Nucleus - L10

Question 1

What are ribosomes made of ?

Answer 1

Ribosomal RNA and proteins

Question 2

Two types of ribosomes?

Answer 2

Found attatched to the rough ER

Free ribosomes floating in cytosol

Question 3

What determines the no. of ribosomes made?

Answer 3

More protein synthesis means that more ribosomes are required

Question 4

How big is the nucleus?

Answer 4

5 - 10 µm

Question 5

Does the nucleus have all the genes?

Answer 5

No, it has most. Other genes are found in the mito and chloroplast

Question 6

What are the two things that the nucleus does?

Answer 6

Houses the inheritable DNA and has some control over the cell’s processes

Question 7

What does the nuclear envelope do?

Answer 7

Acts as a barrier to protect the genes inside from damage

Question 8

Nuclear pores fucntion

Answer 8

Allows stuff to pass through

Question 9

Where is the nuclear envelope connected to?

Answer 9

It’s continuous with the ER
The perinuclear space is continuous with the lumen

Question 10

How many membranes is the nuclear envelope?

Answer 10

2 made of phospho bilayers

Question 11

Inner layer of the nuclear envelope lined by what?

Answer 11

Nuclear lamina made of a meshwork of intermediate filaments

Question 12

What does the nuclear lamina do?

Answer 12

The intermediate filaments are strong and rigid so it helps to maintain the structure and shape of the nucleus + in packing the DNA

Question 13

What is a nuclear pore made of?

Answer 13

Multiple proteins called nucleoporins

• It spands both the membranes

Question 14

Term for what moves in and out of the cell through nuclear pores?

Answer 14

Nucleocytoplasmic exchange

Question 15

What moves out of the nucleus via pore?

Answer 15

mRNA, tRNA and ribosomal subunits

Question 16

What moves inside the nucleus via pores?

Answer 16

Chemical signals to turn a gene on or off, building mats for ribosomes and energy for chemical synthesis

Question 17

What is a nucleolus?

Answer 17

A prominent structure when the cell is not dividing

Question 18

Is the nucleolus membrane bound?

Answer 18

No

Question 19

What does the nucleolus do?

Answer 19

Makes the ribosomal RNA and it’s subunits –> transported to cytosol to make the ribosomes

Question 20

What determines how many nucleoli are present?

Answer 20

Stage of the cell cycle, cell type and its species

Question 21

Where are nucleoli found (frog egg reference)

Answer 21

Found in the viable cells to make proteins for the cell

Question 22

What is DNA?

Answer 22

A nucleotide polymer

Question 23

Why is effective packaging of DNA important?

Answer 23

Around 2.5m in each cell, all stretched around the sun 6 times, hence must be packaged and organised well to fit in cell but also accessible.

Question 24

How big is the DNA double helix?

Answer 24

2nm

Question 25

What does the DNA wrap around to form a 10nm diameter form?

Answer 25

Wraps around proteins called histones (H2 - H4)

Question 26

What is an optimum?

Answer 26

8 histones interacting

Question 27

How many times does the DNA wrap around the histone?

Answer 27

1.67 times to form beads called nucleosomes

Question 28

How does DNA go from 10nm - 30nm?

Answer 28

It coils around an H1 histone

Question 29

30 - 300nm?

Answer 29

Coils in a flower shape, found in non-dividing cells.

It supercoils to form metaphase chromosomes during cell division

Question 30

How is DNA screened for defects?

Answer 30

Using a Karyotype

Question 31

During which cell stage are the chromosomes not random?

Answer 31

Interphase

Question 32

Are chromosome pairs usually together when no cell division is occuring?

Answer 32

No

Question 33

What is Euchromatin?

Answer 33

Less dense areas of chromatin meaning that the cell is currently using the genes i.e it is “active” and more easily accessible

Question 34

What is Heterochromatin?

Answer 34

More dense area, genes are currently not being used

Question 35

What kind of relationship between Heterochromatin and Euchromatin?

Answer 35

Dynamic