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BIOB111 > Enzymes and Co Enzymes > Flashcards

Enzymes and Co Enzymes Flashcards

1
Q

Is an enzyme a protein, carb or lipid?

A

Protein (globular proteins and a few enzymes are made of RNA)

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2
Q

What are enzymes’ purpose?

A

Catalyse biochemical reactions or speed up the rate of a chemical reaction.

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3
Q

Are thousands of enzymes located in each cell of the human body?

A

Yes.

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4
Q

Define simple enzymes.

A

Protein only enzyme that facilitates a chemical reaction.

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5
Q

Define coenzyme.

A

Compound derived from a vitamin (e.g. NAD+) that assists an enzyme in facilitating a chemical reaction.

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6
Q

Define Cofactor.

A

Metal ion (e.g. Mg2+) that assists an enzyme in facilitating a chemical reaction.

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7
Q

Define Apoenzyme.

A

Protein only part of an enzyme (e.g. isocitrate dehydrogenase) that requires an additional coenzyme to facilitate a chemical reaction (not functional alone).

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8
Q

Define Holoenzyme.

A

Combination of the apoenzyme and coenzyme which together facilitating a chemical reaction (functional).

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9
Q

Give an example of a Substrate/Chemical Group Prefix enzyme.

A

Urease acts on urea

Sucrase acts on sucrose

Lipase acts on lipids

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10
Q

Give an example of a Reaction Catalysed Prefix.

A

Oxidase - oxidation reaction

Hydrolase - hydrolysis

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11
Q

What are the six major classes of enzymes?

A
  1. Oxidoreductases
  2. Transferase
  3. Hydrolase
  4. Lyase
  5. Isomerase - convert one isomer of an organic molecule to another
  6. Ligase
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12
Q

What does the enzyme class Oxidoreductases do?

A

Oxidation-reduction enzymes

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13
Q

What does the enzyme class Transferase do?

A

Transfer functional groups

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14
Q

What does the enzyme class Hydrolase do?

A

Causes hydrolysis in reactions

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15
Q

What does the enzyme class Lyase do?

A

Addition or removal of groups

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16
Q

What does the enzyme class Isomerase do?

A

Convert one isomer of an organic molecule to another

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17
Q

What does the enzyme class Ligase do?

A

Bond formation with the participation of ATP. Connects two DNA molecules together.

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18
Q

What is an active sight on an enzyme?

A

Specific portion of an enzyme’s location where the substrate binds while it undergoes a chemical reaction

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19
Q

What is the function of an enzyme?

A
  1. Reduce the activation energy of a chemical reaction

2. Lower activation energy means that the rate of the chemical reaction increases

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20
Q

What happens in the course of an enzyme catalysed chemical reaction?

A
  1. Substrate (reactant) binds to the active site of the enzyme creating the enzyme subrate complex.
  2. Substrate is converted to the product
  3. Product releases from the enzyme
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21
Q

Why is it that each different chemical reaction requires a different enzyme? Hint: think about the
structure (shape) of the enzyme and substrate.

A

Substrate - must have a specific shape to fit into the specific shape of the active site in the enzyme

Only specific substrates and enzymes fit together, which means a different enzyme is required to catalyse each different chemical reaction.

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22
Q

Explain the induced fit model of enzyme action by stating whether structural changes are required in
the enzyme in order to bind the substrate

A

Enzyme slightly changes the shape of it’s active site to accommodate the binding of a specific substrate.

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23
Q

Can an enzyme be used again once a product is released?

A

Yes

24
Q

What is a substrate?

A

the substance on which an enzyme acts.

25
Q

What forms the Enzyme-Substrate Complex?

A

Substrate will bind to the enzyme’s active site.

26
Q

What are the two key models of enzyme action?

A
  1. Lock and Key

2. Induced-fit

27
Q

What is the model of enzyme action where an enzyme active site and the substrate possess a specific complementary geometric shape that fit exactly into one another?

A

Lock and Key

28
Q

What are 4 features of the Lock and Key Model?

A
  1. The active site is fixed, with a rigid shape
  2. The substrate must fit exactly into the rigid enzyme
  3. Complementary shape and geometry between enzyme and substrate
  4. Upon completion of the chemical reaction, the products are released from the active site, so the next substrate molecule can bind
29
Q

What is the model of enzyme action where an active site allows for small changes in space to accommodate the substrate? Hint “hand in glove”

A

Induced-fit

30
Q

What are 3 features of the Induced-fit Model?

A
  1. Many enzymes are flexible and constantly change their shape
  2. The shape of the active site changes to accept and accommodate the substrate
  3. Conformation change in the enzyme’s active site to allow the substrate to bind
31
Q

Define absolute specificity of enzyme specificity.

A

An enzyme will catalyse a particular reaction for only one substrate.

32
Q

Define group specificity of enzyme specificity.

A

The enzyme will act only on similar substrates that have a specific functional group.

33
Q

Define linkage specificity of enzyme specificity.

A

The enzyme will act on a particular type of chemical bond, irrespective of the rest of the molecular structure.

34
Q

Define stereochemical specificity of enzyme specificity.

A

The enzyme can distinguish between stereoisomers.

35
Q

What are the four factors that affect enzyme activity?

A
  1. Temperature
  2. pH
  3. Substrate concentration (substrate)
  4. Enzyme concentration (enzyme)
36
Q

As temperature increases will more or less collisions occur? And will there be an increased or decreased reaction rate?

A

More collisions and an increased reaction rate.

37
Q

What is optimum temperature?

A

Where the enzymes exhibits maximum activity

38
Q

When there is excess heat, what occurs?

A

Inactivating and denaturing

39
Q

What is optimum pH?

A

Where enzymes exhibit maximum activity

40
Q

What is the usual ph range for enzymes?

A

7-7.5

41
Q

What is the ph range for the digestive enzymes Pepsin and Trypsin?

A

Pepsin (stomach) 2.0

Trypsin (SI) 8.0

42
Q

What is substrate concentration?

A

When an enzyme is kept constant and the substrate increases.

Substrate concentration increases until a point of saturation met where the reaction stays the same.

43
Q

What is enzyme concentration?

A

When a substrate is kept constant and the enzyme increases.

Reaction rate increases (greater the enzyme the greater the reaction rate).

44
Q

What is an enzyme inhibitor?

A

It is a substance that slows down or stops the normal catalytic function of an enzyme by binding to the enzyme.

45
Q

What are the three types of enzyme inhibition?

A
  1. Reversible competitive inhibition
  2. Reversible non-competitive inhibition
  3. Irreversible inhibition
46
Q

What is a Reversible Competitive Inhibition?

A

Resembles the substrate and competes with the substrate for binding to the active site of the enzyme.

It decreases or altogether stops enzyme activity.

47
Q

What is Reversible Noncompetitive Inhibition?

A

Decreases enzyme activity by binding to a site on the enzyme other than the active site.

It decreases enzyme activity.

48
Q

What is Irreversible Inhibition?

A

It inactivates an enzyme by binding to its active site by a strong covalent bond.

It permanently deactivates the enzyme.

49
Q

What are the two binding sites of Allosteric Enzymes? And what do they do?

A
  1. Active site: One bonding site for the substrate
  2. Regulatory site: Second binding site for a regulator molecule

Regulatory molecule

50
Q

What does a positive allosteric reaction do?

A

Up regulates. It allows for the substrate to bind to the active site.

51
Q

What does a negative allosteric reaction do?

A

Down regulates. It doesn’t allow the substrate to bind to the active site. Stops or decreases reaction.

52
Q

Describe Feedback Controls purpose.

A

Produces regulatory molecule.

There is a sequence of enzymatic reactions where a product is accumulated and binds to an allosteric site of one of the earlier reactions to inhibit activity.

53
Q

What are the three mechanisms of Allosteric enzyme regulation?

A
  1. Feedback Control
  2. Proteolytic Enzymes and Zymogens
  3. Covalent Modification of Enzymes
54
Q

Describe Proteolytic Enzymes and Zymogens purpose.

A

Production of an enzyme in an inactive form which are activated when required.

They catalyse the breaking of peptide bonds in proteins

55
Q

What is required for activation of Proteolytic Enzymes and Zymogens?

A

Activation of a zymogen requires the removal of a peptide fragment from its structure which affecting the active site.

56
Q

Describe Covalent Modification of Enzymes purpose.

A

Alters enzyme activity by covalently modifying the structure of the enzyme and adding/removing a group to/from the enzyme.

57
Q

What are the most common vitamins used as coenzymes?

A

Vitamin B

BIOB111 (3 decks)

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