Catalysis

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Anonymous
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194197
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Catalysis
Updated:
2013-01-21 12:09:43
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Biology
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Description:
Advanced Higher Biology - Unit One - Catalysis
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  1. Most catalysis in cells is done by...?
    enzymes
  2. Are enzymes fibrous or globular proteins?
    Globular
  3. What is the difference between monomeric and oligomeric enzymes?
    Monomeric enzymes have only one polypeptide chain whereas oligomeric enzymes have several polypeptide chains
  4. What does a synthase enzyme do?
    Joins two molecules together by a dehydration (condensation) reaction
  5. What does a kinase enzyme do?
    Transfers a phosphate group to another molecule eg carbohydrate or protein
  6. What does a polymerase enzyme do?
    It adds nucleotide monomers in sequence (by condensation) to a polymer eg DNA or RNA (by a phosphodiester bond)
  7. What does a ligase enzyme do?
    It joins two strands of nucleic acid polymer (by condensation creating a phosphodiester bond)
  8. What does a hydrolase enzyme do?
    Catalyse a hydrolysis reaction
  9. What does a protease enzyme do?
    Hydrolyses a peptide bond to break down protein into animo acids eg pepsin and trypsin
  10. What does a nuclease enzyme do?
    Hydrolyses phosphodiester bonds to break down nucleic acids into nucleotides eg restriction enzymes such as Eco R1
  11. What does a ATPase enzyme do?
    Hydrolyses phosphodiester bonds in ATP to form ADP + Pi eg sodium-potassium pump
  12. What does a phosphatase enzyme do?
    Removes a phosphate from a molecule by hydrolysis
  13. Enzymes work by lowering...?
    activation energy
  14. How do catalysts lower the energy needed to start a chemical reaction?
    By binding to two substrates to force them close together or by stressing the chemical bonds in the molecule to break them down
  15. When the correct substrate molecule binds to the enzyme there is a __________ change in the shape of the active site of the enzyme to fit the substrate better?
    conformational
  16. What term is used to describe when the presence of a substrate causes the active site of the enzyme to change shape?
    Induced fit
  17. What dictates the shape and the bonds/attraction forming between the enzyme active site and substrate?
    The amino acid sequence of the enzyme
  18. What is competitive inhibition?
    When an inhibitor binds to the enzymes active site preventing substrate binding
  19. What is non-competitive inhibition?
    When an inhibitor binds to a second (differenct) site on the enzyme resulting in a conformational change of the enzyme and preventing substrate binding
  20. What are allosteric enzymes?
    Enzymes that have two conformations - one which is active and one which is not
  21. Allosteric enzymes undergo a conformational (shape) change in response to binding of a _______ molecule (modulator/effector)?
    regulating
  22. What is the difference between activators and inhibitors?
    Activators have a positive effect by stabilising the enzymes active form whereas inhibitors have a negative effect by stablilising the enzymes inactive form
  23. What is covalent modification of an enzyme?
    The addition or removal of chemical groups on the enzyme
  24. Explain end product inhibition
    This is a form of negative feedback.  The end product of a biochemical pathway binds to the first enzyme (in the pathway) inhibiting it.  This prevents intermediates being made and reduce the amount of end product being made
  25. What type of molecules are extracellular hydrophobic signalling molecules?
    Steriod hormones eg testosterone
  26. How do extracellular hydrophobic signalling molecules work?
    These can diffuse across the plasma membrane of the target cell and activate gene regulatory proteins which regulate the transcription of specific genes
  27. What type of molecules are extracellular hydrophillic signalling molecules?
    • Peptide hormones eg insulin
    • Neurotransmitters eg noradrenalin and acetylcholine
  28. How do extracellular hydrophillic signalling molecules work?
    These activate receptor proteins on the surface of the targer cell.  The receptors acts as transducers, converting the extracellular binding event into intracellular signals which alter the behaviour of the target cell

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