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Biology AS1 Knowledge Organiser > Enzymes > Flashcards

Enzymes Flashcards

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1
Q

What is an enzyme?

A

An enzyme is a biological catalyst that speeds up metabolic reactions

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2
Q

What type of protein is an enzyme?

A

Globular proteins

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3
Q

What do enzymes do?

A

Enzymes lower the activation energy of a reaction to speed up the rate of reaction

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4
Q

What does an enzyme and a substrate form?

A

The substrate interacts with the complimentary active site to form the enzyme-substrate complex.
The reaction changes the substrate to an enzyme-product complex and will no longer fit the active site and are then released. The enzyme will remain unchanged

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5
Q

What is catabolism?

A

The breakdown of molecules

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6
Q

What is anabolism?

A

The building up of molecules

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7
Q

What is the term used to describe the fact that each enzyme is specific to a particular substrate?

A

Enzyme specificity

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8
Q

What is the Lock and Key model?

A

The Lock and Key model proposes that the enzyme active site is an exact match to the substrate shape. (complimentary shapes)

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9
Q

What is the Induced Fit model?

A

The Induced Fit model proposes that the active site of the enzyme very closely matches the shape of the substrate.

The active site can mould itself around the substrate, making the enzyme more flexible.

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10
Q

What is a cofactor?

A

Cofactors are non-protein substances that form attachments to enzymes. Some enzymes require cofactors in order to function

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11
Q

Give examples of cofactors

A

Metal ions such as Mg2+, Ca2+ and Fe3+

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12
Q

What does a cofactor do?

A

A cofactor will attach to the enzyme and change the shape of the active site, enabling reaction to take place

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13
Q

What enzyme requires the prosthetic group haem?

A

The enzyme catalase

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14
Q

What is a coenzyme?

A

Coenzymes are particular types of cofactors. They are non-protein, organic molecules necessary for enzyme action.

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15
Q

What are the properties of enzymes?

A

Highly substrate specific, globular proteins, soluble, spherical, tertiary structure

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16
Q

What affects enzyme activity?

A

Concentration, Temperature and pH

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17
Q

How does concentration affect enzyme activity?

A

If the number of enzymes is a fixed rate and the level of substrate is increased, enzyme activity will also increase for a period of time. The limiting number of enzyme active sites will level off the rate of reaction.

On a graph:
Increase then becomes level

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18
Q

How does temperature affect enzyme activity?

A

Increasing temperature increases kinetic energy of the enzyme and substrate molecules. This increases the possibility of successful collisions between enzymes and substrates leading to the formation of enzyme-substrate complexes.

The rate of reaction until the reaction reaches the optimum temperature.

After the optimum temperature the high kinetic energy begins to break the weak hydrogen bonds within the enzyme, changing the shape of the active site. If too many bonds are broken the enzymes ceases to function and is therefore denatured

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19
Q

What is the optimum temperature for enzymes in mammals?

A

Around 40°C

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20
Q

How does pH affect enzyme activity?

A

Each enzyme also has an optimum pH. Changes in pH causes reduced enzyme activity as the bonds are disrupted

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21
Q

What bonds does temperature especially disrupt?

A

Hydrogen bonds

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22
Q

What bonds does pH especially disrupt?

A

Ionic Bonds

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23
Q

What is an enzyme inhibitor?

A

Enzyme inhibitors are substances that interfere with enzyme action. They reduce the activity by either directly or indirectly affecting the function of the active sitr

24
Q

What is competitive inhibition?

A

The inhibitor substance competes with the usual substrate for the active site.

25
Q

How does a competitive inhibitor do it’s job?

A

Competitive inhibits are very similar in shape to the usual substrate. The inhibitor will attach itself to part of the active site, restricting usual enzyme-substrate complexes formation.

26
Q

What is non-competitive inhibition?

A

The inhibitor attaches itself to a part of the enzyme other than the active site.
The inhibitor changes the shape of the active site so that it is no longer complimentary to the substate molecule.

27
Q

How can changing substrate concentration help distinguish between competitive and non-competitive inhibition?

A

If the substrate concentration is increased it can overcome the effect of competitive inhibition but will not reduce the effect of non-competitive inhibition

28
Q

Is inhibition a temporary effect?

A

Many inhibitions are reversible, though some are irreversible causing permanent damage to the enzymes structure, and function.

29
Q

What is an allosteric enzyme?

A

An enzyme with a second site where non-substrate molecules can attach

30
Q

Give an example of a non-reversible inhibitor.

A

Cyanide is a non-reversible inhibitor of the respiratory enzyme Cytochrome Oxidiase

31
Q

Describe how an enzyme inhibitor can be used as a therapeutic drug

A

Enzyme inhibitors can be used to reduce or stop the progression of disease by targeting disease causing enzymes

32
Q

What characteristics must enzyme inhibitors have to work as therapeutic drugs?

A

Specific to the enzyme in the disease progression
Work well at low dosage to prevent toxic build up of inhibitor

33
Q

Explain how penicillin works as a therapeutic drug.

A

Penicillin inhibits the enzyme responsible for the formation of cross-links in bacterial cell walls

34
Q

Explain how some antiviral drugs work as a therapeutic drug

A

By inhibiting the DNA/RNA polymerase essential for viral replication

35
Q

Explain how Angiotensin Converting Enzyme (ACE) inhibitors can be used as a therapeutic drug.

A

ACE inhibitors prevent vasoconstriction of coronary arteries, helping to lower blood pressure

36
Q

Describe how an enzyme can be used as a biomarker of disease

A

The presence of certain enzymes can be used as a diagnostic tool to confirm that a particular disease is present. By monitoring the levels of these enzymes overtime, disease progression can be monitored

37
Q

How can enzymes be monitored?

A

By testing the blood, urine or sputum

38
Q

What is sputum?

A

The thick liquid that is coughed up from the respiratory tract (also known as phlegm)

39
Q

Give an example of an enzyme that is used as a biomarker of disease and explain how it is used as a biomarker.

A

Elastase is a biomarker for lung disease. It is released by white blood cells. Elastase breaks down bacterial pathogens and is part of the immune response.

Elastase also breaks down elastin, which continuities to the elasticity of the alveoli.

40
Q

How is elastase activity stopped after infection?

A

The enzyme inhibitor, alpha-1-anyitrysin (A1AT) prevents elastase activity after the infection has been cleared.

41
Q

How is elastase-induced emphysema caused?

A

Cigarette smoke causes an increase in elastase production and there is a limited amount of A1AT present to control the elastase. This causes the elastin in the alveoli to be broken down

42
Q

What are immobilised enzymes?

A

Immobilised enzymes are trapped within, or attached to, appropriate inorganic or organic materials to maximise efficiency of the enzymes

43
Q

Describe the method of Adsorption

A

The enzymes are attached by weak forced to an inert substance such as glass or a matrix

44
Q

Describe the method of Entrapment

A

The enzymes are trapped within polymers such as alginate beads or microspheres

45
Q

Describe the method of Encapsulation

A

The enzymes are trapped inside a selectively permeable membrane such as nylon

46
Q

Describe the method of Cross-Linkage

A

The enzymes are covalently bonded to a matrix such as cellulose as a consequence of chemical reactions

47
Q

State 5 advantages of enzyme immobilisation

A
  • Enzymes are more resistant to changes in pH
  • Enzymes are more thermostable
  • Commercial processes can be continuous (faster and less waste produced)
  • Enzymes can be retained and reused
  • End product is not contaminated by the enzymes used (simplifies down-streaming process and refuses purification costs)
48
Q

State and explain 4 disadvantages of enzyme immobilisation

A
  • Enzyme active sits may be incorrectly orientated as part of the active site is attached to the glass (adsorption) or surrounded by polymers (entrapment)
  • Enzymes may be washed away as weak forces are what attaches them to the glass (adsorption)
  • Reduced speed of diffusion as substrate has to move through membrane or matrix (enmeshment + cross-linkage)
49
Q

What is a biosensor?

A

A device which uses a living organism or biological molecule (especially enzymes or antibodies) to detect the presence of chemicals

50
Q

Describe how immobilised enzymes can be used in diagnostic reagent strips as a biosensor

A

The molecule being monitored will react with immobilised enzymes and the reaction produced causes a colour change it is converted into an electrical signal

51
Q

Give examples of immobilised enzymes being used as diagnostic strips as biosensors

A

Clinistix: when glucose is present the enzyme is activated to produce a colour change

Pregnancy tests: pregnancy hormones attach to the antibody in test strips, this activated the enzyme to produce a colour change

52
Q

Why are enzymes very effective as biosensors?

A

Enzymes are very specific and can be used to identify individual molecules.
They are also quantative

53
Q

Describe how an enzyme inhibitor can be used as a diagnostic reagent strip

A

Inhibitors can detect the presence of an enzyme. The enzyme will bind by its active site to the inhibitor that’s attached to the diagnostic strip.

54
Q

Why use an inhibitor rather than the normal substrate?

A

Enzyme inhibitors are more specific than substrates

55
Q

Give examples of enzyme inhibitors being used in diagnostic strips

A

Early identification of cardiovascular disorders (pre-eclampsia) are done by the detection of specific enzymes present in samples

Biology AS1 Knowledge Organiser (3 decks)

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