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Mr Stonehouse BIOLOGY > 4.0 ENZYMES > Flashcards

4.0 ENZYMES Flashcards

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1
Q

What are enzymes?

A

Biological catalysts, globular proteins

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2
Q

How much do enzymes increase the rate of reaction by?

A

10 to the power of 20 compared to uncatalyzed reactions

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3
Q

What are the main characteristics of enzymes?

A

-high molecular weights
-sensitive to temperature changes
-sensitive to pH
-possess an active site

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4
Q

What is the induced fit model?

A

binding of the substrate induces the enzyme to change shape and form an exact fit

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5
Q

What does the induced fit take into account that the lock and key model did not?

A

That proteins (enzymes) have 3D flexibility

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6
Q

Why are enzymes catalysts?

A

they lower the activation energy needed to drive a reaction

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7
Q

What are the main factors that affect the rate of reaction?

A

-temperature
-pH
-substrate concentration
-enzyme concentration
-inhibitors
-activators

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8
Q

What are molecular collisions?

A

when molecules are constantly in motion and collide with each other

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9
Q

How does temperature affect molecular collisions?

A

At high temperatures, there are more enzyme-substrate complexes being made so the rate increases.

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10
Q

What is the optimum temperatures for enzymes to work in?

A

37c –> 40c
- not all, some extremophiles have higher optimums

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11
Q

What happens to enzymes when the temperature changes away from the optimum?

A

If too low, rate decreases
If too high, enzymes denature as the bonds stabilizing the active sites structure are broken - the shape changes.

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12
Q

How much does the rate of reaction increase when temperature increases?

A

reaction doubles for every 10*c rise in temperature.
This is the temperature coefficient (Q10=2).

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13
Q

What is it meant by acidity?

A

hydrogen ions (H+), low pH

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14
Q

What is meant by alkaline (basic)?

A

hydroxyl ions (OH-), high pH

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15
Q

What is the pH of water?

A

7.0 (neutral)

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16
Q

What happens to the rate when the solution gets more acidic/alkaline?

A

increases by a factor of 10 per pH change

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17
Q

What is the optimum pH for enzymes?

A

Each enzyme has its own optimum pH where the rate is the maximum.

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18
Q

What shape graphs do the effects of pH have on the rate of reaction?

A

bell shaped

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19
Q

What is the effect of substrate concentration on rate?

A

low substrate concentration = low product concentration per unit time
high substrate concentration = more product formation so increased reaction rate

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20
Q

What happens if substrate concentration is further increased?

A

maximum product formed, max rate of reaction.

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21
Q

What happens if there is excess substrate concentration?

A

no further increase in product formation - maximum rate is maintained
- enzyme concentration becomes the limiting factor

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22
Q

What happens if the enzyme concentration is increased?

A

rate is directly proportional to enzyme concentration - substrate concentration is rarely the limiting factor.

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23
Q

What does the presence of inhibitors do to the rate of reaction?

A

Decreases the rate by reversible combination with the enzyme

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24
Q

What are the four types of inhibitors?

A

Competitive, reversible
Competitive, irreversible
Non-competitive, reversible
Non-competitive, irreversible

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25
Q

What do competitive, reversible inhibitors do?

A

This inhibitor competes with the normal substrate for the active site, preventing the substrate from entering and forming any product.

26
Q

What do non-competitive, reversible inhibitors do?

A

The inhibitor molecule attaches to the enzyme at a position away from the active site - preventing the substrate from being converted into products by changing the shape of the active site (preventing induced fit).
- This has an indirect effect

27
Q

How do competitive inhibitors affect enzyme action?

A

-when substrate concentration is low, inhibitor competes successfully for the active site - reducing rate.
-when substrate concentration is high, inhibitor does not compete successfully - maximum rate is achieved.

28
Q

How do non-competitive inhibitors affect enzyme action?

A

-at low substrate concentrations, rate is reduced, substrate molecules are not converted into products
-at high substrate concentrations, all active sites are occupied but products are not made (maximum rate is never achieved)

29
Q

What are metabolic pathways?

A

Sequences of chemical reactions, each controlled by a specific enzyme.

30
Q

What is the typical sequence of chemical reaction in a metabolic pathway?

A

The initial substrate (A) is converted by a series of intermediate compounds (B,C+D) into the final product (E).
A-(enzyme1)->B-(e2)->C-(e3)->D-(e4)->E

31
Q

What is feedback Inhibition?

A

further production of the end product is prevented - the excess end product inhibits the first enzyme in the pathway to stop A turning to B.

32
Q

How are enzymes classified?

A

According to the type of chemical reaction they catalyze.

33
Q

What are hydrolase enzymes?

A

Enzymes that catalyze a hydrolysis reaction.

34
Q

What type of enzyme is Maltase and what does it catalyze?

A

hydrolase enzyme, catalyzes the hydrolysis reaction of maltose into two glucose molecules

35
Q

What are Transferases?

A

enzymes that catalyze reactions involving the transfer of atoms/ groups of atoms from one molecule to another

36
Q

What happens during cellular respiration?

A

a phosphate group is transferred from a molecule of ATP to a glucose molecule (using transferases) - activating the glucose.

37
Q

What are oxidoreductases?

A

Enzymes that catalyze reactions involving oxidation and reduction.

38
Q

What is oxidation?

A

-addition of oxygen
-removal of hydrogen atoms
-removal of electrons

39
Q

What is reduction?

A

-removal of oxygen
-addition of hydrogen atoms
-addition of electrons

40
Q

What do oxidoreductases play an important role in?

A

biochemistry of respiration

41
Q

What are cofactors?

A

non-protein chemical compound / metallic ion

42
Q

What are cofactors required for?

A

enzyme’s activity as a catalyst
- considered a ‘helper molecule’ that assist in biochemical transformations.

43
Q

What are a couple of types of cofactors?

A

Zn++ —> enzyme = carbonic anhydrase
Fe++/Fe+++ —> enzyme = cytochromes/haemoglobin

44
Q

What are holoenzymes?

A

refers to the active enzyme with a non protein component (cofactor)

45
Q

What are apoenzymes?

A

refers to an inactive enzyme without its non protein component (no cofactor)

46
Q

What is a coenzyme?

A

small organic molecule that binds with a specific enzymes, helping to catalyze a reaction

47
Q

What are the main coenzymes used in respiration?

A

NAD (Nicotinamide adenine denucleotide)
CoA (coenzyme A)
FAD (flavine adenine dinucleotide)

48
Q

What are prosthetic groups?

A

Non protein group forming part of/combined with a protein (not always an enzyme)
- tightly bound, specific non polypeptide unit (not composed of amino acids) required for biological functions of some proteins

49
Q

What are some examples of prosthetic groups?

A

Haem group in haemoglobin (not an enzyme)
Zinc ion in carbonic anhydrase (enzyme)
They can be organic (e.g. vitamin, sugar, lipid) or inorganic (e.g. metal ion).

50
Q

How do you calculate the gradient?

A

create a tangent
-change in y / change in x

51
Q

What are the main types of reaction?

A

-gas production
-digestion of a solid
-digestion of a liquid
-colour change

52
Q

How do you carry out a gas production experiment?

A

-count bubble formation or
-time for an enzyme-soaked disc to rise in substrate solution or
-gas syringe
-displacement of syringe cap with increasing volume of gas
-pressure change in sealed environment (data logger)

53
Q

How do you carry out a digestion of a solid experiment?

A

-calculate percentage weight change
-change in diameter
-volume of liquid produced

54
Q

How do you carry out a liquid digestion experiment?

A

-diffusion out of a dialysis tube

55
Q

How do you carry out a colour change experiment?

A

-starch reacts with iodine
-peptide bonds are stained via the biuret test
-reducing vs. non-reducing sugars

56
Q

What is the catalase formula?

A

2H2O2 -(catalase)-> 2H20+O2

57
Q

What is a 10 fold serial dilution?

A

reducing the concentration of a solution by a factor of 10 that is to one-tenth the original concentration

58
Q

What is a 2 fold serial dilution?

A

reducing concentration of a solution by a factor of 2 that reduces the original concentration by a half

59
Q

What is standard deviation?

A

measure of how spread data is from a mean

60
Q

How are standard deviations measured on a graph?

A

-error bars
-vertical line, before and after plotted point

61
Q

What is the standard deviation formula?

A

s=..…/∑(x-¯x)2
…….\/ ¯¯n-1¯¯¯
∑=sum of
x=measured value/results from sample
¯x=mean value
n=total number of values in the sample

Mr Stonehouse BIOLOGY (15 decks)

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