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AS Biology > Chapter 3: Enzymes > Flashcards

Chapter 3: Enzymes Flashcards

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1
Q

what are enzymes

A
  • enzymes are globular proteins/fibrous CHONs that catalyse metabolic reactions inside and outside the cell
  • they remain unchanged after catalysis
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2
Q

what are metabolic reactions + types

A
  • biochemical processes

- two types: anabolism and catabolism

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3
Q

what is the active site of the enzyme

A

where the substrate can sit in

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4
Q

what is the function of catalytic residues (part of enzymes)

A

takes part in breaking the bonds of the substrate to catalyse the reaction

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5
Q

what is the function of R groups in enzymes

A
  • holds the substrate in the active site

- forms temporary bonds with substrate

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6
Q

how is the substrate held in the enzyme active site

A

substrate is held by temporary bonds with the r groups of amino acids residues in enzyme active site

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7
Q

what are the two types of enzyme residues

A
  • contact residues

- catalytic residues

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8
Q

what are contact residues

A
  • contact residues fit with the substrate

- these residues determine enzyme specificity

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9
Q

what are catalytic residues

A

catalytic residues act on those bonds in the substrate that are broken by enzyme action

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10
Q

what is a substrate

A

chemical/reactant on which an enzyme works

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11
Q

which enzymes have more specific functions

A
  • sucrase
  • maltase
  • amylase
  • urease
  • catalase
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12
Q

which enzymes have more general functions

A
  • lipase

- protease

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13
Q

what is specificity of enzymes

A
  • 1 type of enzyme only binds to one type of substrate molecule
  • this is because the enzyme active site shape is complementary to the substrate shape
  • only substrates with a complementary shape to the enzyme active site can sit into the enzyme active site
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14
Q

what are the two ways a substrate fits/sits into an enzyme

A
  • lock and key hypothesis

- induced fit hypothesis

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15
Q

what is lock and key hypothesis

A
  • complementary shape fitting
  • both enzymes and substrates were rigid structures that locked into each other very precisely, much like a key going into a lock
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16
Q

what are anabolic reactions

A

Anabolic reactions involve the building of more complex molecules from simpler ones by drawing two or more substrates into the active site, forming bonds between them and releasing a single product

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17
Q

what are catabolic reactions

A

Catabolic reactions involve the breakdown of complex molecules into simpler products, which happens when a single substrate is drawn into the active site and broken apart into two or more distinct molecules

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18
Q

what is induced fit hypothesis

A
  • enzyme would mould around the substrate

- the enzyme function is more general here (e.g. lipase, protease)

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19
Q

what is the quantity of enzymes produced

A
  • enzymes remain unchanged after the reaction
  • enzymes can be reused
  • therefore only a small quantity is produced
  • they have a high turnover rate (means they can catalyse many reactions per unit time)
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20
Q

what is an enzyme substrate complex

A

a temporary complex formed when an enzyme binds to its substrate molecule

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21
Q

what is the product

A

end material of a chemical/enzymatic reaction

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22
Q

what are intracellular enzymes

A
  • act inside cells

- responsible for catalysing reactions that occur in metabolic pathways

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23
Q

what are examples of intracellular enzymes

A
  • anaerobic respiratory enzymes (cytoplasm)
  • aerobic respiratory enzymes (mitochondria)
  • photosynthetic enzymes (chloroplasts)
  • hydrolytic enzymes (lysosome)
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24
Q

what are extracellular enzymes

A
  • an enzyme that is secreted (the release of useful substances out) by a cell
  • functions outside of that cell
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25
Q

what are examples of extracellular enzymes

A
  • amylase secreted into saliva for hydrolysis of starch -> maltose
  • thrombin (protease) secreted into blood plasma for fibrinogen -> fibrin
  • acrosomal enzymes in the sperm acrosome
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26
Q

how do enzymes speed up reactions and increase effective collisions

A
  • reduces activation energy by providing an alternative pathway
  • holds substrates in best position to occur
27
Q

how does the activation energy change upon the addition of an enzyme into a reaction

A

decreases

28
Q

what is the formula for rate of product formation

A

(final product conc. - initial product conc.)/(final time - initial time)

29
Q

what is enzyme activity

A

rate of enzyme catalysed reaction

30
Q

how is enzyme activity measured

A

by measuring the rate of substrate disappearance and the rate of product formation

31
Q

what are the factors affecting enzyme activity

A
  • pH
  • temperature
  • enzyme and substrate concentration
  • inhibitor concentration
32
Q

what is the formula for effect of temperature on reaction rate

A
  • Q10 =2

- everytime the temperature increases by 10C, the rate will double until after optimum temperature

33
Q

how does temperature affect rate when it is significantly below the optimum temperature

A
  • enzyme inactive

- rate of reaction low

34
Q

how does temperature affect rate when the temperature is increasing until optimum temperature

A
  • increase kinetic energy/molecular motion of enzyme and substrate
  • increase frequency of effective collisions
  • more enzyme-substrate complex formed
  • rate increases (Q10=2)
35
Q

how does temperature affect rate when it is optimum temperature

A

maximum capacity

36
Q

how does temperature affect rate above optimum temperature

A
  • kinetic energy continues to increase and atoms in molecules vibrate vigorously until hydrogen bonds are broken and the enzyme is denatured
  • the secondary and tertiary structure is disrupted and the active site shape changes
  • the substrate can no longer fit active site and the enzyme substrate complex is not formed
  • the rate decreases
37
Q

what is the limiting factor of the reaction before the graph plateaus

A

enzyme

38
Q

what is the limiting factor of the reaction after the graph plateaus

A

substrate

39
Q

what is the formula for rate of reaction

A

change in product formation/change in time

40
Q

what does it mean when enzymes are saturated

A

when all active sites on enzymes are occupied

41
Q

what is the limiting factor

A

limits the max rate of reaction

42
Q

what does increasing the limiting factor do

A

increase the rate of reaction

43
Q

what happens to the velocity of the reaction when the substrate concentration increases at low substrate concentration

A

the velocity increases

44
Q

what happens to the velocity of the reaction when it is at high substrate concentration/reaches maximum rate

A

Vmax

45
Q

what is the michealis-menten constant (Km)

A

the michealis-menten constant is the substrate concentration that produces 1/2 Vmax (the substrate concentration when velocity = vmax/2)

46
Q

what does the michealis-menten constant indicate about an enzyme

A

the affinity of an enzyme for its substrate

47
Q

how does Km (michealismenten constant) affect the affinity of an enzyme for its substrate (how does it indicate the affinity)

A
  • the lower the Km, the higher the affinity of binding between the enzyme and its substrate
  • the higher the Km, the lower the affinity of binding between the enzyme and its substrate
48
Q

what are inhibitors

A

inhibitors are small molecules that prevent the normal action of enzymes

49
Q

what are the three concepts of inhibitors

A
  • binding location
  • reversible and irreversible binding
  • competitive or noncompetitive inhibitor
50
Q

what are the inhibitors binding location

A

inhibitors either bind to the active site of the enzyme or the allosteric site

51
Q

how does inhibitors binding location work

A

when the inhibitor sits in the allosteric site, the enzyme changes its structure so the substrate can no longer sit in the active site

52
Q

what are reversible inhibitors

A
  • can bind and leave the enzyme

- usually forms weak bonds with the enzyme

53
Q

what are irreversible inhibitors

A
  • do not leave enzyme after binding
  • usually forms strong bonds with enzyme
  • enzyme is permanently inactivated
54
Q

what are competitive inhibitors

A
  • an inhibitor whereby its ability to inhibit the enzyme depends on substrate concentration
  • the inhibitor occupies the active site and blocks out substrates
55
Q

what are non-competitive inhibitors

A
  • an inhibitor that can inhibit the enzyme regardless of substrate concentration
  • the inhibitor binds to the allosteric site and changes the shape of the enzyme so no substrate can sit in
56
Q

is binding at the active site reversible or irreversible

A

irreversible

57
Q

is binding at the allosteric site reversible or irreversible

A

can be both

58
Q

which inhibitor (competitive or noncompetitive) reaches Vmax/plateaus faster

A

noncompetitve

59
Q

what is a metabolic pathway

A

a series of reactions

60
Q

what is end product inhibition

A
  • when enough product is formed, the metabolic pathway can be switched off by end product inhibition
  • usually its a competitive/non competitive inhibitor
61
Q

what are immobilized enzymes

A

enzymes that have been fixed to a solid surface or trapped inside beads of agar gel

62
Q

how are immobilized enzymes made

A
  • physical absorption e.g. resin
  • physical entrapment e.g. alginate/microcapsule
  • chemical bonding e.g. glutaraldehyde
63
Q

what are the advantages of enzyme immobilisation

A
  • enzyme is easily recovered and reused again
  • the product will not be contaminated by enzymes
  • enhance enzyme stability to temperature and pH changes (held in shape and protected by pH and temperature changes)
  • allow several enzymes to participate in the process simultaneously
64
Q

how are immobilized enzymes used in industry

A
  • lactase - to make lactose free milk
  • amylase - to make high fructose syrup for corn-starch
  • semisynthetic penicillin

AS Biology (11 decks)

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