CHAPTER 3: ENZYMES Flashcards

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1
Q

what are biochemical pathways

A
  • biochemical reactions: chemical reactions that occur in living things
  • a biochemical pathway is a series of interconnected biochemical reactions
    • eg. cellular respiration and photosynthesis
    • each step requires a specific enzyme
    • the product formed by one step of the pathway becomes the reactant for the next step of the pathway and so on
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2
Q

why are enzymes needed in living things

A
  • catalyze reactions like growth, repair, cellular respiration, photosynthesis, reproduction, digestion, breathing
  • enzymes increasing the rate of chemical reactions (which would otherwise occur too slowly to sustain life)
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3
Q

what are enzymes

A
  • are proteins made of 1 or more polypeptides
  • speed up chemical reactions - are catalysts
  • substrate specific
  • have an active site
  • works best in certain conditions
  • are not used up in the reaction
  • the shape (3d structure) is crucial
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4
Q

types of reactions

A
  • catabolic reactions: occurs when a large substrate is broken down into smaller products
    • energy is released → cellular respiration
  • anabolic reactions: occurs when smaller substrates are joined to form a larger product
    • energy is used → photosynthesis
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5
Q

how do enzymes speed up chemical reactions

A
  • enzymes allow chemical reactions to occur at a greater rate by lowering the activation energy of the reactions
  • enzymes bring molecules close together in the correct orientation and bend the substrate to allow bonds to break or form easily
  • as activation energy is lower when the enzyme is used, more substrate molecules and enzymes will have sufficient energy to react when they collide
  • They DO NOT change the direction of the reaction nor do thy change the amount of product produced
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6
Q

what is activation energy

A

the minimum amount of energy required to initiate a chemical reaction

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7
Q

induced fit model vs lock and key model
draw a diagram too

A
  • induced fit model:
    • the shape of the active site is not rigid and can adjust to the shape of its substrate
  • lock and key model
    • substrate and enzyme fit together rigidly and tightly
      the substrate exactly fits into the enzyme
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8
Q

what is a coenzyme

A
  • they are organic, non-protein molecules that bind loosely with an enzyme at its active site, assisting the catalytic function of the enzyme
  • bound to their enzyme only when the enzyme is acting on a substrate to alter the rate of reaction
  • they act with an enzyme to alter the rate of a reaction and can:
    • bind to the active site to help the substrate fit
    • cycle energy protons, hydrogen, and electrons around the cell
    • act as shuttles → transfers atoms and energy
  • exists in two inter-convertible forms
    • high energy form that is loaded w/ a group that can be transferred
    • a lower energy form that is unloaded
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9
Q

role of ATP

A
  • energy-rich and its major role is to transfer energy within cells
  • this energy is made available when the last phosphate group of ATP is removed to form ADP
  • transfers both energy and donates a phosphate group to substrates
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10
Q

role of NADP+

A

acts as hydrogen donors and in the transfer of energy in photosynthesis

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11
Q

role of FAD

A
  • the unloaded form acts as a hydrogen and electron acceptor (FAD)
  • the loaded form acts as a hydrogen and electron donor (FADH2)
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12
Q

role of NAD+

A
  • unloaded NAD+ is a receiver/acceptor of electrons and hydrogen ions from substrates
  • loaded NADH transfer their hydrogens and electrons in the last stages of cellular respiration
    • catalyses reactions in which substrate is reduced and needs to gain hydrogen ions and electrons
    • when NADH unloads its electrons the energy released is transferred via a number of steps and is used to produce ATP
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13
Q

factors affecting enzyme activity

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

factor: temperature

A
  • at low temps, there is less movement of substrate and enzyme
    • less chance of molecules colliding
    • lower reaction rate
  • as temperature increases, the kinetic energy of the enzymes and substrate increase
    • more likely to collide and reactions are more likely to occur (as there is more movement)
  • above the optimum temp, the kinetic energy becomes too high
    • bonds that hold the shape of the enzyme begin to break
    • the enzyme starts to change shape, causing the active site to be disrupted and enzyme activity quickly starts to drop
    • the change in the shape of the active site of the enzyme is called denaturation
    • it is irreversible
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15
Q

factor: pH

A
  • if surrounding pH is too high or low from the optimal ph level, it can alter intra- and inter-molecular bonds of the active site and substrate complex
    • changes the shape of the active site
    • reduces or stops the function
  • when the ph is above or below the optimum range for enzyme, groups between the active site of enzyme and the substrate are no longer able to form a bond, causing enzyme activity to decline and eventually stop
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16
Q

factor: enzyme concentration

A

a higher concentration of enzyme will result in a higher rate of reaction, provided there is unlimited substrate

17
Q

factor: substrate concentration

A
  • a higher substrate concentration will result in a higher reaction rate, provided there is unlimited enzyme - to a point
  • after, adding substrate causes no significant change
  • with a finite amount of enzyme, the rate will increase until all the enzymes are working at their maximum rate
    • then the rate of reaction will plateau
18
Q

inhibitors

A
  • chemicals can also inhibit enzyme activity (called inhibitors)
  • they can be irreversible or reversible
  • of the reversible inhibitors, they can be competitive or non-competitive
    • reversible inhibitors bind noncovalently (weakly)
    • irreversible inhibitors bind covalently (strongly)
19
Q

competitive inhibition

A
  • the inhibitor has a similar shape to the substrate
    • blocks the formation of the enzyme-substrate complex
    • fewer substrates can bind to the enzyme
    • rate of reaction decreases
  • effects of competitive inhibitors reduces as substrate concentration increases
20
Q

non-competitive inhibition

A
  • the inhibitor binds to a region other than the active site → allosteric site
  • this changes the shape of the active site so the substrate has difficulties binding
21
Q

irreversible inhibitors

A
  • specific molecules can form a strong covalent bond with an enzyme at its active site
    • the normal substrate is permanently blocked from accessing the active site
    • are often poisons
  • eg. cyanide acts as an enzyme inhibitor for cellular respiration
  • penicillin acts as an enzyme inhibitor in bacteria
22
Q

limiting factor

A

A factor is referred to as limiting, if, in short supply, it restricts the rate of reaction

23
Q

what are cofactors

A

inorganic substances that are required for, or increase the rate of, catalysis

24
Q

equation for cellular respiration

A
  • Glucose + Oxygen → Water + Carbon Dioxide + 30-32ATP
  • C6H12O6 +6O2 → 6 CO 2 + 6 H 2 O + ATP