AS BIOLOGY- UNIT 2
The Voice of the Genome-Cell Ultra structure
The 3 basic ideas about cells are:
They are building blocks of structure in living things
Are the smallest units of life
Are derived from other pre-existing cells by division
Contains a blueprint for their growth, development and behaviour
Have sites of chemical reactions of life (metabolism)
Transmission electron microscopy
In the electron microscope (EM), a beam of electrons is used to produce a magnified image. The electron beam is generated by an electron gun and is focused on electromagnets
In transmission electron microscopy of biological material, the electron beam is passed through an extremely thin section of tissue.
Membranes and other structures present in cells are stained with heavy metal ions, making them electron opaque so they stand out
In scanning electron microscopy, the surface of the whole specimen is scanned by a beam of electrons
The 3D image is created from electrons reflected from the surface and also from electrons generated their secondary electrons.
Larger specimens can be viewed by scanning electron microscopy than by transmission electron microscopy, but the reaction is not as great
Eukaryotic cells have a nucleus and prokaotic cells don’t
The ultrastructure of an animal cell
The fluid around the organelles in an eukaryotic cell is called the cytosol which is formed and used in the chemical reactions of life (metabolism which involves the chemical metabolites).
They cytosol and organelles are contained within the plasma membrane, allowing the metabolites to move within the organelles
Introducing organelles
Nucleus- is the largest organelle (10-20µm diameter). It’s surrounded by a double membrane with 100nm pores (diameter) and pores make up 1/3 of the nuclear membrane’s surface diameter. The nucleus contains chromosomes which appear dispersed as a diffuse network (chromatin). The nuclei are present in nucleus (is tiny and rounded and is where...