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0. Foundations of Medicine > Enzymes 1 > Flashcards

Enzymes 1 Flashcards

1
Q

<p>What are virtually all reactions in the body mediated by?</p>

A

<p>Enzymes</p>

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2
Q

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

A

<p>A biological catalyst that increases the rate of a reaction without being changed in the overall process</p>

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3
Q

<p>How are enzymes efficient?</p>

A

<p>They catalyse at a very high reaction rate</p>

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4
Q

<p>What is meant by the specificity of enzymes?</p>

A

<p>They are very specific, with only certain substrates binding to them</p>

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5
Q

<p>Are can enzyme reactions be controlled?</p>

A

<p>They can be regulated</p>

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6
Q

<p>What pH and temperature conditions do enzymes work in?</p>

A

<p>Mild</p>

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7
Q

<p>How do the set of enzymes in a cell determine which metabolic pathways take place?</p>

A

<p>They are so specific</p>

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8
Q

<p>What are ribozymes?</p>

A

<p>Catalytic RNA molecules with no protein content</p>

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9
Q

<p>What are enzymes named and classified according to?</p>

A

<p>The reactions that they catalyse</p>

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10
Q

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

A

<p>Non protein component needed for activity</p>

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11
Q

<p>What is usually the cofactor?</p>

A

<p>An ion such as Fe2+, Fe3+, K+or Mg2+</p>

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12
Q

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

A

<p>Complex organic molecule that is usually produced from vitamins</p>

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13
Q

<p>Give some examples of coenzymes?</p>

A

<p>FAD (comes from riboflavin)</p>

<p>NAD (comes from niacin)</p>

<p>Coenzyme A (comes from pantothenate)</p>

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14
Q

<p>What is a prosthetic group?</p>

A

<p>Cofactor covalently bound to an enzyme or very tight associated with the enzyme</p>

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15
Q

<p>What is an example of a prosthetic group?</p>

A

<p>The haem in haemoglobin</p>

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16
Q

<p>What is an apoenzyme?`</p>

A

<p>Protein component of an enzyme that contains a cofactor</p>

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17
Q

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

A

<p>'Whole enzyme', the apoenzyme plus the cofactor</p>

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18
Q

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

A

<p>Molecules acted on by an enzyme</p>

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19
Q

<p>What is the active site?</p>

A

<p>Part of an enzyme in which the substrate bind and is acted upon</p>

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20
Q

<p>What does the name of an enzyme normally end in?</p>

A

<p>-ase, the name also normally relates to the function</p>

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21
Q

<p>What are the 6 classes of enzymes?</p>

A

<p>Oxidoreductases</p>

<p>Transferases</p>

<p>Hydrolases</p>

<p>Lyases</p>

<p>Isomerases</p>

<p>Ligases</p>

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22
Q

<p>What do oxidoreductases do?</p>

A

<p>Transfer electrons</p>

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23
Q

<p>What do transferases do?</p>

A

<p>Transfer groups</p>

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24
Q

<p>What do hydrolases do?</p>

A

<p>Hydrolyse (transfer chemical groups to water)</p>

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25
Q

<p>What do lyases do?</p>

A

<p>Form or add groups to double bonds</p>

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26
Q

<p>What do isomerases do?</p>

A

<p>Transfer groups within molecules (form isomers)</p>

27
Q

<p>What do ligases do?</p>

A

<p>Formation of C-C, C-S, C-O and C-N (coupled to ATP cleavage)</p>

28
Q

<p>What are two things that enzymes do not do to a reaction?</p>

A

<p>Move the reaction equilbrium</p>

<p>Make a non spontaneous reaction spontaneous</p>

29
Q

<p>What are 3 things that enzymes do?</p>

A

<p>Increase the rate of a spontaneous reaction</p>

<p>Lower the activation energy of biochemical reactions</p>

<p>Accerlerate movement towards equilbrium</p>

30
Q

<p>What delta G value must spontaneous reactions have?</p>

A

<p>Negative so they will increase entropy</p>

31
Q

<p>When does the transition state occur?</p>

A

<p>When the stable molecules become unstable and may carry on to the product or revert back to the substrate</p>

32
Q

<p>Why are spontaneous reacitons not instantaneous?</p>

A

<p>Because of the energy barrier</p>

33
Q

<p>What is the energy barrier?</p>

A

<p>Energy required to position chemical groups correctly, bond rearrangments, e-rearrangement etc</p>

34
Q

<p>What does an enzyme allow a reaction to occur through?</p>

A

<p>A different route</p>

<p>E+S⇔ ES⇔ EP⇔ E + P</p>

35
Q

<p>What does induced fit mean?</p>

A

<p>Conformation changes in protein structure when the substrate binds</p>

36
Q

<p>What are 3 techniques used to analyse an enzymes?</p>

A

<p>Mutagenesis</p>

<p>3D structure</p>

<p>Enzyme kinetics</p>

37
Q

<p>What would happen to the initial rate of a reaction if we changed the substrate concentration?</p>

A

<p>The initial rate of the ration would also change</p>

38
Q

<p>Why does the rate of the reaction decrease as time proceeds?</p>

A

<p>The substrate is used up</p>

39
Q

<p>How can the initial velocity (vo) be studied?</p>

A

<p>By knowing the precise [S], and having lots of S</p>

40
Q

<p>What happens to voas initial [S] increases?</p>

A

<p>It increases until it levels out due to all of the enzymes active sites being used</p>

41
Q

What does a graph of substrate concentration against vo look like?

42
Q

<p>Why at higher [S] does vochange very little?</p>

A

<p>Due to the finite number of enzymes</p>

43
Q

<p>What is vmax?</p>

A

<p>Occurs when [S] becomes so large that vochanges a vanishably small amount (all enzyme active sites are saturated with substrate)</p>

44
Q

<p>When does vmaxoccur?</p>

A

<p>When all enzyme sites are saturated with substrate</p>

45
Q

<p>What is the model that Machaelis and Menten proposed to acount for the curve of [S] against vo?</p>

A

<ol> <li>First part of the reaction occurs reversible</li> <li>Second part occurs more slowly</li></ol>

46
Q

<p>What limits the rate of the entire reaction?</p>

A

<p>The second step (ES to E + P) is the slowest step and so is the rate determining step</p>

47
Q

<p>What is the rate of the reaction proportional to?</p>

A

<p>Amount of ES</p>

48
Q

<p>What is KM(Michaelis constant)?</p>

A

<p>Substrate concentration at half of the vmax</p>

49
Q

What is the M-M equation?

A

rate equation for a one-substrate enzyme-catalyzed reaction

50
Q

<p>Whats happens to the M-M equation when [S] is equal to KM?</p>

A

<p>It looks like Vo= Vmax/2</p>

51
Q

<p>What is the steady state assumption?</p>

A

<p>[ES] does not change with time due to the rate of formation being equal to the rate of breakdown</p>

52
Q

<p>Why is it hard to determin vmaxusing the graph of [S] against vo?</p>

A

<p>The graph curves and basically goes to infiity</p>

53
Q

<p>What is the most accurate way to determine vmaxexperimentally?</p>

A

<p>Drawing a Lineumer-Burk plot (double reciprical plot)</p>

54
Q

<p>That does the intersection of the y-axis on a Lineurner-Burk plot represent?</p>

A

<p>1/vmax</p>

55
Q

<p>What does the intersection of the x-axis on a Lineumer-Burke plot represent?</p>

A

<p>1/KM</p>

56
Q

<p>What can KMalso be defined as?</p>

A

<p>KM= (K-1+ K2) / K1</p>

<p>Because K2is the rate limiting step (K2< K-1):</p>

<p>KM= K-1/ K1</p>

57
Q

<p>What can KMalso be termed as?</p>

A

<p>The dissociation constant of the ES complex</p>

58
Q

<p>What can KMbe described as it terms of rate?</p>

A

<p>Ratio of rate constant for break of ES to E+S compared to the ratio contant for formation of ES from E+S</p>

59
Q

<p>What does KMindicate about an enzyme and a substrate?</p>

A

<p>The affinity of the enzyme with that substrate</p>

60
Q

<p>What does a large KMmean?</p>

A

<p>Less stable ES complex (low affinity)</p>

61
Q

<p>What does a low KMmean?</p>

A

<p>More stable ES complex (high affinity)</p>

62
Q

<p>What does vmaxtell you?</p>

A

<p>How fast the reaction is proceeding when the enzyme is saturated with substrate</p>

63
Q

<p>What do KMand vmaxchange in response to?</p>

A

<p>The cells condition, the same enzyme may function differently in different cells</p>

0. Foundations of Medicine (167 decks)

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