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Alevel Biology OCR > 2.1.4 - Enzymes > Flashcards

2.1.4 - Enzymes Flashcards

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1
Q

What are enzymes?

A

biological catalysts

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2
Q

What properties do all enzymes have?

A
  • are globular proteins
  • specific (only have one substrate)
  • have an active site
  • affected by temperature and pH
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3
Q

What are anabolic reactions?

A

reactions that construct molecules from smaller units

  • require energy
    eg. protein synthesis, building biological molecules
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4
Q

What are catabolic reactions?

A

reactions that break molecules down into smaller units

  • release energy
    eg. digestion, respiration
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5
Q

What are intracellular enzymes?

A

enzymes that react within a cell

eg. catalase, DNA polymerase

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6
Q

What are extracellular enzymes?

A

enzymes released from cells, which work outside of cells

eg. amylase, trypsin

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7
Q

Describe the lock and key hypothesis

A
  • active site is complementary to a specific substrate
  • when substrate binds to active site, enzyme-substrate complex is formed
  • enzyme-product complex is formed after the substrate has reacted and products have formed
  • enzyme holds substrate so that the right atom groups are close enough to react
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8
Q

Describe the induced fit hypothesis

A
  • when the substrate enters, the active site changes shape slightly
  • initial interactions are weak but they change the enzyme’s tertiary structure, which strengthens the interactions and puts a strain on the substrate
  • this weakens bonds and therefore lowers the activation energy
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9
Q

What factors affect enzyme action?

A
  • temperature
  • pH
  • substrate concentration
  • enzyme concentration
  • presence of inhibitors
  • presence of cofactors
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10
Q

How does an increase in temperature affect the rate of enzyme action?

A

-increase in temp increases kinetic energy
-enzymes and substrates move faster
-active site and substrate collide more frequently
-more enzyme-substrate complexes
increases rate of reaction

  • past 38°C the rate decreases
  • enzyme denatures
  • active site no longer a complementary shape to substrate
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11
Q

What is the temperature coefficient?

A

Q10
for enzyme controlled reactions, the rate of reaction doubles with each 10°C increase
∴ Q10 = 2

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12
Q

What is denaturing (of an enzyme)?

A

change in tertiary structure of an enzyme (because bonds are broken)
the active site irreversibly changes shape and no longer has a complementary shape to the substrate

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13
Q

What is an optimum pH (for enzymes)?

A

the pH (/certain concentration of hydrogen ions) where the enzyme’s active site remains the correct shape

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14
Q

Why do too acidic/too alkali conditions affect enzyme action?

A
  • H+ ions interact with polar R-groups of amino acids
  • when the concentration of H+ (pH) changes, the degree of interactions between R-groups change
  • the more H+ ions (low pH) present, the less R groups can interact
  • bonds break and the active site changes shape
  • the less H+ ions (high pH) present, the more R groups can interact
  • more bonds form and the active site changes shape
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15
Q

What is an enzyme inhibitor?

A

a substance/molecule that slows down the rate of an enzyme-controlled reaction by affecting the enzyme somehow (usually by causing the active site to change in some way)

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16
Q

Why do enzymes need to be inhibited?

A
  • to regulate enzyme-controlled reactions

- to regulate amount of products produced

17
Q

What are the two types of enzyme inhibitors?

A

competitive inhibitors

non-competitive inhibitors

18
Q

What is a competitive inhibitor?

A

a molecule that has a similar shape to the substrate so can fit into the enzyme’s active site
-blocks the substrate from entering the active site

19
Q

How does a competitive inhibitor affect the rate of reaction?

A
  • reduces rate of reaction (because it reduces how many substrates can bind to the active sites)
  • does not change Vmax (takes longer to get there but does not reduce it -if the substrate concentration is increased enough there will be more substrates than inhibitors)
20
Q

What is a non-competitive inhibitor?

A

a molecule that binds to the allosteric site on an an enzyme (location other than the active site)
-causes the tertiary structure of the enzyme to change so changes the shape of the active site, meaning the active site no longer has a complementary shape to the substrate

21
Q

How does a non-competitive inhibitor affect the rate of reaction?

A
  • reduces rate of reaction and causes rate to plateau sooner
  • lowers Vmax
  • increasing enzyme or substrate concentration won’t affect the inhibitor’s affect
  • level or inhibitation depends on number of inhibitors
22
Q

What is end product inhibitation?

A

when the product of a reaction acts as an inhibitor to the enzyme that produced it
-are reversible + non-competitive

23
Q

Why can end product inhibitation be a good thing?

A
  • excess products aren’t made

- resources aren’t wasted

24
Q

What are enzyme cofactors?

A

non-protein components on enzymes that help them catalase reactions

25
Q

How are enzyme cofactors obtained?

A

from diet

  • inorganic cofactors are from minerals (eg. iron, zinc, calcium)
  • coenzymes are from vitamins (eg. vitamin B3 and B5)
26
Q

What are coenzymes?

A

cofactors that are organic molecules

27
Q

What is the cofactor for amylase?

A

chlorine ions (Cl-)

28
Q

What is the prosthetic group of carbonic anhydrase?

A

zinc ions (Zn2+)

29
Q

What are precursor enzymes?

A

enzymes produced in inactive form

-they need to undergo a change in shape/tertiary structure to be activtaed

30
Q

Why are some enzymes produced in inactive form?

A
  • they only need to be active in certain conditions

- they can damage cells/tissues

31
Q

What is an apoenzyme?

A

precursor enzyme before cofactor is added

32
Q

What is a holoenzyme?

A

precursor enzyme with added cofactor

33
Q

How is a holoenzyme made?

A

apoenzyme + cofactor -> holoenzyme

34
Q

What are zymogens/proenzymes?

A

precursor enzymes that are made active by another enzyme, a change in temperature or a change in pH

35
Q

How is inactive pepsinogen activated?

A

by acidic conditions (low pH) in stomach

  • transforms into active pepsin (which digests proteins in stomach)
  • as activation only occurs in acidic conditions, the rest of the body tissues are safe from being digested
36
Q

What is a biological catalyst?

A

a protein used in metabolism that alters the rate of reaction (by lowering the activation energy) without being used up or changed

Alevel Biology OCR (26 decks)

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