Chapter 4- Enzymes

• state two examples of competitive inhibitors

  STATINS

  • competitive inhibitors of an enzyme which synthesises cholesterol, prevents synthesis of cholesterol 
  • Helps people reduce blood cholesterol 

  APSPIRIN

  • Irreversibly inhibits the active site of COX enzymes
  • Preventing synthesis of prostaglandins and thromboxane, responsible for producing pain and fever 
• State two examples of non competitive inhibition

  ORGANOPHOSPHATES

  • Insecticides and herbicides
  • Irreversibly inhibit enzyme acetyl cholinesterase, necessary for nerve impulse transmission
  • Can lead to cramps, paralysis or even death

  PROTON PUMP INHIBITORS

  • Used to treat long term indigestion
  • Irreversibly block enzyme system responsible for secreting H ions into the stomach
  • Prevents stomach ulcers
• What is inorganic between a cofactor and coenzyme?

  Cofactor=inorganic

  • C
  • O
  • Factor
  • Is
  • Not organic
• How are inorganic cofactors obtained

  In the diet as mineral ions/minerals
• What cofactor does amylase contain? What does it do and why is it a coenzyme, not a cofactor?

  • Contains a chloride ion
  • Necessary for the formation of correctly shaped active site
  • Is inorganic, and a mineral/ion
• What are many coenzymes derived from?

  Vitamins
• What are prosthetic groups?

  • Cofactors
  • Required by enzymes to carry out specific functions
  • Permanent feature of the protein (unlike some cofactors which are temporarily bound)
• State two examples of a prosthetic group

  • Zinc ions form part of the structure carbonic anhydrase
  • Carbonic anhydrase is necessary for the metabolism of carbon dioxide
  • Each haem group in Haemoglobin contains iron (Fe2+) which binds reversibly to carbon dioxide oxygen and water, and irreversibly to carbon monoxide
• What are precursor enzymes?

  enzymes produced in an inactive form
• Why are enzymes produced in an inactive form as precursor enzymes?

  • May cause damage within the cell producing them or tissues where they are released
  • Enzyme action may need to be controlled and only activated under certain conditions
• What needs to happen to a precursor enzyme for it to be activated?

  • Change in tertiary structure to the active site
  • Can be achieved by the addition of a cofactor
• What is a precursor enzyme called before and after a cofactor is added?

  • Before- apoenzyme
  • After- holoenzyme
• What is an enzyme that can be activated by a change in conditions eg- pH or temperature?

  zymogens or proenzymes
• State an example of an intercellular enzyme

  • Hydrogen peroxide
  • Catalase breaks it down into oxygen and water
  • found in both animal and plant tissues
• Why do nutrients need to be broken down outside cells sometimes?

  • Some in the form of polymers are too large to enter through the cell surface membrane
  • So need to be broken down into smaller components
• State examples of single celled organisms that have extracelluar enzymes

  • Fungi
  • Bacteria
  • Yeast
• State examples of extracellular enzymes inside humans

  • Amylase- digests starch
  • Trypsin- digests proteins
• Explain how pH affects enzyme activity

  • Hydrogen bonds between AA R groups hold enzymes in their precise 3D shape
  • Increase in pH means more hydrogen ions will interact with R groups, which prevent R groups from interacting with each other
  • More hydrogen ions present, the less the R groups can interact with each other and bonds break
  • therefore the shape of the active site changes and enzymes are no longer complementary to the substrate