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biology unit 1 > 1.4 Enzymes > Flashcards

1.4 Enzymes Flashcards

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AP® Biology flashcards
1
Q

What do enzymes do

A

Control metabolic reactions.
Combine with substrate molecules at the active site to produce a product.

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2
Q

Structure of enzymes

A

Tertiary proteins. Polypeptide chain folded back on itself into a spherical, 3D globular shape

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3
Q

What bonds maintain the tertiary shape of enzymes

A

Hydrogen, ionic, disulphide and hydrophobic

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4
Q

How do bonds form in a tertiary structure/in enzymes

A

Form due to interactions between R-groups of the amino acids in the polypeptide

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5
Q

What are enzymes

A

Biological catalysts which speed up the rate of metabolic reactions

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6
Q

What does it mean that enzymes are specific

A

Each enzyme combines with a specific substrate molecule. Active site is complimentary to the substrate it binds to.

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7
Q

How do enzymes work

A

Substrate molecule fits into and binds to an active site within the enzyme to form an enzyme-substrate complex.

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8
Q

What is the lock and key hypothesis

A

Suggests that there’s an exact fit between the substrate and the active site of the enzyme.

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9
Q

What is a lysozyme

A

An enzyme found in tears and other secretions

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10
Q

Function of a lysozyme

A

To destroy pathogenic bacteria by breaking down their cell walls

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11
Q

What is the bacterial cell wall

A

A polysaccharide consisting of chains of amino sugars

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12
Q

How does the lysozyme destroy the cell wall

A

By breaking glycosidic bonds between amino sugars

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13
Q

Why is there a groove on one side of a lysozyme molecule

A

A section of polysaccharide fits into the groove

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14
Q

What bonds hold lysozyme structure in place

A

Hydrogen and ionic bonds

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15
Q

Highest level of protein structure in a lysozyme molecule?

A

Tertiary

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16
Q

Describe the lock and key hypothesis

A
  1. A substrate molecule binds to active site of enzyme molecule
  2. Enzyme substrate complex formed
  3. 2 product molecules are formed - the substrate is broke in two
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17
Q

What is the induced fit hypothesis

A

The idea that the active site changes shape ti fit the substrate molecule perfectly

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18
Q

What does the fact that a substrate can mould an enzyme’s active site to its own shape show?

A

That several different substrates can interact with the same enzyme.
This explains the broad specificity of some enzymes

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19
Q

What are anabolic reactions

A

Reactions where small molecules of substate are built up into larger molecules - BUILD bonds

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20
Q

What are catabolic reactions

A

Reactions where large molecules are broken into smaller molecules. BREAK bonds

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21
Q

Properties of enzymes

A

-Specific (each enzyme will catalyse only one particular reaction)

-High turnover number (can convert many molecules of substrate into product, quick and efficiently).

-lower activation energy (minimum energy needed to start a chemical reaction).

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22
Q

What is activation energy

A

The minimum energy needed to start a chemical reaction / the energy needed to break existing chemical bonds within molecules.

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23
Q

What do enzymes do to activation energy of a reaction

A

Lower the activation energy of a reaction. Which reduces the amount of energy needed to allow reactions to happen. E.g allows lower temps to work.

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24
Q

Factors affecting the rate of enzyme action

A

-temperature
-pH
-substrate concentration
-enzyme concentration

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25
Q

Explain the effect of temperature of rate of enzyme reaction

A

Increase in temp gives molecules greater kinetic energy.
Enzyme and substrate molecules move around more quickly, increasing the chance of more successful enzyme-substrate complexes.
Continues until optimum

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26
Q

Describe enzyme activity at 25°C

A

Low temp = low kinetic energy.
Enzyme and substrate move slowly so collide less often. Fewer complexes formed.
Product produced slowly and enzyme activity low

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27
Q

Describe enzyme activity at 37°C

A

Higher temp = greater kinetic energy.
Enzyme and substrate molecules move faster so collide more often. More successful enzyme substrate complexes formed.
Product produced quickly and enzymes activity is high

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28
Q

Describe enzyme activity at 60°C

A

Very high temps = kinetic energy too high.
Vibrations cause active site of enzyme to denature. More frequent collisions but successful complexes can’t form.
Enzyme activity decreased and less product formed

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29
Q

What happens beyond the optimum temperature in enzymes

A

Increasing kinetic energy causes vibrations which break hydrogen bonds in active site and shape of active site can no longer be maintained.
Substrate molecules can’t fit in active site so no successful enzyme substrate complexes can form since they aren’t complimentary.

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30
Q

What happens to enzymes at very low temperatures

A

Enzymes are inactivated, as molecules have little/no kinetic energy. No successful collisions so no enzyme substrate complexes form, so no product forms.

31
Q

What happens if temperature increases after inactivation

A

The enzymes activate again because of increased kinetic energy

32
Q

What does small changes in pH do to enzymes

A

Affect the rate of reaction without affecting the enzyme’s tertiary strcuture

33
Q

What does small pH changes outside the optimum range cause

A

Can cause reversible changes in enzyme structure, which results in inactivation.

34
Q

What does extreme pH do to an enzyme

A

Denatures the enzyme. The hydrogen bonding is effected so tertiary 3D structure is altered and active site changes shape

35
Q

How is an enzyme-substrate complex formed

A

The charges on the amino acid R-groups within the active site attract charges on the substrate molecule

36
Q

What are the charges of R-groups in the enzymes active site affected by

A

Affected by free H+ (hydrogen) and OH- (hydroxyl) ions. E.g. if there are too many H+ ions the active site and substrate may end up with the same charge and repel each other

37
Q

What do buffers do

A

Maintain a constant pH - adding small amounts of acid or alkali won’t alter the pH then.
Used in enzyme experiments which need constant pH

38
Q

If the enzyme concentration remains constant, what will happen to rate of reaction

A

Increases, as the substrate concentration increases, as there will be more successful collisions

39
Q

What will happen to rate of reaction at higher substrate concentration

A

Reaction will level off once all the active sites are occupied with substrate molecules. The number of available active sites become a limiting factor

40
Q

What will increasing enzyme concentration do to rate of reaction

A

Increase the rate of reaction

41
Q

Explains a substrate concentration against rate of reaction graph

A
  1. If enzyme concentration remains constant, the rate of reaction will increase as substrate concentration increases.
    Substrate concentration is a limiting factor here.
  2. The reaction will level off once all active sites are working to full capacity. Substrate concentration isn’t a limiting factor
42
Q

What is inhibition

A

Happens when enzyme action is slowed down or stopped by another substance

43
Q

How do enzyme inhibitors work

A

Inhibitor combines with the enzyme and stops it from forming an enzyme-substrate complex

44
Q

What are competitive inhibitors

A

Compete with substrate for active site.
They’re structurally similar to substrate molecule & complimentary to enzymes active site

45
Q

How do competitive inhibitors work

A

Fit in the active site instead of substrate molecules and prevents enzyme-substrate complexes forming

46
Q

What will happen to competitive inhibitors if substrate concentration increases

A

It will reduce the effect of this type of inhibitor. Because more substrates = more chance of successful collisions between enzyme and substrates so fewer active sites available to the inhibitor

47
Q

What does it mean that inhibition is reversible

A

Competitive inhibitors can bund and unbind with the active site

48
Q

How do non competitive inhibitors work

A
  1. Don’t bind to active site since they’re not complimentary. Bind to any other part of enzyme (allosteric sites).
  2. Inhibitor changes tertiary structure of enzyme, including active site.
  3. Substrates can no longer fit
49
Q

What are the sites where non competitive inhibitors bind to enzymes called?

A

Allosteric sites

50
Q

What will happen to effect of non competitive inhibitors if more substrate molecules are added

A

Unaffected because they aren’t competing for active sitr

51
Q

Describe relationship between substrate concentration and the effect of competitive inhibitors on the enzyme

A

As the substrate concentration increases, the effect on the enzyme decreases. But it still reaches maximum rate because it doesn’t stop, just slows

52
Q

Describe relationship between substrate concentration and the effect of non competitive inhibitors on the enzyme

A

After a point, no matter the increase in substrate concentration, it has no effect on the rate of reaction

53
Q

Industrial use of enzymes

A

Enzymes are used on a wide commercial scale in the food, pharmaceutical and agrochemical industries

54
Q

What are immobilised enzymes

A

Enzymes which are fixed, bond, or trapped on an inert matrix
E.g sodium alginate beads

55
Q

Explain sodium alginate beads

A
  • the beads, containing enzymes, can be packed into glass columns.
  • substrate added to top of column.
  • substrate molecules diffuse into the alginate beads and form enzyme substrate complexes with the enzymes within the bead and on the outer surface of the bead
56
Q

How can the lactose content of milk be reduced

A

By using the enzyme lactase. These will hydrolyse the disaccharide lactose into its component monosaccharides (glucose and galactose)

57
Q

Steps if immobilising the enzyme lactase in alginate beads

A
  1. Prepare sodium alginate beads, containing enzyme lactase.
  2. Run the milk through the column and test for glucose with test strip.
58
Q

Advantages of immobilised enzymes

A
  • enzyme doesn’t contaminate product.
  • can be recovered and reused.
  • only small quantity needed
  • greater control over process
  • greater stability so can denature at higher temperatures than usual
59
Q

What is pectin

A

A structural polysaccharide found in the cell walls of plant cells and in the middle lamella between cells, where it helps bind cells together

60
Q

What are pectinases

A

Enzymes that are used in industry to increase volume and clarity of fruit juice from apples

61
Q

How do you use pectinate to produce apple juice

A
  • pectinase enzyme immobilised onto the surface of a gel membrane which us placed inside a column
  • apple pulp is added to the top, and the juice id collected at the bottom
62
Q

Disadvantages of immobilised enzymes

A
  • enzymes can’t move so there’s a decreased chance of successful enzyme-substrate complexes forming.
    -time is needed to allow the substrate to diffuse through the inert gel matrix to reach the immobilised enzyme
63
Q

What do biosensors do

A

Use immobilised enzymes to detect biologically important molecules

64
Q

Advantages of biosensord

A
  • rapid
  • accurate
  • detect even low concentrations of molecules
65
Q

What do biosensors detect

A

Metabolites like glucose in a blood sample.
Can detect changes in substrate or product concentration.
Determine blood glucose levels in diabetics

66
Q

How do biosensors detect metabolites in blood

A

Converting a chemical signal into an electrical signal. Enzymes are specific so they can detect one type of molecule from a mixture

67
Q

How are biosensors used to determine blood glucose levels in diabetics

A
  1. The enzyme (glucose oxidase) is immobilised within a specialised membrane.
  2. Chemical change occurs as substrate is converted into a product.
  3. Transducer concerts this chemical change into an electrical signal.
  4. Strength of electrical signal measured by a meter
68
Q

If glucose is present in a blood sample, how does the biosensor detect it?

A
  1. Glucose diffuses through the biosensor’s semi permeable membrane.
  2. Enzyme substrate complex formed between glucose and immobilised glucose oxidase
  3. Product produces a chemical change that’s detected and turned into an electrical signal by the transducer.
  4. Signal amplified and displayed on monitor
69
Q

Relationship between product produced and substrate concentration in detecting blood glucose

A

The concentration of product produced is directly proportional to the substrate concentration.

70
Q

Do biosensors test for diabetes

A

No. They detect blood glucose levels, don’t detect diabetes

71
Q

What can immobilised urease enzymes be used for

A

Can be used to detect urea concentrations in blood and urine samples

72
Q

How do immobilised urease enzymes work to detect urea molecules

A
  1. Partially permeable membrane allows diffusion of small urea molecules into biosensor but prevents entry of larger solutes.
  2. Urea acted upon by immobilised urease and enzyme substrate complexes form.
  3. Ammonium ions are formed as a product.
  4. Transducer turns chemical signal (NH4+ ions) inti an electrical signal.
  5. Signal amplified and shown as a reading on the display
73
Q

Relationship between ammonium ions product concentration and substrate concentration

A

Product concentration is directly proportional to substrate concentration

biology unit 1 (5 decks)

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