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PLANT > Enzymes (8) > Flashcards

Enzymes (8) Flashcards

1
Q

Life features? (4)

A

• Result of highly organized biochemical reactions.
• In vivo reactions are controlled by enzymes.
• Given correct conditions, reactions can occur in vitro without enzymes.
• Biochemical reactions controlled by enzymes.

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2
Q

How do enzymes speed up reactions?

A

They lower activation energy (Ea).

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3
Q

In vivo?

A

= in life.

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4
Q

In vitro?

A

= in test tube.

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5
Q

Activation energy?

A

= an energy barrier over which the molecules of a possible reaction must be raised in order for reaction to occur.

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6
Q

Indicate Ea in analogy.

A

Explain it.

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7
Q

Application of analogy in terms of molecules? (2)

A

• 2 different molecules must collide.
• 2 different molecules must overcome forces.

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8
Q

2 collisions that must occur 2 different molecules?

A

• Collision at correct angle.
• Collision with sufficient speed.

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9
Q

2 forces that the 2 different molecules must overcome?

A

• Repulsive forces.
• Existing chemical bonds.

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10
Q

Therefore, in the analogue, Ea is…?

A

= the amount of energy needed to overcome the repulsive forces & existing chemical bonds.

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11
Q

Relationship between Ea & likelihood of reaction taking place?

A

Increase Ea, Decrease likelihood of reaction taking place.

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12
Q

Methods of increasing reaction rate? (2)

A

• Heat.
• Catalyst.

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13
Q

In what systems is heat used to increase reaction rate?

A

Inorganic systems.

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14
Q

In what systems is a catalyst used to increase reaction rate?

A

Organic systems.

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15
Q

Catalyst?

A

= substance that decreases the Ea needed for reactions to occur.

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16
Q

How do catalysts decrease Ea?

A

By forming a temporary association with the reacting molecules.

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17
Q

Enzymes?

A

= organic catalysts.

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18
Q

What do enzymes do? (3)

A

• Allow biological reactions to occur in faster rates.
• Allow biological reactions to occur at a constant temperature.
• Allow specific biological reactions to occur at specific times/points (i.e., reactions can be regulated).

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19
Q

Enzyme structure? (2)

A

• Complex globular proteins (3⁰ structure).
• 3-D folding that produces a groove in the surface of the protein.

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20
Q

Which enzyme is found in every living organism?

A

Carbonic anhydrase.

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21
Q

What does Carbonic anhydrase do?

A

Breaks H2O & CO2 into carbonic acid.

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22
Q

Eg of Carbonic anhydrase in action?

A

Respiration.

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23
Q

Enzyme characteristics? (4)

A

• All are proteins.
• Can be used repeatedly.
• Present in very small quantities.
• Highly specific.

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24
Q

What can enzymes be used repeatedly?

A

Because they can combine with reacting molecules only briefly and are released unchanged.

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25
Q

Why are enzymes present in very small quantities?

A

Because they are efficient.

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26
Q

What do we mean when we say that enzymes are highly specific?

A

We mean that they only interact with specific molecules.

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27
Q

What do most enzymes need? (2)

A

• Non-protein substances.
• Low molecular weight substances.

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28
Q

Cofactor?

A

= ions.

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29
Q

Coenzyme?

A

= organic molecules.

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30
Q

Egs of Cofactors? (2)

A

• Ca2+.
• Mg2+.

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31
Q

Eg of Coenzymes?

A

NAD.

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32
Q

NAD stands for?

A

Nicotinamide Adenine Dinucleotide.

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33
Q

What do cofactors & coenzymes do?

A

Bind to an enzyme at a specific site (binding site).

34
Q

Result of adding a cofactor or coenzyme to the surface of enzyme?

A

Conformational change.

35
Q

Conformational change?

A

= alteration in the shape of an enzyme.

36
Q

What can a conformational change do? (2)

A

• Switch enzyme activity off.
• Switch enzyme activity on.

37
Q

What do Coenzymes do?

A

Act as electron acceptors (that usuallybind a proton) or as a pair of electrons.

38
Q

Difference between cofactors and coenzymes & enzymes?

A

● Cofactors & Coenzymes = they change
● Enzymes = don’t change.

39
Q

Why do enzymes need what they need?

A

To function.

40
Q

Enzyme nomenclature features back then? (2)

A

• Suffix of most enzymes is “ase”.
• Other enzymes names are not informative & inconvenient (Pepsin & Trypsin).

41
Q

Enzyme naming system systemic name structure now?

A

1st name = Donating molecule.
2nd name = Receiving Molecule.
3rd name = Tells you what is happening.

42
Q

Components of enzyme naming system? (3)

A

• Common name.
• Systemic name.
• Enzyme no.

43
Q

Eg of enzyme naming system?

A

ATP+Creatine—>ADP + phosphocreatine

● Common enzyme name
= Creatine kinase.

● Systemic name
= ATP creatine phosphotransferase.

● Enzyme no.
= EC 2:7:3:2.

44
Q

Enzyme classes? (6)

A

• Oxido-Reductases.
• Transferases.
• Lyases.
• Hydrolases.
• Isomerases.
• Ligases & Synthetases.

45
Q

Oxido-Reductases?

A

= removal & addition of electrons or electrons & H2.

46
Q

Transferases?

A

= the transfer of functional groups.

47
Q

Lyases?

A

= the formation of double bonds by elimination of a chemical group.

48
Q

Hydrolases?

A

= the breakage of chemical bonds by the addition or removal of elements of a molecule of water.

49
Q

Isomerase?

A

= rearrangement of the atoms of a molecule.

50
Q

Ligases & Synthetases?

A

= the formation of chemical bonds using ATP as an energy source.

51
Q

Egs of Oxido-Reductases? (3)

A

• Oxidases.
• Reductases.
• Dehydrogenases.

52
Q

Eg of Transferases?

A

Kinases.

53
Q

Kinases?

A

= transfer phosphate groups.

54
Q

Egs of Hydrolases? (2)

A

• Proteases.
• Ribonucleases.

55
Q

Proteases?

A

= hydrolysis of proteins.

56
Q

Ribonucleases?

A

= hydrolysis of RNA.

57
Q

Eg of Ligases & Synthetases?

A

Polymerases.

58
Q

Polymerases?

A

= linkage of monomers into a polymer.

59
Q

Enzyme assay?

A

= system to see if a particular enzyme is present.

60
Q

How is an enzyme’s presence detected? (2)

A

• Disappearance of the substrate.
• Appearance of the product.

61
Q

Process of enzyme assay?

A

Enzyme extract is incubated with the substrate under carefully controlled conditions & one must determine the correct conditions.

62
Q

What are these correct conditions? (4)

A

• Temperature.
• pH.
• Cofactors.
• Ionic strength.

63
Q

Buffer components? (3)

A

• pH.
• Cofactors.
• Ionic strength.

64
Q

Ionic strength?

A

=

65
Q

Eg of Enzyme assay?

A

The detection of protease.

66
Q

Explain eg of enzyme assay?

A

● Test tube where you add an enzyme extract, protein & buffer components.

● Incubate the above at the correct temperature.

67
Q

What do we measure in the enzyme assay eg? (2)

A

• Decrease in protein concentration.
• Increase in aa concentration.

68
Q

Why do we need controls in an experiment?

A

To prove that the observed/measured changes are due to enzyme activity.

69
Q

Egs of controls in experiments? (2)

A

• No enzyme.
• Denatured enzyme.

70
Q

Graphs on pH effects on enzyme activity what to note? (3)

A

• 4 graphs.
• Optimal pH.
• Amount of H+ ions.

71
Q

Relationship between pH & H+ ions present?

A

Low pH, More H+ ions.

72
Q

Effect of temperature on enzymes? (3)

A

● High temperatures
= denaturing of protein (breaking peptide bonds of protein)/cooking the enzyme.

● Optimal temperature
= enzyme activity at its best.

● Low temperatures
= physical destruction to protein.

73
Q

Allosteric enzymes role?

A

= responsible for the regulation of enzyme activity according to the requirements of the cell or organism.

74
Q

Eg of Allosteric enzyme? (2)

A

• Threonine deaminase.

75
Q

Common amino acids in protein synthesis? (2)

A

• Threonine.
• Isoleucine.

76
Q

Threonine deaminase features? (2)

A

• Does the switching on & switching off of Isoleucine.
• Sensitive to the concentration of Isoleucine.

77
Q

Can Isoleucine be converted back to Threonine deaminase?

A

Yes, as all reactions are reversible.

78
Q

Pathway of Threonine producing Isoleucine? (6)

A

Threonine.
| (E1- Threonine deaminase)
Product 1
| (E2)
Product 2
| (E3)
Product 3
| (E4)
Product 4
| (E5)
Isoleucine.

79
Q

What happens if cell nolonger requires Isoleucine?

A

The Isoleucine concentration continues to increase until Isoleucine sends feedback to Threonine deaminase to be switched off. Then Isoleucine concentration decreases.

80
Q

How does Isoleucine notify Threonine deaminase that it needs to be switched off?

A

Isoleucine binds on the Allosteric site to signal that it needs to be switched off as the cell is not using it. Isoleucine binds & its production stops.

81
Q

Why isn’t heat used in Organic systems? (2)

A

• Heat would trigger all the reactions to occur at the same time whereas in biological systems only specific reactions are required at specific times.

• Heat would denature/destroy the biological molecules.

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