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Biology Unit 1 > 1.4 Enzymes > Flashcards

1.4 Enzymes 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
Explain the effect of temperature of rate of enzyme reaction
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
26
Describe enzyme activity at 25°C
Low temp = low kinetic energy. Enzyme and substrate move slowly so collide less often. Fewer complexes formed. Product produced slowly and enzyme activity low
27
Describe enzyme activity at 37°C
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
28
Describe enzyme activity at 60°C
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
29
What happens beyond the optimum temperature in enzymes
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.
30
What happens to enzymes at very low temperatures
Enzymes are inactivated, as molecules have little/no kinetic energy. No successful collisions so no enzyme substrate complexes form, so no product forms.
31
What happens if temperature increases after inactivation
The enzymes activate again because of increased kinetic energy
32
What does small changes in pH do to enzymes
Affect the rate of reaction without affecting the enzyme’s tertiary strcuture
33
What does small pH changes outside the optimum range cause
Can cause reversible changes in enzyme structure, which results in inactivation.
34
What does extreme pH do to an enzyme
Denatures the enzyme. The hydrogen bonding is effected so tertiary 3D structure is altered and active site changes shape
35
How is an enzyme-substrate complex formed
The charges on the amino acid R-groups within the active site attract charges on the substrate molecule
36
What are the charges of R-groups in the enzymes active site affected by
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
What do buffers do
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
If the enzyme concentration remains constant, what will happen to rate of reaction
Increases, as the substrate concentration increases, as there will be more successful collisions
39
What will happen to rate of reaction at higher substrate concentration
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
What will increasing enzyme concentration do to rate of reaction
Increase the rate of reaction
41
Explains a substrate concentration against rate of reaction graph
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
What is inhibition
Happens when enzyme action is slowed down or stopped by another substance
43
How do enzyme inhibitors work
Inhibitor combines with the enzyme and stops it from forming an enzyme-substrate complex
44
What are competitive inhibitors
Compete with substrate for active site. They’re structurally similar to substrate molecule & complimentary to enzymes active site
45
How do competitive inhibitors work
Fit in the active site instead of substrate molecules and prevents enzyme-substrate complexes forming
46
What will happen to competitive inhibitors if substrate concentration increases
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
What does it mean that inhibition is reversible
Competitive inhibitors can bund and unbind with the active site
48
How do non competitive inhibitors work
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
What are the sites where non competitive inhibitors bind to enzymes called?
Allosteric sites
50
What will happen to effect of non competitive inhibitors if more substrate molecules are added
Unaffected because they aren’t competing for active sitr
51
Describe relationship between substrate concentration and the effect of competitive inhibitors on the enzyme
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
Describe relationship between substrate concentration and the effect of non competitive inhibitors on the enzyme
After a point, no matter the increase in substrate concentration, it has no effect on the rate of reaction
53
Industrial use of enzymes
Enzymes are used on a wide commercial scale in the food, pharmaceutical and agrochemical industries
54
What are immobilised enzymes
Enzymes which are fixed, bond, or trapped on an inert matrix E.g sodium alginate beads
55
Explain sodium alginate beads
- 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
How can the lactose content of milk be reduced
By using the enzyme lactase. These will hydrolyse the disaccharide lactose into its component monosaccharides (glucose and galactose)
57
Steps if immobilising the enzyme lactase in alginate beads
1. Prepare sodium alginate beads, containing enzyme lactase. 2. Run the milk through the column and test for glucose with test strip.
58
Advantages of immobilised enzymes
- 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
What is pectin
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
What are pectinases
Enzymes that are used in industry to increase volume and clarity of fruit juice from apples
61
How do you use pectinate to produce apple juice
- 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
Disadvantages of immobilised enzymes
- 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
What do biosensors do
Use immobilised enzymes to detect biologically important molecules
64
Advantages of biosensord
- rapid - accurate - detect even low concentrations of molecules
65
What do biosensors detect
Metabolites like glucose in a blood sample. Can detect changes in substrate or product concentration. Determine blood glucose levels in diabetics
66
How do biosensors detect metabolites in blood
Converting a chemical signal into an electrical signal. Enzymes are specific so they can detect one type of molecule from a mixture
67
How are biosensors used to determine blood glucose levels in diabetics
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
If glucose is present in a blood sample, how does the biosensor detect it?
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
Relationship between product produced and substrate concentration in detecting blood glucose
The concentration of product produced is directly proportional to the substrate concentration.
70
Do biosensors test for diabetes
No. They detect blood glucose levels, don’t detect diabetes
71
What can immobilised urease enzymes be used for
Can be used to detect urea concentrations in blood and urine samples
72
How do immobilised urease enzymes work to detect urea molecules
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
Relationship between ammonium ions product concentration and substrate concentration
Product concentration is directly proportional to substrate concentration

Biology Unit 1 (6 decks)

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