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0. Foundations of Medicine > Enzymes 2 > Flashcards

Enzymes 2 Flashcards

1
Q

<p>Give an example of two enzymes that catalyse the same reaction?</p>

A

<p>Glucokinase and hexokinase</p>

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2
Q

<p>What reaction to glucokinase and hexokinase catalyse?</p>

A

<p>Glucose + ATP→ Glucose-6-phosphate + ADP</p>

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3
Q

<p>Where is glucokinase found?</p>

A

<p>In the liver</p>

<p></p>

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4
Q

<p>Where is hexokinase found?</p>

A

<p>Everywhere other than the liver</p>

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5
Q

What kinetic properties do glucokinase and hexokinase have (KM and vmax)

A
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6
Q

<p>What does a graph of the activity of glucokinase and hexokinase look like and explain it?</p>

A

<p>Hexokinase is constantly working flat out whereas glucokinase can respond proportionally to blood glucose</p>

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7
Q

<p>Why does hexokinase have a low KM?</p>

A

<p>So it can respond proportionally to blood glucose</p>

<p>When [glucose] is low you don't want the liver to break it down as you want it to be released into the blood</p>

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8
Q

<p>What is the difference between glucose-6-phosphate and glucose?</p>

A

<p>G-6-P cannot leave the cell</p>

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9
Q

<p>What do enzymes being found where they shouldn't be indicate?</p>

A

<p>Tissue damage, enzymes may escape from damaged cells</p>

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10
Q

<p>How is enzyme activity measured in clinical scenarioes?</p>

A

<p>With an arbitory value</p>

<p>1U/ml o 100% = normal</p>

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11
Q

<p>What is an isozyme?</p>

A

<p>Different enzymes that catalyse the same reaction</p>

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12
Q

<p>Where are isoenzymes often found relative to each other?</p>

A

<p>In different tissues</p>

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13
Q

<p>Are isoenzymes coded for by the same gene?</p>

A

<p>No, they are products of different genes</p>

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14
Q

<p>What is electrophoresis?</p>

A

<p>Process where you can seperate out biological molecules</p>

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15
Q

<p>How does electrophoresis work?</p>

A

<p>Larger molecules get stuck and so move less than smaller molecules, charge also has an impact</p>

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16
Q

<p>What is creatine kinase (CK)?</p>

A

<p>An example of an isoenzyme which is a dimer made up from two polypeptide chains B and M</p>

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17
Q

<p>What is a dimer?</p>

A

<p>Oligomer consisting of two monomers joined by bonds that can be strong or weak, covalent or intermolecular</p>

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18
Q

<p>What is an oligomer?</p>

A

<p>Molecule complex of chemicals that consists of a few monomer units</p>

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19
Q

<p>What are the 3 isomorms that creatine kinase (CK) can form?</p>

A

<p>CK1 (BB)</p>

<p>CK2 (BM)</p>

<p>CK3 (MM)</p>

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20
Q

<p>How are enzymes used in diagnosis?</p>

A

<p>Measure activity and compare with normal</p>

<p>Sepperate differnt forms of enzymes by electrophoresis</p>

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21
Q

<p>Are enzymes restricted to interacting with one substance?</p>

A

<p>No, most enzymes can interact with a variety of substances</p>

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22
Q

<p>How does the KMvary between enzymes and their different substrates?</p>

A

<p>Changes for each substrate</p>

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23
Q

<p>What does catalysing a reaction with two or more substances normally involve?</p>

A

<p>The transfer of groups from one to the other</p>

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24
Q

<p>What ways can the catalyse of two or more substances with the transfer of groups occur?</p>

A

<p>Random order or ordered with ternary complex</p>

<p>No ternary complex formation</p>

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25
Q

What does a random order reaction involving a ternary complex look like?

A
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26
Q

What does an ordered reaction involving a ternary complex look like?

A
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27
Q

With does a reaction with no formation of a ternary complex look like?

A
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28
Q

<p>What is an example of an enzyme that uses an ordered sequential mechanism?</p>

A

<p>Lactate dehydrogenase for the reaction of pyruvate to lactate</p>

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29
Q

<p>What is an example of an enzyme that uses a random sequential mechanism?</p>

A

<p>Creatine kinase (CK) for creatine to phosphocreatine</p>

30
Q

<p>What do ordered and unordered squential mechanisms have in common?</p>

A

<p>The ternary complex is formed first</p>

31
Q

<p>What is an example of an enzyme that uses a no formation of tertary complex mechanism?</p>

A

<p>Asparate aminotransferase, uses a double displacement reaction</p>

32
Q

<p>What is a double displacement reaction?</p>

A

<p>Substrates bounce on and off the enzyme</p>

33
Q

<p>What happens when you take an amino group of an amino acid?</p>

A

<p>It becomes a ketoacid</p>

34
Q

<p>What notation is commonly used to show the mechanisms of enzyme reactions?</p>

A

<p>Clelend notation</p>

35
Q

<p>What is an allosteric enzyme?</p>

A

<p>Enzymes made up of many subunits</p>

36
Q

<p>What sites are on an allosteric enzyme?</p>

A

<p>Can contain many active sites, they have other sites that can be used for regulation</p>

37
Q

<p>What do the kinetics of an allosteric enzyme look like and why is this?</p>

A

<p>Because of cooperative binding</p>

38
Q

<p>What is cooperative binding?</p>

A

<p>One substance binds to an enzyme subunit causing a change in the acitve site of other sub units</p>

39
Q

<p>What is an example of an enzyme that uses cooperative binding?</p>

A

<p>Haemoglobin</p>

40
Q

<p>What factors affect the way that enzymes function?</p>

A

<p>Temperature</p>

<p>pH</p>

<p>Inhibition</p>

41
Q

<p>How does temperature affect enzyme functionality?</p>

A

<p>As temperature increases, molecule collisions increase</p>

<p>As temperature increases, internal energy of molecule increases</p>

<p>If temperature increases further the enzyme will denature</p>

42
Q

<p>How does pH affect enzyme functionality?</p>

A

<p>Changes charge of amino acids</p>

<p>If the active amino acids change charge will stop working</p>

<p>Extreme pH will denature the enzyme</p>

<p>Also affects substrates</p>

43
Q

<p>What are the three types of inhibitors?</p>

A

<p>Competative inhibitor</p>

<p>Non-competative inhibitor</p>

<p>Uncompetative inhibitor</p>

44
Q

<p>What is a competative inhibitor?</p>

A

<p>Binds to the active site non covalently, competing with the substrate</p>

45
Q

<p>What do competative enzymes cause in terms of enzyme kinetics?</p>

A

<p>Decreased affinity (KMincrease)</p>

<p>vmaxremains the same as increasing [substrate] can overcome it</p>

46
Q

<p>What does the best inhibitor look like and why?</p>

A

<p>The transition state because it binds better</p>

47
Q

<p>Why are there not a lot of transition state drugs?</p>

A

<p>The transition state is hard to determine</p>

48
Q

<p>What are non-competative inhibitors?</p>

A

<p>Bind to somewhere other than the active site non covalently</p>

49
Q

<p>What do non-competative inhibitors cause in terms of enzyme kinetics?</p>

A

<p>KMunchanged as substrate can still bind</p>

<p>vmaxdecreases because cannot out compete the inhibitor</p>

50
Q

What do inhibitors on a Lineweaver-Burk plot look like?

A
51
Q

<p>What is an example of an irreversible inhibitor?</p>

A

<p>Cyanide (CN-)</p>

52
Q

<p>What does biological reactions occuring in pathways allow?</p>

A

<p>Regulation of a key step byt regulating the enzyme, often the first step</p>

53
Q

<p>What are the 2 main ways of regulating enzymes?</p>

A

<p>Allosteric enzymes</p>

<p>Covalently modified enzymes</p>

54
Q

<p>What is feedback inhibition?</p>

A

<p>Build up of an end product inhibits an earlier enzyme</p>

55
Q

<p>What kind of inhibition do pathways often use?</p>

A

<p>Feedback inhibition</p>

56
Q

<p>What are allosteric effectors?</p>

A

<p>Cell metabolites that bind non covalently to a site on the enzyme that is not the active site</p>

57
Q

<p>What do effectors do to an enzyme structure?</p>

A

<p>Cause it to change</p>

58
Q

<p>What are the two types of effectors?</p>

A

<p>Inhibitor</p>

<p>Activator</p>

59
Q

<p>What two models explain allosteric kinetics?</p>

A

<p>Concerted model</p>

<p>Sequential model</p>

60
Q

<p>What does the concerted model state?</p>

A

<p>Sub units exist in two conformations (one binds well and the other doesn't)</p>

<p>With no substance the enzyme flips between the two conformations</p>

<p>All sub units must be in the same conformation (flip in concert)</p>

61
Q

<p>What are allosteric activators?</p>

A

<p>Bind somewhere other than the active site, locking the open conformation</p>

62
Q

<p>What are allosteric inhibitors?</p>

A

<p>Bind somewhere other than the active site, locking in the closed conformation</p>

63
Q

<p>What are the properties of the sequential model?</p>

A

<p>Substrate binding causes a change in one subunit</p>

<p>Binding causes conformational change</p>

64
Q

<p>What is an example of a reversible covalent modificaiton that can inhibit an enzyme?</p>

A

<p>Being phosphorylated</p>

65
Q

<p>What are the two kinds of enzymes that catalyse the phosphorylation of an enzyme?</p>

A

<p>Protein kinases (adds phosphory group to a protein)</p>

<p>Protein phophotases (removes phosphoryl group)</p>

66
Q

<p>What do multiple phosphorylation sites allow?</p>

A

<p>Fine control of an enzymes function, it is never completely off or on but is finely tuned</p>

67
Q

<p>What is a proprotein?</p>

A

<p>Enzymes existing as an inactive precurser protein</p>

68
Q

<p>What happens when the proprotein is cleaved of an enzyme?</p>

A

<p>Enzyme becomes active by proteases</p>

69
Q

<p>What kinds of enzymes often use proprotein for regulation?</p>

A

<p>Digestive enzymes</p>

70
Q

<p>What is proteolysis?</p>

A

<p>Process of breaking peptide bonds between amino acids</p>

71
Q

<p>What is a protease?</p>

A

<p>Enzymes that perform proeolysis (protein catabolism by hydrolysis of peptide bonds)</p>

0. Foundations of Medicine (167 decks)

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