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1. Foundations of Medicine PoNF > Enzymes > Flashcards

Enzymes Flashcards

1
Q

What is an enzyme

A

Protien that catalyses chemical reactions without itself being destroyed/altered - seek to lower the Ea

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2
Q

What is different with enzyme catalysed reactions compared to chemical catlysts

A

Can be regulated

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3
Q

Subvstrate

A

Reactant in catalysed reaction

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4
Q

Active site

A

Part of enxyme that binds to substrate to form E-S complex

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5
Q

product

A

Substance produced by enzyme-catalysed conversion of substrate

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6
Q

Cofactor

A

non-protien component needed for the reaction (e.g. magnesium)

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7
Q

Coenzyme

A

Heat-stable substance which can aid enzyme reactions

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8
Q

Isoenzyme

A

enzymes that catalyse the same reaction but vary in structure and other biochemical properties

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9
Q

Activation energy

A

Energy needed for the reaction to proceed

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10
Q

How do enzymes inc the rate of reaction

A

by lowering the Ea

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11
Q

How do enxymes lower the Ea (3)

A
  • Entropy reduction - Enzymes force the substate to be correctly orientated by binding them in the formation they need to be in for the reaction to proceed
  • Desolvation - weak bonds between S and E essentially replace most or all of the H-bonds between substrate and aqueous solution
  • Induced fit - conformational changes occur in the protien structure where the substrate binds
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12
Q

basic enzyme reaction

A
  1. substrate enters active site of enzyme
  2. forms an enzyme-substrate complex, enzyme changes shape slightly as substrate binds (induced fit)
  3. forms an enzyme-product complex
  4. products leave active site of enzyme
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13
Q

Michaelis-Menton plot

A

V0= Vmax [S]/Km

V0= initial reaction velocity
Vmax= maximum reaction velocity
[S]= substrate concentration
Km= the substrate concentration when the reaction is at ½ the maximum velocity (Vmax)

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14
Q

Michaelis-menton plot diagram

A

look one up

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15
Q

What does Km measure

A

Specificity of enzyme for substrate

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16
Q

What does a low/high Km value mean?

A
  • Low = good fit
  • High = poor fit (takes lots of substrate to get to 1/2Vmax)
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17
Q

What does Vmax measure

A

how fast a reaction is proceeding when the enzyme is saturated with substrate

18
Q

What can affect enzyme reactions

A
  • Enzyme concentration - inc, inc rate
  • Substrate concentration
  • Temp
  • pH
  • Inhibitors (competitive/non-competitive)
19
Q

What are competitive inhibitors

A

Inhibitor binds to AC of enzyme and prevents the substrate from binding

20
Q

What happens to Vmax and Km with competitive inhibition

A
  • Vmax = unchanged
  • Km = inc because it takes more substrate to overcome the inhibition
21
Q

What is non-competitive inhibiton

A

Inhibitor binds to a secondaty site on the enzyme which changes the shape of the AS and prevents the substrate from binding

22
Q

What happens to Vmax/Km during non-competitive inhibition

A
  • Vmax = decreased
  • Km = remains the same
23
Q

Why measure enzymes

A
  • Detection of suspected disease at pre-clinical stage
  • Confirmation of suspected disease and assessing severity
  • Localisation of disease to organs
  • Characterisation of organ pathology
  • Assessing the response to therapy
  • Organ function assessment
  • Assessing genetic susceptibility to drug side effects
  • Detection of inherited metabolic disease
  • Detection of vitamin deficiencies**
24
Q

Factors to determine enzyme activity in serum/plasma

A
  • age
  • gender
  • pregnancy
  • race
  • time of day
  • genetics
  • drugs
  • disease process, progress and treatment e.g. surgery
25
Q

Serum enzyme concentrations

A

Although there are some enzymes secreted from cells, serum E conc generally Low and only rise when there is damahe to cells and release of contents

26
Q

what is the release of enzymes from cells triggered by - factors to determine E activity in serum/plasma

A
  • hypoxia
  • cellular damage
  • physical damage
  • immune disorders
  • microbiological agents
  • genetic defects
  • nutritional disorders
27
Q

hypoxia

A

Loss of O2 supply due to occlusion, inadequate oxygenation, or O2 carrying capacity

28
Q

What could cause cellular damage

A

chemicals/drugs

29
Q

What could physical damage include

A

trauma, surgery, burns, radiation…

30
Q

Give some examples of immune disorders

A

anaphylaxis, automimmune diseases

31
Q

What could microbiological agents include

A

bacteria, viruses, fungi, protozoa, helminthhs

32
Q

WHat could nutritional disorders include

A

protien-calorie, vitiman, mineral deficiencies

33
Q

How do we analyse enzymes in the lab

A
  • Rate of an enzyme-catalysed reaction is directly proportional to the amount of enzyme present
  • Progress of conversion of the substrate to product is monitored:
    Fixed-time - at an end-point
    Continuous - throughout
  • Often measurement of an end product using spectrophotometry - coloured end product
  • Electrophoresis - to determine type (origin)
34
Q

What are some problems with enzyme measurement

A
  • Not specific i.e. can be found in more than one tissue in the body.
  • Particular requirements - temperature, pH etc.
  • Assays must be optimised to conditions E require
35
Q

In what clinical situations are enzymes used - clinical diagnosis

A
  • tissue damage
  • Determine origin of affected tissue
  • Disease related to enzyme defects
36
Q

What are some facts/conditions of enzyme use clinically

A
  • often not specific
  • need particular conditions for measurement
37
Q

Why is enzyme activity measured in a clinical setting

A

enzyme assays are valuable for diagnosis of several diseases in clinical settings due to their high sensitivity, specificity, and rapid response.

38
Q

what factors can influence enzyme activity in samples

A

temperature, pH, enzyme concentration, substrate concentration, and the presence

39
Q

Michaelis constant definition

A

the concentration of substrate that is transported at half the maximal velocity (Vmax) of transport; a measure of the affinity of the transporter for its substrate.

40
Q

WHat does knowledge of the michaelis constant allow to be deduced about the nature of the catlysed reaction

A

A measure of how well a substrate complexes with a given enzyme, otherwise known as its binding affinity.

1. Foundations of Medicine PoNF (22 decks)

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