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Biological enzymes

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Biological enzymes Most biological enzymes are 3D globular proteins and perform chemical reactions in cells. An example is haemoglobin, which is needed for the vital carrying on oxygen in blood around to the body from the lungs to the organs that need it. Enzymes serve as Essential Catalysts to virtually every bodily process. An enzyme shortage can cause a variety of illnesses e.g. blue baby syndrome and sickle cell amoeba. Not all proteins are enzymes, but most enzymes are proteins (the exception is catalytic RNA). A catalyst is a molecule, which increases the rate of a reaction but is not the substrate of that reaction and does not get used up in the reaction. A substrate is a molecule upon which an enzyme acts to yield a product. Enzymes convert a substrate molecule into a different molecule. Many of the reactions in catabolism are favourable. This means that these reactions will occur spontaneously even outside of a living organism. But one major problem is, they are too slow to be of any use in a biological system. If cells did not have ways of speeding up catabolism, life would be impossible. In all biological reactions Enzymes accelerate the rate of the reaction. There are enzymes that do specific functions, thus work one certain substrate, such as digestive enzymes are used to break down food molecules and help with digestion, e.g. ...read more.


Each enzyme will take its substrate, convert it to product and hand it off to the next enzyme - analogous to an assembly line. These collections are known as biochemical pathways and are responsible for taking a substrate and converting it into a product. Enzymes are also needed for homeostasis (keeping the internal environment stable, therefore enzymes can work stable. Waste builds up in cells e.g. CO2 and NH3 because ribosome's cannot work properly. Water level decreases, cell becomes flaccid as a result of osmosis. The cell then becomes plasmolysed and hence flaccid. The substrates can be damaged and messed up if other chemicals of different pH are present. The enzymes need the precise pH to work efficiently. A very well known example is pancreas, which needs pH2 for the three digestive enzymes; amylase, lipase and protease, to work essentially and break down the food molecules. Also as product concentration rises the rate at which the reaction occurs will slow. This is known as feedback inhibition. C. Usually biochemical reactions occur in pathways. A biochemical pathway is a chain of reactions in which the products of one reaction become the substrates for the next reaction. Each reaction in a pathway requires the presence of a specific enzyme (or sometimes many enzymes). If any reaction in a pathway does not occur, the product of that pathway will cease to be produced. ...read more.


The vents pump out hot sea water loaded with minerals. Microbes living here do not depend on plants or the sun at all to live, but generate their energy by oxidizing reduced chemicals in the vent plumes and build their cell material from CO2. In fact the reactions that they use to make cell material from CO2 are identical to those used by phototrophs. Follow the link to learn more about hydrothermal vents. There are also independent chemotrophs living in terrestrial environments. Energy Generation Catabolism is all about running reactions to make energy for the cell. Despite the great diversity of life, all organisms on this planet generate their energy using one of three processes. Substrate level Phosphorylation (SLP)- Synthesis of ATP from ADP directly coupled to the breakdown of high energy organic substrates. A high energy phosphate molecule is transferred from the substrate being catabolized to ADP forming ATP. Oxidative or Electron Transport Level Phosphorylation (ETLP) - High energy electrons are removed from the catabolic substrate and given to electron carriers (often NAD or FAD). These carriers eventually transfer their electrons to an electron transport chain which synthesizes ATP using the enzyme ATPase. Eventually the electrons combine with O2 (or some other terminal electron accepter) and H+ to form H20. Photophosphorylation - The conversion of light energy in the form of photons to high energy electrons. These electrons then pass through an analogous electron transport chain as describe under ETLP, eventually resulting in the formation of ATP. ...read more.

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