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BDS1 BAMS molecules and cells > enzymes > Flashcards

enzymes Flashcards

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Organic Chemistry 101 flashcards
1
Q

what are enzymes?

A

biological catalysts in living cells which speed up chemical reactions whilst remaining unchanged- essential for survival

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2
Q

what do enzymes do to the equilibrium?

A
  • DO NOT alter the equilibrium
  • just accelerate the time taken to reach the equilibrium
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3
Q

what is enzyme alkaline phosphatase involved in?

A

mineralisation of tissue and bone

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4
Q

what is enzyme amylase involved in?

A

found in saliva, converts starch into sugars

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5
Q

what is enzyme maltase involved in?

A

found in saliva, breaks sugar maltose into glucose

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6
Q

what is enzyme lysozyme involved in?

A

antimicrobial, breaks down the peptidoglycan layer in the cell wall of bacteria

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7
Q

what is enzyme pepsin involved in?

A

digestion in stomach, breaks down proteins into smaller peptides

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8
Q

what is enzyme trypsin involved in?

A

found in small intestine, breaks down proteins into amino acids

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9
Q

what is enzyme acetylcholinesterase involved in?

A

breaks down the neurotransmitter acetylcholine in nerves and muscles

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10
Q

what is enzyme DNA polymerase involved in?

A

synthesises DNA from doexyribonucleotides

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11
Q

what are the two ways in which an enzyme can work?

A
  • lock and key
  • induced fit
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12
Q

what is lock and key?

A

Enzyme active site complementary in shape to that of substrate
Active site precisely shaped to hold specific substrates

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13
Q

what is induced fit?

A

Active site and substrate do not fit together exactly
Enzyme changes shape when substrate binds
Active site has a shape complementary to the substrate only after the substrate has bound

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14
Q

what is induced fit?

A

Active site and substrate do not fit together exactly
Enzyme changes shape when substrate binds
Active site has a shape complementary to the substrate only after the substrate has bound

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15
Q

what kind of molecule are most enzymes?

A

proteins (exceptions are catalytic RNA molecules)

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16
Q

what affects the nature of an enzyme?

A

pH
temperature

17
Q

what is the optimum?

A

the conditions at which the enzyme works best at

18
Q

what happens to the enzyme at extreme conditions?

A

it may lose its 3D structure- denature, and become totally inactive

19
Q

what is the standard free energy change of a reaction? (G)

A

Difference between energies of reactants (initial state) and products (final state) is the

20
Q

what is the activation energy of a reaction? (Ea)

A

the energy input required to initiate a reaction

21
Q

what effect do enzymes have on activation energy?

A

enzymes lower activation energy (enzymes cannot alter free energy)

22
Q

what are factors which can affect the rate of an enzyme reaction?

A

Temperature
pH
Enzyme concentration
Substrate concentration
Inhibitors and activators
Covalent modification

23
Q

what will an increase in enzyme concentration do to a reaction?

A

increase the reaction rate

24
Q

what effect does increasing substate concentration have on the rate of an enzyme reaction?

A

originally, increasing S will increase reaction rate, until all active sites are occupied whereafter it will remain constant

25
Q

what is Vmax?

A

the maximum rate of reaction, where the enzyme is saturated with substrate

26
Q

what does the relationship between reaction rate and substrate concentration depend on?

A

affinity (Km) of an enzyme for its substrate

(Km is the concentration of substrate at which the rate of reaction is half its max value)

27
Q

what is the difference between a low Km and high Km?

A

Low Km: enzyme is normally saturated with substrate, acts at a fairly constant rate regardless of variations in substrate concentration

High Km: enzyme is not normally saturated with substrate, its activity will vary as substrate concentration varies – rate of product formation depends on substrate availability

28
Q

what happens to substrate concentration overtime?

A

decreases

29
Q

what are the two types of enzyme inhibitors?

A
  • irreversible
  • reversible
30
Q

describe irreversible inhibitors

A
  • damage enzymes beyond repair
  • generally cause covalent modification of the enzyme
31
Q

describe reversible inhibitors

A
  • full enzyme activity is regained when the inhibitor is removed
  • most natural enzyme inhibitors fall into this category
32
Q

what is feedback inhibition?

A
  • When the product of a metabolic pathway builds up in the cell, inhibition of the pathway often occurs
  • This is often done by the product of the pathway acting as an inhibitor of an earlier step in the pathway
  • This is known as feedback inhibition
  • An example of this is the pathway that forms isoleucine from threonine
33
Q

what types of inhibitors are there?

A
  • competitive
  • non-competitive
34
Q

what is a competitive inhibitor?

A

Substrate and inhibitor compete for same active binding site – structural analogues, prevent substrate from binding
Inhibition can be overcome (reversible) with large quantities of substrate – substrate will ultimately occupy all binding sites, enzyme fully operative

35
Q

what is non-competitive inhibition?

A

Bind to an allosteric site on the enzyme i.e. one other than active site
Structurally unrelated to substrate
Inhibition cannot be reversed by adding large quantities of substrate

36
Q

what is an allosteric enzyme?

A
  • Allosteric enzymes possess multiple subunits
  • In addition to active sites they also possess regulatory (allosteric) sites to which non-substrate modulators bind, creating conformational change in subunits
  • Subunits interact such that the binding of a substrate, inhibitor, or activator to one subunit alters the conformation of all the subunits:
    • positive modulators (increase affinity for substrate at active site)
    • negative modulators (decrease affinity for substrate at active site)
  • Many important regulatory enzymes are allosteric
37
Q

what is a common enzyme modification?

A

addition of a phosphate group to serine, threonine, tyrosine or hydroxyl group

BDS1 BAMS molecules and cells (20 decks)

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