bio

• Enzymes


  3D (globular) proteins that are biological catalysts
• Active site


  Groove in the protein structure where the substrate fits
• Enzymes


  • They are specific because the shape of active sites of enzymes are different so that only one substrate can fit into the active site
• Lock and key model


  One model of how enzymes work
• In the wrong pH, and at temperatures higher than the optimum


  The active site changes shape so that the substrate will no longer fit into it neatly. The enzyme is said to be denatured.
• Effect of temperature on enzyme activity

  1. At low temperatures the enzyme has low kinetic energy so collides with substrate infrequently

  2. At high temperatures the enzyme is denatured
• Effect of pH on enzyme activity

  On both sides of the optimal pH the enzymes is denaturing because the wrong pH changes the shape of the enzyme
• Effect of substrate concentration on enzyme activity

  1. At low substrate concentration there are more active sites than substrate so increasing the substrate increases rate

  2. At high substrate concentration all active sites are occupied and the enzyme cannot go any faster even if the substrate concentration increases
• Iodine is the test for starch - it goes from yellow to blue-black in the presence of starch
• Rate of enzyme activity

  Change in measurement / change in time
• Synthesis


  Building large molecules from smaller molecules
• Breakdown


  Breaking down large molecules into smaller molecules
• Body temperature is 37oC and normal body pH is 7 except for the stomach which contains hydrochloric acid and so is pH 1-2
• Proteases


  Proteins
• Amylase


  Starch
• Lipase


  Lipid or fat
• Carbohydrases


  Carbohydrates
• Enzymes produced in the body

  • Amylase is produced in saliva, pancreas and small intestine
  • Proteases are produced in the stomach, pancreas and small intestine
  • Lipase is produced by the pancreas and small intestine
• Enzymes are important in digestion for breaking down large food molecules into smaller molecules that can be absorbed from the small intestine into the blood (for distribution around the body)
• Test for starch


  Add yellow iodine and it will turn blue-black if iodine is present
• Test for reducing sugar

  Add Benedicts solution, heat to 80OC and look for a colour change. Brick red - lots of reducing sugar, Orange - moderate amounts of reducing sugar, Green - a little bit of reducing sugar, blue - no reducing sugar.
• Test for protein


  Add a few drops of blue biuret's solution - it will turn purple if protein (amino acids) are present
• Test for lipids


  Add ethanol and shake. Pour the mixture into water and shake again. A white emulsion will form on the surface if fats and oils (lipids) are present
• A calorimeter can be used to determine the amount of energy in food. This involves burning food and transferring the heat energy to water to measure a temperature rise. This gives an indication of the amount of energy.
• The liver produces a substance called bile which is secreted into the small intestine to neutralise stomach acid and help lipids mix with enzyme
• Catalase


  Hydrogen Peroxide
• Starch synthase

  glucose <
• DNA polymerase

  nucleotides
• Polymer


  A chain of repeating units, such as starch is a chain of glucose molecules joined together
• Monomer


  An individual unit of a polymer, eg. glucose is a monomer of starch
• Diffusion


  The net movement of particles from an area of high concentration to an area of low concentration down a concentration gradient
• Diffusion is passive (requires no additional energy)
• Factors affecting rate of diffusion

  1. The higher the temperature, the faster the rate of diffusion

  2. The greater the surface area, the more particles can diffuse from one side to the other

  3. The bigger the concentration difference, the faster the rate of diffusion
• Active transport


  The movement of particles from a low concentration to a high concentration against a concentration gradient
• Active transport requires energy released in respiration
• Cells that carry out a lot of active transport have many mitochondria to provide energy, and transport proteins
• Root hair cells use active transport to absorb mineral ions such as nitrates needed to make proteins
• Osmosis


  The passive movement of water from a dilute solution (high concentration of water) to a more concentrated solution (low concentration of water) through a partially permeable membrane
• Partially permeable membrane


  A membrane that will only let certain particles through it
• Independent variable


  The part of the experiment changed eg. different temperatures