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Mr Stonehouse BIOLOGY > 4.0 ENZYMES > Flashcards

4.0 ENZYMES Flashcards

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
What do competitive, reversible inhibitors do?
This inhibitor competes with the normal substrate for the active site, preventing the substrate from entering and forming any product.
26
What do non-competitive, reversible inhibitors do?
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
How do competitive inhibitors affect enzyme action?
-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
How do non-competitive inhibitors affect enzyme action?
-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
What are metabolic pathways?
Sequences of chemical reactions, each controlled by a specific enzyme.
30
What is the typical sequence of chemical reaction in a metabolic pathway?
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
What is feedback Inhibition?
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
How are enzymes classified?
According to the type of chemical reaction they catalyze.
33
What are hydrolase enzymes?
Enzymes that catalyze a hydrolysis reaction.
34
What type of enzyme is Maltase and what does it catalyze?
hydrolase enzyme, catalyzes the hydrolysis reaction of maltose into two glucose molecules
35
What are Transferases?
enzymes that catalyze reactions involving the transfer of atoms/ groups of atoms from one molecule to another
36
What happens during cellular respiration?
a phosphate group is transferred from a molecule of ATP to a glucose molecule (using transferases) - activating the glucose.
37
What are oxidoreductases?
Enzymes that catalyze reactions involving oxidation and reduction.
38
What is oxidation?
-addition of oxygen -removal of hydrogen atoms -removal of electrons
39
What is reduction?
-removal of oxygen -addition of hydrogen atoms -addition of electrons
40
What do oxidoreductases play an important role in?
biochemistry of respiration
41
What are cofactors?
non-protein chemical compound / metallic ion
42
What are cofactors required for?
enzyme's activity as a catalyst - considered a 'helper molecule' that assist in biochemical transformations.
43
What are a couple of types of cofactors?
Zn++ ---> enzyme = carbonic anhydrase Fe++/Fe+++ ---> enzyme = cytochromes/haemoglobin
44
What are holoenzymes?
refers to the active enzyme with a non protein component (cofactor)
45
What are apoenzymes?
refers to an inactive enzyme without its non protein component (no cofactor)
46
What is a coenzyme?
small organic molecule that binds with a specific enzymes, helping to catalyze a reaction
47
What are the main coenzymes used in respiration?
NAD (Nicotinamide adenine denucleotide) CoA (coenzyme A) FAD (flavine adenine dinucleotide)
48
What are prosthetic groups?
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
What are some examples of prosthetic groups?
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
How do you calculate the gradient?
create a tangent -change in y / change in x
51
What are the main types of reaction?
-gas production -digestion of a solid -digestion of a liquid -colour change
52
How do you carry out a gas production experiment?
-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
How do you carry out a digestion of a solid experiment?
-calculate percentage weight change -change in diameter -volume of liquid produced
54
How do you carry out a liquid digestion experiment?
-diffusion out of a dialysis tube
55
How do you carry out a colour change experiment?
-starch reacts with iodine -peptide bonds are stained via the biuret test -reducing vs. non-reducing sugars
56
What is the catalase formula?
2H2O2 -(catalase)-> 2H20+O2
57
What is a 10 fold serial dilution?
reducing the concentration of a solution by a factor of 10 that is to one-tenth the original concentration
58
What is a 2 fold serial dilution?
reducing concentration of a solution by a factor of 2 that reduces the original concentration by a half
59
What is standard deviation?
measure of how spread data is from a mean
60
How are standard deviations measured on a graph?
-error bars -vertical line, before and after plotted point
61
What is the standard deviation formula?
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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