Metabolism 🥩

• • Catabolic reaction happens when large molecules are broken down into smaller ones.
  • Release energy
  • E.g., digestion
• • Anabolic reaction is when small molecules are built up into larger ones
  • Requires energy
  • E.g., protein synthesis
• Metabolism refers to all the chemical reactions occurring in a living organism.
• A nutrient is any substance in food that provides energy, is essential for growth, or assists in the functioning of the body.
• Nutrients:

  • Water
  • Carbohydrates
  • Lipids
  • Proteins
  • Minerals
  • Vitamins
• Organic compounds are substances that have large molecules and contain carbon, such as carbohydrates, amino acids, proteins, lipids and nucleic acids.
• Monosaccharides are simple sugars

  E.g., glucose, fructose and galactose
• Disaccharides are simple sugars joined together.

  E.g., sucrose, maltose and lactose
• Polysaccharides are larger carbohydrate molecules formed when many simple sugars are joined together.

  E.g., glycogen, cellulose, starch
• An enzyme is an organic substance that increased the speed of chemical changes without being altered or destroyed in the change; an organic catalyst.
• Enzymes lower activation energy by providing a specific shape to fit substrate molecule into active site.
• The rate of reaction increases with temperature until it reaches optimum temperature then decreases again due to denaturation of enzymes.
• The active site is where the reaction takes place.
• A coenzyme is a small non-protein molecule which acts with an enzyme to increase its activity.
• pH affects enzyme activity as they have optimal pH range where they work best.
• Substrates bind to active sites on enzymes which causes conformational change (shape change) so that products can be released from active site.
• Inhibitors are substances that reduce the rate of reaction, either reversibly (competitive) or irreversibly (non-competitive).
• The enzyme-substrate complex is the structure formed when an enzyme and a substrate combine.
• The lock-and-key model states that the shape of the enzyme (the key) is always complementary to the shape of the substrate (the lock). Therefore, the two will fit exactly to form the enzyme-substrate complex.
• The induced-fit model states that when the enzyme and substrate join, they form weak bonds that cause the shape of the enzyme to change, creating complementary shapes.
• Factors affecting enzyme activity:

  • Concentration of the enzyme
  • Substrate concentration
  • Temperature
  • pH levels
  • Cofactors
  • Enzyme inhibitors
• The higher the concentration of enzyme, the faster the rate of a chemical reaction because there are more enzyme molecules to influence reactants.
• Increasing the substrate concentration also increases the rate of reaction. Increasing the substrate beyond a certain concentration will cease to have effect because the active sites on all the enzyme molecules will be fully occupied.
• The products of the reaction must be continually removed, otherwise the rate of reaction will slow because it becomes more difficult for the substrate molecules to make contact with the enzyme molecules.
• The rate of most chemical reactions increases as temperature increases. Beyond about 45-50 degrees their structure changes and they denature. The optimum temperature for most chemical reactions is 37 degrees.
• Enzymes are very sensitive to the pH of the medium in which a reaction is taking place. Each enzyme has an optimum pH at which it will work most effectively.
• Cofactors are ions or inorganic molecules required by enzymes to catalyze a reaction. Cofactors change the shape of the active site so that the enzyme can combine with the substrate.
• Enzyme inhibitors are substances that slow or even stop the enzymes activity. Inhibitors may be used by cells to control reactions so that products are produced in specific amounts.
• Cellular respiration is the chemical reactions that make energy available for the cell. It is the process by which organic molecules, taken in as food, are broken down in the cells to release energy for the cells activities.
• Equation for cellular respiration:

  C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy (ATP + Heat)

  Glucose + oxygen --> Carbon Dioxide + Water + Energy
• Adenosine + 3 Phosphate groups = ATP
• ATP is formed when an inorganic phosphate group is joined to a molecule of ADP.
• The 2-3 phosphate bond is broken to release energy
• Glycolysis is the first phase in the breakdown of glucose.

  • It doesn't require oxygen
• • Anaerobic respiration is the breakdown of glucose in the absence of oxygen
  • Uses glucose to produce lactic acid and 2 ATP molecules
  • Happens in the cytosol of the cell
  • Supplies the extra energy
• • Aerobic respiration uses oxygen to convert glucose into carbon dioxide and water, producing up to 38 molecules of ATP per glucose molecule.
  • Happens in the mitochondria of the cell.
• Aerobic respiration generates up to 38 molecules of ATP.

  • 2 from glycolysis
  • 2 from the krebs cycle
  • 34 from the electron transport chain
• C6H12O6 + 6O2 --> 6CO2 + 6H20

  38 ADP + 38 P --> 28 ATP
• Glycolysis occurs in the cytoplasm and releases 2 ATP
• The krebs cycle occurs in the mitochondrial matrix and produces 2 ATP