Cell Nucleus

Question 1

What are ribosomes?

Answer 1

Ribosomes carry out translation. The more protein synthesis a cell needs to do, the more ribosomes it has

Question 2

What is the nucleus?

Answer 2

The nucleus contains most of the cells genes and genetic information. It is the cells control centre

Question 3

What is the structure of the nucleus?

Answer 3

Surrounded by nuclear enveloped, has channels called nuclear pores, contains tightly packed DNA, prominent area called nucleolus

Question 4

What is the nuclear envelope?

Answer 4

Composed of two membranes
Each membrane is a phospholipid bilayer
Outer membrane continuous with ER

Question 5

What is nuclear lamina?

Answer 5

Inner surface of nuclear envelope
Composed of intermediate filaments (lamins)
Maintains shape of nucleus
Helps organise the packing of DNA

Question 6

What are nuclear pores?

Answer 6

Channels made of proteins
Spans nuclear envelope
~1000 per cell
Controls movement of molecules out of or into nucleus

Question 7

What moves from Nucleus to Cytoplasm?

Answer 7

mRNA, tRNA and ribosmal subunits move from nucleus to cytoplasm
- mRNA carrie’s information from a gene
- tRNA and ribosomal subunits are needed to build proteins

Question 8

What moves from cytoplasm to nucleus?

Answer 8

Control signals, building materials and energy move from cytoplasm to nucleus
- Tells gene to turn on or off
- Building blocks of RNA
- Energy for chemical synthesis

Question 9

What is the Nucleolus?

Answer 9

A prominent nuclear structure within non-dividing cells.
Non membrane bound specialised region within nucleus
Responsible for making rRNA and ribosomal subunits

Question 10

How is DNA organised in the nucleus?

Answer 10

DNA helix interacts with histones forming a 10mm diameter fibre called a nucleoside. Further interactions cause another fibre to form. During cell division the fibres coil to form metaphase chromosomes

Question 11

What is Euchromatin and Heterochromatin?

Answer 11

Euchromatin is less dense: contains genes being used by that cell
Heterochromatin is more dense: contains genes not being used

Question 12

What is the relationship between euchromatin and heterochromatin?

Answer 12

Dynamic relationship
Transcription machinery needs to access specific DNA regions to begin transcription, euchromatin allows this