Biological Molecules: Enzymes Flashcards

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1
Q

what are enzymes?

A
  • globular proteins
  • biological catalysts
  • 3D tertiary structure
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2
Q

how do enzymes catalyse a reaction?

A

lowers the activation energy

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3
Q

why are enzymes highly specific?

A

tertiary structure

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4
Q

where do enzymes work?

A
  • at a cellular level to the whole organism
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5
Q

what types of reactions do enzymes catalyse(wide range)?

A
  • intracellular: e.g. photosynthesis and respiration
  • extracellular: e.g. salivary amylase, pepsin
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6
Q

explain the induced fit model of enzyme action.

A
  • substrate binds to the active site, ESC forms
  • as the substrate binds the active site changes shape slightly so that it is complementary to the substrate
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7
Q

what are the properties of enzymes related to?

A
  • its tertiary structure
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8
Q

what are the properties of enzymes?

A
  • they are specific and only catalyse one reaction
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9
Q

why are enzymes specific?

A

only one complementary substrate will bind to the active site

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10
Q

what happens if the substrate shape isn’t complementary to the active site?

A

no ESC is formed, thus the reaction isn’t catalysed

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10
Q

what determines the shape of the active site?

A

the tertiary structure (and this is determined by primary structure)

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11
Q

why do enzymes differ?

A
  • each different enzyme has a different tertiary structure so different shaped active site
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12
Q

what could cause changes to an enzyme and its active site?

A
  • alteration of the tertiary structure (can be caused by a change in pH or temperature)
  • primary structure of a protein is determined by a gene, and if a mutation occurs in that gene, the tertiary structure of the enzyme produced changes
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13
Q

what factors affect the rate of enzyme-controlled reactions?

A
  • enzyme concentration
  • substrate concentration
  • concentration of competitive and non- competitive inhibitors
  • pH
  • temperature
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14
Q

how does enzyme concentration affect the rate of enzyme-controlled reactions?

A
  • increasing enzyme concentration, increases ROR
  • more enzyme molecules in a solution = more likely substrate molecule is to bind with one and form ESC
  • if substrate is limited then adding more enzymes would have no effect at some point
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15
Q

how does substrate concentration affect the rate of enzyme-controlled reactions?

A
  • higher the substrate concentration, faster the reaction = more substrate molecules that are available to bind to the active site
  • this occurs until the saturation point , after that there are too many substrate molecules and all the active sites are occupied
16
Q

how does temperature affect the rate of enzyme-controlled reactions?

A
  • rate of enzyme-controlled reactions increases as temperature increases
  • higher temps = more kinetic energy = faster reactions
  • ESC forms at faster rates
  • at higher temps the enzyme denatures
17
Q

how does pH affect the rate of enzyme-controlled reactions?

A
  • all enzymes have different optimum temperatures
  • above or below the optimum pH, the H+ or OH- ions found in acids and alkalis disrupt the ionic bonds and hydrogen bonds that hold enzymes tertiary structure in place
  • thus the enzyme becomes denatured and the active site changes shape
18
Q

how does competitive inhibitors affect the rate of enzyme-controlled reactions?

A
  • they compete with the substrate molecules as they are similar shapes and bind to the active site
  • this reduces the forming of ESC
19
Q

what is a competitive inhibitor?

A
  • molecules with a similar shape to that of substrate molecules
20
Q

what are non-competitive inhibitors?

A
  • molecules which bind to the enzyme away from its active site
21
Q

how does non-competitive inhibitors affect the rate of enzyme-controlled reactions?

A
  • non-competitive inhibitors bind away from the active site and this causes the shape of the active site to change so substrate molecule no longer binds to it
  • prevent ESC forming
22
Q

what are the models of enzyme action?

A
  • induced-fit model
  • lock and key model
23
Q

what is the lock and key model?

A
  • substrate binds to active site of enzyme as they are complementary to each other
  • ESC forms
  • chemical reaction takes place and products are formed
24
Q

what is the difference between the lock and key model and the induced fit model?

A

the lock and key model suggests that the enzyme is unchanged after the reaction whereas the induced fit model suggests that the enzyme changes shape slightly