Cells F211

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  • Created by: sophie
  • Created on: 30-12-12 13:20


Resolution and magnification....

Light microscope:    200nm        x1,500

TEM:    0.1nm        x500,000

SEM:   0.1nm        x100,000

Magnification: is the degree to which the size of an image is larger than the actual size.

Resolution: is the degree to which it is possible to distinguish between two objects that are very close and see detail.

Staining samples for use in light and electron microscopy;

  • Most biological material inside a cell isn’t coloured, so it can be difficult to distinguish between different features.
  • Coloured stains are used to stain specimens for use with the light microscope. Chemicals which bind to other chemicals on, or in, the specimen, that allow the specimen be to seen. Some chemicals bind to specific structures, such as Acetic orcein staining DNA red.
  • Electron micrographs start off black and white, with the colour being added by a specialised computer program afterwards.

Calculating magnification:

Image size =Actual size x Magnification       I / A x M      

Interpreting photographs and structures of eukaryotic cells under an electron microscope:

Nucleus: Largest organelle, contains genetic info in DNA and the instructions for protein synthesis.

Nucleolus: Dense, spherical structure inside nucleus, production of ribosomes and RNA which pass into the cytoplasm and are used in protein synthesis.

Nuclear envelope: Surrounds the nucleus, studded with pores for commiunication with cytoplasm

Rough endoplasmic reticulum (RER): Continuous with the nuclear envelope. RER is studded with ribosomes,transports proteins to GA.

Smooth endoplasmic reticulum (SER): Continuous with the nuclear envelope but has no ribosomes, makes fats, phospholipids and cholesterol.

Golgi apparatus: Stack of membrane-bound flattened sacs, final modification and packaging into golgi veisicles for secretion.

Ribosomes: Tiny. Some are free in the cytoplasm and some are bound to the RER, amino acids assembled to make proteins.

Mitochondria: Spherical, Double membrane, highly folded internal membrane forms cristae... large SA for enzymes. Aaerobic respiration, where ATP is made.

Lysosomes: Spherical sacs. Single membrane. contain enzymes that are used to break down material.

Chloroplasts: Only in plant cells. Two membranes. Contain grana (stacks of


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