2.1.4 - Enzymes Flashcards

1
Q

What is an enzyme ?

A

A biological catalyst that increase the rate of chemical reactions without being used up

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2
Q

Define the term ‘Metabolism’ ?

A

Metabolism - All the chemical reactions that occur within a living organism

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3
Q

Define the term ‘Anabolic reaction’ ?

A

Anabolic reactions - The building of large molecules from smaller molecules

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4
Q

Name an example of enzymes being involved in anabolic reactions ?

A

The synthesis of large polymer-based components in cells

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5
Q

Define the term ‘Catabolic reactions’ ?

A

Catabolic reactions - The breakdown of larger molecules into smaller molecules

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6
Q

Name an example of enzymes being involved in catabolic reactions ?

A

The breakdown of glucose to release energy

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7
Q

Define the term ‘intercellular enzymes’ ?

A

Intercellular enzymes - Enzymes that catalyse reactions inside the ell that produced them

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8
Q

Name an example of an intercellular enzyme ?

A

Catalase - An intercellular enzyme that catalyses the breakdown of hydrogen peroxide into oxygen and water. Hydrogen peroxide is a toxic product of many metabolic pathways therefore preventing its accumulation.

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9
Q

Define the term ‘Extracellular enzymes’ ?

A

Extracellular enzyme - Enzymes that catalyse reactions outside the cell that produced them

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10
Q

What is the role of extracellular enzymes ?

A
  • Nutrients are often in the form of polymers and therefore too large to enter cell via the cell surface membrane
  • Extracellular enzymes are used to break down the large nutrient molecules into smaller molecules so they can be absorbed by the cell
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11
Q

Name examples of an extracellular enzymes ?

A
  • Amylase
  • Trypsin
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12
Q

Explain how amylase acts as an extracellular enzyme ?

A

Amylase - It is an extracurricular enzyme that breakdown of starch to maltose.
- Maltase catalyses breakdown of maltose to glucose which os then small enough to be absorbed by cells lining the digestive system and into the bloodstream

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13
Q

Explain how trypsin acts as an extracellular enzyme ?

A
  • Trypsin is a protease that catalyses the digestion of proteins into smaller peptides which can then be broken down into amino acids by other proteases
  • Amino acids are then absorbed by cells lining digestive system and then absorbed into bloodstream
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14
Q

Define the term ‘Activation energy’ ?

A

Activation energy - The minimum amount of energy required for a chemical reaction to occur

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15
Q

How do enzymes function ?

A
  • Many different enzymes are produced by organisms, each enzyme catalysing one biological reaction making them specific ( specificity of enzyme )
  • Enzymes help the molecules collide, lowering the activation energy required by the reaction and producing an alternative reaction pathway
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16
Q

Define the term ‘Turnover number’ ?

A

Turnover number : The number of reactions that an enzyme molecule can catalyse per second

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17
Q

What are the two models for how enzymes function ?

A
  • Lock and key hypothesis
  • Induced-fit hypothesis
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18
Q

Explain the lock and key hypothesis ?

A
  • The tertiary structure of the enzyme determines the enzyme’s and enzyme’s active site’s shape which is complementary to a specific substrate molecule
  • Lock and key hypothesis says that like only a specific key will fit into a lock / only a specific substrate will ‘fit’ in active site of enzyme
  • When the substrate binds to the active site of an enzyme, an enzyme-substrate complex forms. Substrate then react leading to formation of product in enzyme-product complex which are then released leaving the enzyme to react is subsequent reactions
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19
Q

Explain the induced-fit hypothesis ?

A
  • The induced-fit hypothesis suggests the enzyme’s active site changes shape slightly when reacting with substrate to accommodate for the substrate
  • When a substrate binds with active site of an enzyme, this induces a change in the enzymes tertiary structure so it becomes complementary to substrate
  • This can put strain on substrate and weaken bonds in substrate lowering the activation energy of the reaction
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20
Q

What are the factors affecting enzyme activity ?

A
  • Temperature
  • pH
  • Substance concentration
  • Inhibitors
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21
Q

Explain the affect of temperature ( higher ) on enzyme activity ?

A
  • As the temperature increases, the kinetic energy of particles increases causing the particles to move faster and collide more frequently per time period
  • This means/ causes more frequent successful collisions between substrate and enzyme leading to more enzyme-substrate complexes forming leading to an increased rate of reaction
22
Q

Explain the effect of temperature ( lower ) on enzyme activity ?

A
  • As the temperature decreases, the kinetic energy of molecules decreases
  • This causes substrate and enzyme molecules to collide less often and collide successfully less often per time period
  • This results in less enzyme-substrate complexes forming causing the rate of the reaction to decrease
23
Q

Explain the affect of extreme temperature on enzyme activity ?

A
  • Enzymes are globular proteins and therefore their structure, therefore shape is affected by temperature
  • As the temperature increases, bonds holding the protein together vibrate more until the bonds break
  • This results in the change in the precise tertiary structure of the protein causing enzyme to change shape, active site to change shape and no longer remain complementary to substrate so called denatured
  • Substrate can no longer bind to the enzymes active site so enzyme can no longer function
24
Q

What is the temperature coefficient ?

A

The temperature coefficient is measure of how much the rate of reaction increases with a 10oC rise in temperature

25
Q

What is the symbol of the temperature coefficient ?

A

Qv10

26
Q

What is the temperature coefficient of enzyme-controlled reactions ?

A

For enzyme-controlled reactions, the rare of reaction doubles as the temperature increases by 10oC ( Qv10 = 2 )

27
Q

Explain the affect of pH on enzyme activity ?

A
  • When the pH is optimal, enzymes will maintain their specific shape and function optimally
  • When the pH changes significantly the enzyme will denature
28
Q

Explain the affect of high pH on enzyme activity ?

A

This leads to enzyme becoming denatured

29
Q

Explain the affect of low pH on enzyme activity ?

A
  • A low pH means more H+ ions are present
  • This means less R-groups of amino acids are able to interact with one another leading to ionic/hydrogen bonds breaking in the tertiary structure causing the tertiary structure to change and therefore shape of the enzyme to change
30
Q

Explain the affect of substrate concentration on enzyme activity ?

A
  • When the substrate concentration increases, the number of collisions between substrates and enzymes active site increases per time period
  • This causes the rate of formation of enzyme-complexes to increase, causing rate to increase
  • This continues till all enzymes active site’s have become saturated and the rate reaches its max ( Vmax )
  • Substrate concentration will no longer have any affect
31
Q

Explain the affect of enzyme concentration on enzyme activity ?

A
  • As the enzyme concentration increases, the number of collisions between substrates and enzymes active site increases per time period
  • This causes the rate of formation of enzyme-complexes to increase, causing rate to increase
32
Q

How can the Vmax be increased once substrate concentration no longer has an affect ?

A

Vmax can be increased by increasing enzyme concentration so more active sites are available leading to formation of enzyme-substrate complexes at a faster rate or by increasing temperature

33
Q

Define the term ‘Inhibitors’ ?

A

Inhibitors - Molecules that prevent enzymes from functioning normally/ catalysing chemical reactions

34
Q

What are the two type of inhibitors ?

A
  • Competitive inhibitors
  • Non-competitive inhibitors
35
Q

Explain how competitive inhibitors function ?

A
  • Competitive inhibitors are a similar shape to the substrate that binds to the specific active site of an enzyme
  • Competitive inhibitors will bind to active site of enzyme and prevent substance molecules from binding to specific active site reducing. number of substrates binding to enzymes, enzyme-substrate complexes forming and reducing rate of reaction
  • Enzyme has been inhibited
36
Q

Explain the effect of competitive inhibitors on the rate of enzyme activity ?

A
  • They reduce the rate of reaction but not Vmax
  • This can be combated by increasing substrate concentration increasing number of substrates and therefore number of enzyme-substrate complexes forming till Vmax is reached
37
Q

Explain why the effect of competitive inhibitors is reversible ?

A

Most competitive inhibitors only bind to active site temporarily, so their effect is reversible

38
Q

Name examples of competitive inhibitors ?

A
  • Statins
  • Aspirin
39
Q

Explain how non-competitive inhibitors function ?

A
  • Non-competitve inhibitors are molecules that kind to the enzyme at a point other than the active site ( allosteric site )
  • This causes the enzymes tertiary structure to change and therefore its active site meaning it is no longer complementary to the substrate so it cannot bind to enzyme
  • The enzyme can no longer carry out its function and is inhibited
40
Q

Explain the effect of non-competitive inhibitors on the rate of enzyme activity ?

A

They reduce the rate of the reaction as more active sites become unavailable

41
Q

What happens when the upstart concentration is increased in the presses of a non-competitive inhibitor ?

A

Unlike for competitive inhibitors, the rate for the reaction will not continue to increase as the concentration of substrates increases

42
Q

Explain why the effect of non-competitive inhibitors is non-reversible ?

A

The structure of enzyme is permanently altered so increasing enzyme/ substrate concentration does not combat effect so non-reversible

43
Q

Name examples of non-competitive inhibitors ?

A
  • Organophosphates
  • Proton pump inhibitors
44
Q

Define the term ‘End-product inhibitor’ ?

A

End-product Inhibitor - Enzyme inhibition that occurs when the product of a reaction acts as an inhibitor to the enzyme that produces it

45
Q

What is the role of ‘end-product inhibitors’ ?

A
  • They serve as negative feedback/ a control mechanism so excess products aren’t made and resources aren’t wasted
  • Non-competitive reversible inhibition
46
Q

Define the term ‘cofactors’ ?

A

Cofactors - An additional non-protein component necessary for the effective functioning of an enzyme as a biological catalyst

47
Q

What are the different types of cofactors ?

A
  • Cofactors ( Inorganic cofactors )
  • Coenzymes ( Organic cofactors )
  • Prosthetic groups ( Tightly bounds cofactors/ required by enzymes to carry out catalytic function )
48
Q

Where are inorganic cofactors obtained from ?

A

They are obtained via the diet as minerals

49
Q

Name an example of inorganic cofactors ?

A

Cl- ion in enzyme amylase - Enzyme amylase ( which catalyses the breakdown of starch ) contains a Cl- ion ( its inorganic cofactor ) that is necessary for formation of amylases correctly shaped active site

50
Q

Where are organic cofactors/ coenzymes obtained from ?

A

They are obtained from vitamins in diet

51
Q

Name examples of prosthetic groups ?

A
  • Fe2+ ions / ham groups in globular protein haemoglobin
  • Zn2+ ion in carbonic anhydrase, it forms an important part of the enzymes structure necessary for the metabolism of COv2