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biology > C4 - Enzymes > Flashcards

C4 - Enzymes Flashcards

1
Q

What is anabolism?

A

Reactions of the metabolism that construct molecules from smaller units, require hydrolysis of ATP

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2
Q

What are enzymes?

A

Biological catalysts that interact substrate molecules to facilitate chemical reactions
Globular proteins

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3
Q

What is catabolism?

A

Reactions of the metabolism that break molecules down into smaller units, release energy

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4
Q

What is metabolism?

A

All the reactions and reaction pathways happening in an organism

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5
Q

What factors affect chemical reactions?

A

Temperature
pH
Pressure

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6
Q

What is Vmax

A

Maximum initial velocity or rate of an enzyme catalysed reaction

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7
Q

What needs to happen in order for a collision to be successful?

A

Molecules need to collide in the right orientation
(activation e?)

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8
Q

What do high temperatures and pressures do to the rate of reaction?

A

Increase collisions so increase rate of reaction

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9
Q

What is meant by the ‘specificity’ of an enzyme’?

A

Each enzyme catalyses one biochemical reaction

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10
Q

What is activation energy?

A

Energy required to initiate a reaction

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11
Q

What are the 2 hypotheses for how enzymes reduce the activation energy required for a biochemical reaction?

A

Lock and key hypothesis
Induced-fit hypothesis

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12
Q

What is an active site?

A

Area of an enzyme with a shape complimentary to a specific substrate, allowing enzyme to bind with specifity

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13
Q

What is a substrate

A

Substance used/acted on by another process/substance

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14
Q

Explain the lock and key hypothesis

A

-Area within tertiary structure of the enzyme has a shape complimentary to the shape of a specific substrate molecule (active site)
-Only specific substrate will bind to the active site of an enzyme
-When substrate is bound to active site, enzyme-substrate complex is formed
-Substrates react to from product in enzyme-substrate complex
-Products are released leaving enzyme unchanged

Substrate held so correct atom-groups are close enough to react
R groups in active site of enzyme form temporary bonds with substrate, which put strain on substrate molecule

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15
Q

What is an enzyme substrate complex?

A

Complex formed when a substrate is bound to the active site of an enzyme

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16
Q

Explain the induced fit hypothesis

A

Suggest active site of enzyme changes shape when substrate enters
-Initial interaction between enzyme and substrate is relatively weak
-Weak interactions rapidly induce change in enzyme’s tertiary structure, that strengthen binding, putting strain on substrate molecule
-Can weaken bond in substrate, lowering activation energy

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17
Q

What are intracellular enzymes?

A

Enzymes that work within cells

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18
Q

Give an example of an intracellular enzyme and its function

A

Catalase
Breaks down toxic hydrogen peroxide into oxygen and water quickly

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19
Q

What are extracellular enzymes?

A

Enzymes that work outside of the cell that made them

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20
Q

How do single-celled organisms use extracellular enzymes?

A

Release enzymes into their immediate environment to break down large molecules which are then absorbed by cells

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21
Q

What roles do enzymes play in the digestion of starch

A

1) Starch polymers broken down into maltose by amylase (mouth and small intestine)
2) Maltose broken down into glucose by maltase (small intestine)
Glucose is small enough to be absorbed by cells and into bloodstream

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22
Q

What role do enzymes play in the digestion of proteins?

A

Protease called trypsin catalyses digestion of proteins into peptides (small intestine)
Peptides broken down into amino acids by other proteases
Amino acids can be absorbed

23
Q

How does increasing temperature affect rate of reaction

A

Increases KE of particles
Collide more frequently
More frequent successful collisions

24
Q

What happens to the rate of reaction if temperatures surpass optimum temperature?

A

Higher temperature
Bonds vibrate more
Bonds break
Tertiary structure changes shape
Denatured and active site changed so loses its function

24
Q

What is the temperature coefficient of a reaction?

A

Q10 (2?)
Measure of how much the rate of reaction increases with a 10C temperature increase

25
Q

What is denaturation

A

Change in tertiary structure of a protein or enzyme, resulting in a loss of normal function

26
Q

What is optimum temperature

A

Temperature at which enzyme ahs highest rate of activity
(humans-40C)

27
Q

When does Q10 stop applying?

A

When optimum temperature is surpassed as enzymes are denatured

28
Q

How are enzymes adapted for extreme cold environments?

A

More flexible structures and active site
Less table
Small temperature changes will denature them

29
Q

What are thermophiles?

A

Organisms adapted to living in very hot environments

30
Q

How are enzymes adapted for extreme hot environments?

A

More stable due to increased number of bonds (hydrogen bonds and sulfur bridges)
More resistant to change as temperature rises

31
Q

Are more hydrogen ions present in acidic environments or alkaline environments?

A

low pH acidic environments

32
Q

How does pH affect enzymes?

A

-Active site will only be the right shape at a specific hydrogen ion concentration (optimum pH)
-When pH changes, structure of active site is altered (but can be reversed)

32
Q

What happens if the pH changes more significantly?

A

Structure of enzyme altered permanently and it denatures

33
Q

Explain how H+ ions affect enzymes

A

More H+ ions present (low pH), the less R-groups are able to interact with each other
Causes bonds to break and the shape of the enzyme to change
+Reverse

34
Q

What happens to the rate of reaction when you increase substrate concentration?

A

Number of substrate molecules per volume increase
Higher collision rate with active site of enzymes
Formation on complex increases
Rate of reaction increases up to Vmax (saturated)

35
Q

What happens to the rate of reaction when you increase enzyme concentration?

A

Number of enzyme molecules per volume increase
Higher active site available for collision
Formation on complex increases
Rate of reaction increases up to Vmax (saturated)

36
Q

What is a cofactor?

A

Non protein component necessary for the effective functioning of an enzyme

37
Q

What is an inhibitor?

A

Factor that prevents/reduces the rate of an enzyme catalysed reaction

37
Q

How does competitive inhibition work?

A

-Molecule/part of molecule that has a similar shape to the substrate of an enzyme can fit into the active site
-This blocks substrate from entering active site, preventing enzyme from catalysing reaction
-Enzyme cannot carry out its function so is inhibited
-Non-substrate molecule is an inhibitor and competes with substrate molecule to bind with active site of enzyme

38
Q

How does non-competitive inhibition work?

A

-Inhibitor binds to enzyme at a location other than the active site (allosteric site)
-Binding causes enzyme’s tertiary structure and active site to change
-Results in active site no longer having complimentary shape to substrate
-Enzyme cannot carry out its function and is inhibited

39
Q

What is the effect on competitive inhibition on the rate of reaction?

A

Reduces rate of reaction for a given concentration of a substrate
Doesn’t change Vmax
If substrate concentration increased enough, original Vmax can still be reached

39
Q

Give an example of competitive inhibition?

A

Statins - enzyme used in synthesis of cholesterol
Aspirin - COX enzymes used in synthesis of prostaglandins and thromboxane, chemicals inducing pain and fever (irreversible)

40
Q

What is the effect on non-competitive inhibition on the rate of reaction?

A

Increasing concentration of enzyme or substrate has no effect
Increasing concentration of of inhibitor, reduces rate of reaction further

41
Q

Give an example of irreversible non-competitive inhibition?

A

Proton pump inhibitors irreversibly block an enzyme responsible for secreting H+ ions into stomach

42
Q

What is end-product inhibition?

A

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

43
Q

What is a negative feedback control mechanism for enzyme catalysed reactions?

A

End-product inhibition

44
Q

Explain the role of enzyme inhibitors in respiration?

A

Respiration is a metabolic pathway resulting in the production of ATP
1) Two phosphate groups added to glucose
2) Addition of second phosphate is catalysed by enzyme PFK, results in initial breakdown of glucose
3) This enzyme is competitively inhibited by ATP
-When levels of ATP are high, more ATP binds to allosteric site on PFK
-When ATP is used up, less binds to PFK

45
Q

What is a coenzyme?

A

An enzyme which has a cofactor that is an organic molecule

46
Q

What is a prosthetic group?

A

Cofactors that are required by enzymes to carry out their catalytic function
Tightly bound and form a permanent feature

47
Q

What is precursor activation

A

Change in shape that precursor enzymes need to undergo, particularly to the active site, to be activated

48
Q

What is the name of enzymes produced in an inactive form

A

Inactive precursor enzymes

49
Q

How are precursor enzymes activated?

A

Addition of a cofactor to apoenzyme (precursor protein before cofactor added) becomes haloenzyme

50
Q

How else can precursor enzymes be activated?

A

Another enzyme
Change in pH or temperature

Causing change in tertiary structure

biology (13 decks)

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