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PMP-101 > Enzymes and Catalysis > Flashcards

Enzymes and Catalysis Flashcards

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1
Q

What are proteins?

A
  • Polymers
  • Linked together by peptide bonds
  • Arranged in 3D structural hierarchy
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2
Q

Tertiary structure

A

single polypeptide chain

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3
Q

quaternary structure

A

multiple polypeptide chains

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4
Q

made up of monomers:

A

acid amino
= determines 3D structure - depends on sequence of a.a

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5
Q

Enzymes

A

Biological catalysts that speed up enzymatic/ chemical reactions

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6
Q

which organisms are enzymes present?

A

Present in EVERY chemical reaction in EVERY organism

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7
Q

What are proteins made out of?

A

Proteins
(except for catalytic RNA’s - ribozymes)

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8
Q

Single enzymes

A

single polypeptide chain

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9
Q

Allosteric and multifunctional enzymes

A

complex - more of subunits / multiple polypeptide chains

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10
Q

What determines on how good catalytic activity?

A

the native folding of protein

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11
Q

What are the properties of enzymes?

A
  • specific for substrates
  • catalytic power = fast
  • Efficient. not altered after reaction (stays the same shape and size)
  • can be regulated
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12
Q

What is substrate specificity?

A
  • Ability of the enzyme to specifically recognise the proper substate (reactant)
  • Molecular recognition mechanism - based on structural complementary
  • substrate bind to specific region of enzyme - ACTIVE SITE
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13
Q

1st step of enzymatic catalysis

A

substrate-complex (E-S)

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14
Q

Lock and key model

A

Enzyme fits PERFECTLY into substrate

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15
Q

Induced fit

A
  • Substrate is NOT exactly complementary to active site SFTR binding
  • Conformational change occurs to allow better fit between active fit and substrate (hand in glove)
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16
Q

What is the active site? Where?

A
  • 3D pocket where substrate binds to
  • Small region of enzyme (10-20%)
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17
Q

What is the enzyme COMPOSED of?

A
  1. SUBSTRATE BINDING SITE
  2. CATALYTIC SITE
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18
Q

SUBSTRATE BINDING SITE

A
  • A.a side chains interact with substrate
  • Interactions that orientate the substate within the active site
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19
Q

CATALYTIC SITE

A
  • A.a that performs or catalyses the reaction
  • The correct folding of enzyme is required
    S-E binding alters the structure of the substrate to promote the formation of the transition state
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20
Q

Catalytic power..

A

Increase the rate of chemical reaction

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21
Q

How many times can rate of reaction increase with the presence of enzyme?

A

range: 10^6&raquo_space; 10^17

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22
Q

For start of reaction - energy is required. What’s this called?

A

Activation energy

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23
Q

Define activation energy

A

the minimum quantity of energy which the reacting species must possess in order to undergo a specified reaction

24
Q

Lower the activation energy…

A

faster the rate of reaction

25
Q

Does enzyme have an affect on the equilibrium of reactions?

A

No - no affect

26
Q

Efficiency and reusability?

A
  • unaffected by reaction which they catalyse
  • can be reused
    -active in LOW concentrations
27
Q

Conditions that affect enzyme functions:

A
  1. Temp
  2. Ionic condition
  3. pH
  4. Substate concentration
  5. Presence of inhibitors
28
Q

Temp and enzymatic activity

A
  • ^ temp = higher the rate of reaction
  • Usually 37C in humans (some archae - extremophiles its higher)
29
Q

Denturation

A

Loss of native folding in protein - active side no longer matches the substrate = loss of catalytic activity

30
Q

pH and enzymatic activity

A
  • most active optimum pH
31
Q

Optimum pH in the body

A
  • Small intensine enzymes : 7.5
  • Stomach enzymes : 1.5
  • Digestive lysosomal enzymes : 4-5
32
Q

when is structure disturbed by pH

A

in very low or very high pH as tertiary structure is disturbed

33
Q

Constant concentration of enzyme + increase in substrate

A

Concentration will cause increase in enzyme activity up to the point where enzyme is SATURATED with the substrate
WILL NOT change rate of reaction!!!

34
Q

Saturated meaning:

A

enzymes has reached their maximum activity (steady rate) and Maximum rate of reaction (Vmax)

35
Q

Reaction rate

A

ONLY measures on how rapidly the enzyme can process the substrate

36
Q

What is kinetics

A

the study of reaction rates

37
Q

Km

A

concentration of substrate at which reaction rate is half-maximal

38
Q

Higher Km

A

-weaker binding

39
Q

Lower Km

A

-stronger binding

40
Q

Competitive inhibitors

A

Competing with substrate by binding at active side and blocking it

(effect can be reversible or irreversible (covalent bonds)

41
Q

Non-competitive inhibitors

A

Bind into allosteric site on enzyme (NOT active site)

-Cause conformational change in enzyme and block of the catalytic activity / active site changes in shape
-Effect is reversible (usually)

42
Q

Enzyme cofactors

A

additional components - provide active site REACTIVE GROUPS
they are NOT substrates

43
Q

Coenzymes

A
  • Temporarily/ weakly bound to the enzyme
  • Altered during course of reaction and dissociate from the active site
44
Q

Examples of coenzymes:

A
  1. NAD+
  2. NADP+
45
Q

Protheic groups

A

-Tightly bound to enzyme = covalent bond
- must be regenerated each catalytic cycle

46
Q

examples of prothetic groups

A
  • HAEM (in haemoglobin) for oxygen REDOX reactions
  • FAD in REDOX reactions
  • VITAMIN B7 or Biotin = carboxylse enzymes
47
Q

HOLOENZYME

A

Complete catalytically-active enzyme together with its cofactor

48
Q

APONZYME (not active)

A

Protein part of enzyme on its own without its cofactor

49
Q

7 major groups of the international Union of Biochemistry

A
  1. Oxidoreductases
  2. Transferases
  3. Hydrolases
  4. Lyases
  5. Isomerase
  6. Ligases
  7. Translocases
50
Q

ENZYME Class 1 Oxidoreductases

A

Catalyse REDOX reactions

51
Q

ENZYME Class 2 Transferases

A

Catalyse functional group transfer reactions

52
Q

ENZYME Class 3 Hydrolases

A

Catalyse hydrolasis reactions (transfer functional groups to water by breaking down of a bond)

53
Q

ENZYME Class 4 Lyases

A
  • Catalyse the cleavage of C-C, C-O, C-N or other bonds by elimination, leaving double bonds or rings, or addition of groups to double bonds
  • They catalyse the breaking of a chemical bond between two parts of a molecule (other than hydrolytic or oxidative bond breaking)
54
Q

ENZYME Class 5 Isomerases

A

Catalyse transfer of groups within molecules to yield isomeric forms

55
Q

ENZYME Class 6 Ligases

A
  • The joining ligation of two large molecules by forming a new chemical bond with the release energy
56
Q

ENZYME Class 7 translocases

A
  • Movement of molecules or ions across membranes or their separation within membranes

PMP-101 (53 decks)

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