Topic 4

• Role of enzymes


  To catalyse reactions that affect metabolism at a cellular and whole organism level. They affect both structure and function.
• Examples of stuff enzymes help with on the cellular level

  Synthesis of cell components, synthesis of polymers from monomers, release of energy
• Example of thing enzymes help with on the whole organism level

  Digestion
• Specificity of enzymes


  Each enzyme catalyses one of thousands of reactions within a cell.
• Example of intercellular enzyme

  Catalase
• Example of extracellular enzyme


  Amylase, trypsin
• What catalase does


  Ensures that hydrogen peroxide is broken down to form oxygen and water so it doesn't accumulate as hydrogen peroxide is toxic
• Where can you find catalase? (In terms of organisms)

  Plants, animals
• Example of a thing that extracellular enzymes can do


  Break large nutrient molecules into smaller molecules in digestion
• What amylase does


  Breaks starch polymers down into maltose
• What produces amylase?


  Salivary glands, pancreas
• Where is amylase?


  Mouth, pancreatic juice in small intestine
• What trypsin does


  Catalyses the digestion of proteins into smaller peptides which can be broken down into amino acids by other enzymes.
• What produces trypsin?


  Pancreas
• Where is trypsin?


  Pancreatic juice in the small intestine
• General mechanism of enzymes

  An area called the active site within the tertiary structure of an enzyme has a complementary shape to the substrate, the shape is determined by the tertiary structure, substrate binds to active site to form an enzyme-substrate complex, reaction happens, enzyme-product complex forms, products released
• Lock and Key hypothesis

  The shape of the active site is specific to only one substrate so only one substrate will be able to fit into the active site of the enzyme and form an enzyme-substrate complex
• How is the formation of an enzyme-substrate complex good for the efficiency of the process?

  Temporary bonds formed between R-groups in the active site and the substrate will put strain on the bonds within the substrate, making them easier to break.
• How do enzymes speed up a reaction? (Generally)

  They lower the activation energy
• How do enzymes lower activation energy?

  The enzymes help molecules to successfully collide.
• Induced Fit Hypothesis


  The shape of the active site of the enzyme changes shape slightly when a substrate enters as the interactions between the enzyme and substrate will induce changes in the enzyme's tertiary structure, putting strain on the substrate molecule.
• Effect of increasing temperature on rate of enzyme-controlled reaction below optimum temperature

  Enzyme and substrate have more kinetic energy, move around more, increased frequency of effective collisions, increased rate of reaction
• Q10


  A measure of how much the rate increases with a 10 degrees celsius rise in temperature
• Effect of increasing temperature on rate of enzyme-controlled reaction after optimum temperature

  Hydrogen bonds holding the tertiary structure break as the protein vibrates more, breaking bonds changes the tertiary structure and the shape of the enzyme, enzyme has been denatured, shape no longer complementary to the substrate, substrate can't fit in the active site anymore
• Enzyme adaptations of organisms in extremely cold environments

  Flexible structures which make them less stable
• Enzyme adaptations of organisms in extremely hot environments

  More hydrogen and disulfide bonds
• How extreme pHs affect enzymes

  H+ ions can interact with polar and charged R groups, changing the concentration of H+ ions changes the degree of interaction, a higher concentration of H+ means the R groups will be able to interact with each other less, this breaks bonds and thus changes the shape of the enzyme,
• Renaturation


  The returning of an enzyme to its original shape
• How substrate and enzyme concentrations affect rates of enzyme-controlled reactions

  If concentration is increased, the number of substrate or enzyme molecules in a particular volume increases so there is a higher collision rate with the active site of enzymes and more enzyme-substrate complexes form
• Does Q10 apply after denaturation?

  No
• How to investigate the effect of conditions on enzymes

  Add catalase in liver tissue to hydrogen peroxide in a conical flask with a delivery tube leading to a boiling tube partially submerged underwater, measure the volume of oxygen every five seconds, change the conditions for this reaction and plot graphs
• How to investigate the effect of temperature on enzymes

  Boil the liver before adding it to hydrogen peroxide
• Controlled variables in investigating the effect of conditions on enzymes

  Concentration of hydrogen peroxide, volume of hydrogen peroxide, mass of liver tissue, surface area of liver tissue
• Why are controlled variables important?

  So only the independent variable changes
• How to investigate the effect of concentration on catalase

  Grind up potato or liver to make a solution, serial dilution of the solution to make different relative concentrations, add equal volumes of a concentration of hydrogen peroxide to each solution
• Coenzyme


  Organic cofactor
• How we get inorganic cofactors

  Minerals in diet
• How we get coenzymes

  Vitamins in diet
• Things cofactors can do

  Transferring atoms from one reaction to another in a multi-step pathway, forming part of the active site
• Prosthetic groups


  A type of cofactor