Proteins and Enzymes

Amino acids to proteins
1. Proteins are polymers; they are built up in cells when monomers called amino acids join together end to end
  1. Despite the fact that only 20 different naturally occurring amino acids exist, each protein molecule has hundreds, or even thousands, of amino acids joined together to make a unique sequence giving each protein its own individual properties
    1. The long chains of amino acids fold to give each type of protein molecule a specific shape
      1. Proteins can act as: structural components of tissues (such as muscles), Hormones (such as insulin), Antibodies (part of the body's immune system) and Biological catalysts (known as enzymes)
        The particular shape that a protein molecule has allows other molecules to fit into it- which is particularly important for antibodies and enzymes
How enzymes work
1. Enzymes are substances that increase the rate of chemical reactions without being used up- biological catalysts
  1. Enzymes are proteins folded into complex shapes that allow smaller molecules to fit into them
    1. The place where substrate molecules fit is called the active site
      1. If the shape of the enzyme changes, its active site may no longer work- the enzyme has been denatured
        Enzymes are denatured as a result of high temperatures or extreme pH levels
Temperature, pH and enzymes
1. Temperature
  1. As temperature increases so does the rate of reaction but to high temperatures denature enzymes
    1. The optimum temperature for enzyme activity is 37ºC (body temperature) ; beyond this temperature, the rate of reaction starts to fall rapidly because the enzyme denatures
2. Enzymes also have an optimal pH level depending on where the enzyme works
  1. For example, intestinal enzymes have an optimum pH of about 7.5 whereas enzymes in the stomach work best at about 2
Digestive enzymes
1. The enzymes involved in respiration, photosynthesis and protein synthesis work inside cells whereas other enzymes are produced by specialised cells and released from them; digestive enzymes are like this
  1. They pass out into the gut, where they catalyse the breakdown of food molecules
    1. Different enzymes catalyse different digestion reactions
      1. Amylase breaks starch down into sugars in the salivary glands, pancreas and small intestine
      2. Protease is secreted in the stomach, pancreas and small intestine to break down proteins into amino acids
      3. Lipase is secreted in the pancreas and small intestine to break down lipids (fats) into fatty acids and glycerol
Other digestive substances
1. Stomach acid (hydrochloric acid) helps to begin digestion and kills many harmful micro-organisms that might have been swallowed with food
  1. For this reason, enzymes in this stomach work best at low pH levels
2. Bile is produced by the liver (and stored in the gall bladder) and secreted into the duodenum to neutralise food coming from the stomach so that it doesn't harm the small intestine and because the enzymes in the small intestine work best in alkaline conditions
Uses of enzymes
1. Enzymes allow certain industrial processes to be carried out at normal temperatures and pressures, eliminating the need for expensive equipment and reducing the amount of energy needed
  1. Enzymes are also used in the home, for example, in biological detergents
    1. Protease can be used to pre-digest proteins during the manufacturing of baby foods
    2. Lipase in cooperation with protease can be used in biological detergents to break down substances in stains into smaller, water soluble substances
    3. Carbohydrase can be used to convert starch syrup, which is relatively cheap, into sugar syrup which is more valuable
    4. Isomerase is used to convert glucose syrup into fructose syrup which is sweeter so it can be used in smaller amounts in slimming foods

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Proteins and Enzymes

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	Created by seth.bragg almost 11 years ago