causing the complex to dissociate beta & RanGTP remain bonded, alpha leaves
5. RanGTP & beta move back to cytoplasm (diffusion)
6. Exportin binds to alpha back to nucleus & RanGTP –> RanGDP+phosphate causing beta to be released (Hydrolysis E consuming)
7. Exportin brings alpha into the cytoplasm & RanGDP diffuses back to nucleoplasm
8. RanGDP RanGTP via RCC1 & alpha beta complex reforms

Question 18

RCC1 never ____

Answer 18

goes out of the nucleus

Question 19

RANGAP never ___

Answer 19

goes into the nucleus

Question 20

is GDP –> GTP an energy consuming or producing step?

Answer 20

consuming

Question 21

is GTP –> GDP an energy consuming or producing step?

Answer 21

producing

Question 22

What controls the mechanism of PRO import through the nuclear PRO complex?

Answer 22

GTP to GDP conversion

causing a steep gradient of Ran-GTP across the nuclear membrane

Question 23

Role of RanGAP

Answer 23

maintains low concentration of Ran-GTP in cytoplasm

Question 24

role of RCC1

Answer 24

maintains high concentration of Ran-GTP