Bacteria are a diverse group of ubiquitous micro organisms all of which consist of only a single cell that lacks a distinct nuclear membrane and has a cell wall of a unique composition.
Bacteria are usually classified by means of Gram's stain, whether or not they require oxygen, and on the basis of shape. A bacterial cell may be spherical, rod-like, spiral, comma-shaped, corkscrew-shaped, or filamentous, resembling a fungal cell. The majority of bacteria range in size from 0.5 to 5 mm. Many are motile, bearing flagella, possess an outer slimy capsule, and produce resistant spores. In general bacteria reproduce only asexually, by simple division of cells, but a few groups undergo a form of sexual reproduction. Bacteria are largely responsible for decay and decomposition of organic matter, producing a cycling of such chemicals as carbon, oxygen, nitrogen, and sulphur. A few bacteria obtain their food by means of photosynthesis, some are saprophytes, and others are parasites, causing disease. The symptoms of bacterial infections are produced by toxins. Research Bacteria
Chlorophyll is the green colouring matter of plant leaves and absorbs the light necessary for photosynthesis.
Chlorophyll absorbs mainly red, violet, and blue light and reflects green light. The great abundance of chlorophyll in leaves and its occasional presence in other plant tissues, such as stems, causes these plant parts to appear green. In some leaves, chlorophyll is masked by other pigments.
Chlorophyll is a large molecule composed mostly of carbon and hydrogen. At the centre of the molecule is a single atom of magnesium surrounded by a nitrogen-containing group of atoms called a porphyrin ring. The structure somewhat resembles that of the active constituent of haemoglobin in the blood. A long chain of carbon and hydrogen atoms proceeds from this central core and attaches the chlorophyll molecule to the inner membrane of the chloroplast, the cell organelle in which photosynthesis takes place. As a molecule of chlorophyll absorbs a photon of light, its electrons become excited and move to higher energy levels. This initiates a complex series of chemical reactions in the chloroplast that enables the energy to be stored in chemical bonds. Research Chlorophyll
The lamina is the blade on the leaf on either side of the midrib on flowering plants. It is usually the primary organ of photosynthesis. Research Lamina
The abyssal zone is the region of an ocean between 2000 and 6000 metres deep, lying between the bathyal zone above and the hadal zone below. The abyssal zone is too far from the surface for light to penetrate, and hence too far for photosynthesis to take place. Research Abyssal Zone
A bicarbonate indicator is a PHindicator sensitive enough to show a colour change as the concentration of the gas carbon dioxide increases. The indicator is used in photosynthesis and respiration experiments to find out whether carbon dioxide is being liberated. The initial red colour changes to yellow as the pH becomes more acidic. Carbon dioxide, even in the concentrations found in exhaled air, will dissolve in the indicator to form a weak solution of carbonic acid, which will lower the pH and therefore give the characteristic colour change. Research Bicarbonate Indicator
The Probert Encyclopaedia was designed, edited and programed by
Matt and Leela Probert
Abbreviations
Research Bacteria
