GCSE Biology (AQA) B1 - 1.1 & 1.2

Light Microscope:

First developed mid-17th century. Use a beam of light to form image of specimen. Best light microscopes can magnify upto 2000x. Cheap, can be used almost anywhere, magnify live specimens.

Electron Microscope:

Invented - 1930s. Can see subcellular structures. Beam of electrons form an image and can magnify upto 2 000 000x. Transmission electron microscopes give 2D images w/ high resolution + magnification. Scanning electron microscopes give dramatic 3D images w/ lower magnification. Expensive, large, have to be kept at special temperatures.

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Structure and Function:

Nucleus - Controls all activities of cell. Contains genetic material on chromosomes that carry instruction for proteins needed to build new cells/organisms.

Cytoplasm - Liquid gel in which organelles are suspended and where most of the chemical reactions take place.

Cell Membrane - Controls passage of substances into cell, such as --> glucose and minerals. Also controls movemoent of minerals, such as --> Urea and hormones out of the cell.

Mitochondria - Aerobic respiration takes place in them, releasing energy for the cell. They're very small --> 1-2μm in length and 0.2-0.7μm in diameter.

Ribosomes - Protein synthesis takes place here (makes all protein needed in cell).

Structures and Functions:

They have all the structures of a typical animal cell, but they also have extra structures too.

All plant and algal cells have a cell wall which contains cellulose that strengthens the cell and gives support.

Many (but not all) plant cells also have these features:

Chloroplasts - Found in all green parts of a plant. They're green because they contain a green substance called chlorophyll. Chlorophyll absorbs light so the plant can make food by photosynthesis.

Vacuole - Space in cytoplasm that contains cell sap. It keeps the pant cell rigid (support plant).