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Intro BCH > Enzymes > Flashcards

Enzymes Flashcards

1
Q

All enzymes are proteins. True or false?

A

False, but almost all are

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2
Q

Which enzymes are not proteins?

A

Ribozymes - catalytic RNA molecules

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3
Q

The reactant in an enzyme catalyzed reaction is called…

A

…a substrate

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4
Q

What is the active site of an enzyme?

A

The small part of the molecule responsible for its catalytic action

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5
Q

Enzymes work by…

A

…changing the rate of a chemical reaction. They speed up metabolic reactions by reducing the activation energy needed for the uncatalyzed reaction.

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6
Q

Characteristics of enzymes

A
  • Chemically unaltered, equilibrium constant too
  • Operate under standard physiological conditions
  • High specificity
  • High catalytic efficiency
  • Form complexes
  • Reusable
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7
Q

Modes of enzyme action

A
  • Lock and key

- Induced fit

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8
Q

Lock and key enzyme action

A

Both enzyme and substrate have corresponding shapes that lets them fit

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9
Q

Induced fit model

A

Enzyme and substrate change shapes to produce fit

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10
Q

Factors affecting enzyme action

A

Temperature
pH
Concentration
Co-factors

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11
Q

Temperature and pH higher than the optimal value will lead to…

A

Denaturing of the enzyme

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12
Q

Optimal temperature for enzymes in the human body

A

37oc

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13
Q

Optimal pH for enzymes in the human body

A

~8

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14
Q

Effect of high temperature on enzyme

A

Shape change, midfolding and denaturing

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15
Q

What are co-factors?

A

Small organic, inorganic, metallo-organic molecules or metal ions required by some enzymes for activity

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16
Q

Examples of prosthetic co-factors

A

Heme in haemoglobin

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17
Q

What are prosthetic groups?

A

Co-factors that are tightly bound to enzymes and remain associated with then between reaction cycles.

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18
Q

What are co-substrates?

A

Weakly bound co-factors that can associate and dissociate between cycles, behaving like substrates.

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19
Q

Biotin (CE)

A

Carboxylation

20
Q

Cobalamin (CE)

A

Alkylation, intramolecular rearrangements and ribonucleotide reduction

21
Q

Acyl transfer

A

Co-enzyme A, Lipoic acid (CE)

22
Q

Flavin (CE)

A

Redox

23
Q

Nicotinamide co-enzymes

A

Redox

24
Q

Amino group transfer

A

Pyridoxal phosphate (CE)

25
Q

One carbon transfer

A

Tetrahydrofolate (folic acid) (CE)

26
Q

Aldehyde transfer

A

Thiamine pyrophosphate (CE)

27
Q

Sugar transfer

A

Uridine diphosphate (CE)

28
Q

Classes of enzymes

A

6 - OTHLIL

Oxidoreductases
Transferases
Hydrolases
Lyases 
Isomerases
Ligases
29
Q

Levels of enzyme specificity

A

Absolute - Just 1 substrate
Group - One group of substrate
Steroisomeric - One stereoisomer

30
Q

Oxidoreductases function and examples

A

Electron transfer or remove and addition of H atoms, eg alcohol dehydrogenase

31
Q

Transferase function and examples

A

Functional group transfer, eg hexokinase

32
Q

Hydrolase function and examples

A

Hydrolysis reactions, eg trypsin

33
Q

Lyases function and examples

A

Cleavage of bonds to form double bond, eg pyruvate decarboxylase

34
Q

Isomerases function and examples

A

Transfer of groups within molecules, isomerisation, eg Maleate isomerase

35
Q

Ligases or synthases function and examples

A

Bond formation, ATP hydrolysis, eg pyruvate carboxylases

36
Q

Parts of a protein enzyme structure

A

Active site

Allosteric site

37
Q

Organic and inorganic co-enzymes are called…

A

Co-enzymes and Activators

38
Q

Apoenzyme

A

No covalently bound prosthetic group

39
Q

Holoenzyme

A

Apoenzyme + Prosthetic group

40
Q

Proenzyme or Zymogens

A

Require enzymes to lyse portions of their peptide bonds for activation

41
Q

Examples of proenzymes

A

Angiotensin, Chemotrypsin, Pepsinogen

42
Q

Isoenzymes

A

Enzymes that exist in different forms but can be differentiated based on solubility, activation, electrophoretic mobility, etc

43
Q

Characteristics of isoenzymes

A
  • Catalyze same reaction but with different potencies
  • Tissue specificity
  • Multiple genetic origin
44
Q

Isoforms

A

Different form of an enzyme resulting from posttranscriptional modifications but same genetic origin.

45
Q

Where is a substrate oriented for catalysis?

A

The binding site of the active site

46
Q

Effects of residues at binding sites

A
  • H-bond formation
  • Hydrophobic interactions
  • Temporart covalent interactions (Van Dar Waals)
47
Q

Active sites ate affected by environmental conditions. True or false?

A

True

Intro BCH (4 decks)

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