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All living organisms are composed of cells and the division of a living cell forms new cells.
Cells are small so microscopes are needed to see them. The coverslip placed over the specimen on the slide gives a clearer view by reducing the scattering of light as it passes through the slide.
A typical school light microscope will magnify 40, 100 and 400 times. The magnification is calculated by multiplying the power of the objective lens by the power of the eyepiece. Make sure you know the cell structures visible with a light microscope and the differences between an animal and a plant cell.
Centrioles are not in the cells of higher plants but are in animal cells. Animal cells do not have a cell wall, chloroplasts, chromoplasts, leucoplasts or a large central vacuole of cell sap but plant cells do. Both animal and plant cells have an encircling cell membrane (plasmalemma), cytoplasm, nucleus with nucleoplasm, chromatin or chromosomes and nucleoli. Protoplasm is the term used for the living contents of cell bounded by and including the plasmalemma but it does not include the large vacuole of plant cells.
An electron microscope gives much greater magnification (over 500,000 time if required). Many new structures and details became visible - mitochondria and details of its structure, Golgi apparatus, lysosomes, endoplasmic reticulum, ribosomes, nuclear envelope and pores, outline of membrane structure, details of centriole structure.
Cell Membrane (plasmalemma): Fluid-mosaic structure involving a bi-lipid layer with proteins, semi-permeable, keeps cell contents together, controls entry and exit of materials, active transport of specific materials across it.
Cytoplasm: Sticky fluid in which the organelles are suspended, many biochemical processes take place here, e.g., glycolysis.
Nucleus: Contains the hereditary material, DNA - deoxyribonucleic acid, visible as chromatin in active cells and condensed into chromosomes when nucleus undergoing mitosis or meiosis. Our 30,000 different genes are present on the DNA.
Nucleolus: The 'subunits' for ribosome are produced here.
Mitochondria: The aerobic steps of respiration occur here - Krebs cycle in the matrix and oxidative phosphorylation in the cristae, 36 of the 38 ATPs from one molecule of glucose are produced here. The other two are made during glycolysis.
Ribosomes: Made of RNA and protein; specific proteins are made by the ribosomes under 'instructions' from the DNA.
Lysosomes: Tiny sacs of digestive enzymes, role in phagocytosis, recycle worn-out organelles and cells.
Golgi apparatus: Produce lysosomes, export materials including the cellulose for plant cell walls.
Endoplasmic Reticulum (ER): Two kinds rough (RER) with ribosomes on their outer surface and smooth (SER).
RER: Modifies proteins made by the ribosomes on its surface, transport of biochemicals throughout cell.
SER: Formation of lipid and detoxification of dangerous chemicals.
Centrioles: Located in the centrosome a dense region close to nucleus; centrioles assist the formation of spindle fibres during mitosis and meiosis and give the cell the potential to form cilia or flagella.
Chloroplast: Photosynthesis - light phase in the chlorophyll-rich grana, dark phase in stroma.
Leucoplast: Food storage - particularly starch; may store protein and/or lipid.
Chromoplast: Colours petals to attract pollinators and colours fruit to attract seed dispersers.
Large Plant Cell Vacuole: Storage of water, food, waste and assists in the elongation of cells during growth.
Cellulose Cell Wall of Plants: Prevents lysis of plant cells, protects and supports plant cell. The middle lamella of pectin (calcium pectate) glues neighbouring plant cell wall together.
Links
Introduction to the world of cells but plant and animal.
http://micro.magnet.fsu.edu/cells/
A detailed diagram of the animal cell.
http://micro.magnet.fsu.edu/cells/animalcell.html
From the same site but this time dealing with plant cells.
http://micro.magnet.fsu.edu/cells/plantcell.html
Another look at the plant cell.
http://www.biologie.uni-hamburg.de/b-online/e04/04a.htm
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