Organelles - The Nucleus

The Nucleus is the largest organelle, features include:
  - Nuclear Envelope - two membranes with fluid 
     between them
  - Nuclear Pores - holes that go right through the 
     envelope
             - This allows relative large molecules to pass 
                through
  - Nucleolus - a dense, spherical structure




The nucleus contains almost all of the cell's genetic material. The DNA contains instructions for making proteins. Some of these proteins regulate cell activity.
The nucleus also makes RNA and Ribosomes

Linear Magnification

How to calculate the linear magnification of an image:

It may be easier to remember the equation as: AIM or I AM

The magnification is not measured in anything e.g. If the magnification is 1500 just write: x1500

Staining

A lot of biological material is not coloured, and therefore need to be stained in order to view the details of it.

Staining refers to any process that helps to reveal or distinguish different features.

In light microscopy, they may be dyes. In electron microscopy, they are metal particles or metal salts.

Magnification and Resolution

Magnification: The degree to which the size of an image is larger than the object itself

Resolution: The ability to distinguish two objects as distinct from one another. The higher the resolution, the greater detail that can be seen.

Light Microscope
Magnification: x1500
Resolution: 200nm

Transmission Electron Microscope:
Magnification: x500,000
Resolution: 0.1nm

Scanning Electron Microscope:
Magnification: x100,000
Resolution: 0.1nm

Specification: 1.1.1 Cell Structure

- state the resolution and magnification that can be achieved by a light microscope, a 
   transmission electron microscope and a scanning electron microscope
- explain the difference between magnification and resolution
- explain the need for staining samples for use in light microscopy and electron microscopy
- calculate the linear magnification of an image
- describe and interpret drawings and photographs of eukaryotic cells as seen under an 
   electron microscope and be able to recognise the following structures
      - nucleus
      - nucleolus
      - nuclear envelope
      - rough and smooth endoplasmic reticulum
      - golgi apparatus
      - ribosomes
      - mitochondria
      - lysosomes
      - chloroplasts
      - plasma membrane
      - centrioles
      - flagella
      - cilia
            - outline the functions of the structures listed above
- outline the interrelationship between the organelles involved in the production and 
   secretion of proteins
- explain the importance of the cytoskeleton in providing mechanical strength to cells, aiding 
   transport within cells and enabling cell movement
- compare and contrast, with the aid of diagrams and electron micrographs, the structure of 
   prokaryotic cells and eukaryotic cells
- compare and contrast, with the aid of diagrams and electron micrographs, the structure 
   and ultrastructure of plant cells and animal cells