chp3; chemical reactions

• Proteins are organic compounds made up of many amino acids. Enzymes influence metabolism by controlling the chemical reactions in the body
• Inorganic compounds are not based on a carbon chain. Most do not contain carbon atoms at all, but those that do, such as carbon dioxide, are small molecules
• Minerals are important for metabolism because they may be a part of enzymes, may function as cofactors for enzymes, or may be a part of substances such as adenosine triphosphate (ATP) that are involved in metabolism
• Each protein has a characteristic shape due to the folding of the chain
• Each lipid molecule consists of one molecule of glycerol and one, two, or three fatty acid molecules
• Lipids include fats and oil and are another important energy source. They are broken down to fatty acids and glycerol
• Water is important in metabolism because it is the fluid in which other substances are dissolved
• DNA is the genetic material in the nucleus that stores inherited information
• RNA molecule


  Carries information from the DNA in the nucleus to parts of the cell where proteins are made
• Proteins consist of 100 or more amino acids; their type and order are determined by the DNA that codes for the protein's production
• Polysaccharides are larger carbohydrate molecules formed when many simple sugars join together. Glycogen, cellulose, and starch are examples of polysaccharides
• Important inorganic compounds

  • Water
  • Minerals
  • Vitamins
• Amino acid


  A molecule that contains both an amino group and a carboxylic acid group
• Vitamins act as coenzymes for many of the chemical reactions of metabolism
• Organic compounds

  Molecules with a carbon chain, containing hydrogen, and may include oxygen, nitrogen, and sulfur
• Metabolism

  1. Consists of catabolic and anabolic reactions

  2. Catabolic metabolism involves breaking down large molecules to smaller ones (catabolism)

  3. Anabolic metabolism involves building up small molecules into larger ones (anabolism)

  4. Catabolic reactions release energy, anabolic reactions require energy

  5. Concerned with maintaining a balance between energy release and energy utilisation
• Disaccharides

  • Sucrose
  • Maltose
  • Lactose
• Nutrients

  • Water
  • Carbohydrates
  • Lipids
  • Proteins
  • Minerals
  • Vitamins
• Simple sugars join together to form larger molecules; disaccharides are formed when two simple sugars join together
• Carbohydrates


  • Always contain carbon, hydrogen, and oxygen
  • Twice as many hydrogen atoms as oxygen atoms
  • Main source of energy for cells
• Nutrient


  Any substance in food used for growth, repair, or maintaining the body
• Lipids

  • Include cholesterol and the sex hormones
  • Consist of one molecule of glycerol and one, two, or three fatty acid molecules
  • Most common fat is triglyceride, composed of glycerol and three fatty acid molecules
• Monosaccharides

  • Glucose
  • Fructose
  • Galactose
• Enzyme activity

  • Dependent on the shape and availability of the active site, influenced by temperature, pH, substrate and enzyme concentration, removal of products, and presence of cofactors, coenzymes, and enzyme inhibitors
• Coenzymes


  Non-protein organic molecules that act as cofactors for enzymes
• Inhibitors may be used by cells to control reactions and produce products in specific amounts
• Continuous removal of products is necessary to maintain the reaction rate
• Temperature influences enzyme activity, with most reactions increasing in rate as temperature rises within a limited range
• The higher the concentration of enzyme, the faster the rate of a chemical reaction
• Many vitamins


  • Function as coenzymes
• Penicillin


  • Is an enzyme inhibitor that inhibits an enzyme in bacteria involved in cell wall construction
• Increasing substrate concentration increases the rate of reaction until all active sites on enzyme molecules are fully occupied
• Enzyme denaturation

  Occurs at high temperatures, changing the shape of the enzyme and rendering it inactive
• Enzyme inhibitors are substances that slow or stop enzyme activity
• Cofactors


  Substances required by many enzymes to catalyze a reaction, changing the shape of the active site
• Enzymes are sensitive to pH, with each enzyme having an optimum pH for effective function
• Induced-fit model

  When the enzyme and substrate join, weak bonds cause the enzyme's shape to change, creating complementary shapes
• Lock-and-key model

  The shape of the enzyme is complementary to the shape of the substrate, fitting exactly to form the enzyme-substrate complex
• Catalysts decrease the energy needed to break bonds, lowering activation energy and increasing the rate of reaction without being consumed
• In living things, catalysts are proteins called enzymes, allowing chemical reactions to occur at a fast rate at body temperature