Factors affecting enzyme
concentration
Enzymes: true or false?
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• Spec Check
• explain the importance of cofactors and
coenzymes in enzyme-controlled reactions;
•
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What are cofactors?
Some enzymes require the addition of a non-protein
substance called a cofactor before they can catalyze a
reaction. There are two main types of cofactor:

activators – inorganic groups that are permanently bound
to the enzyme and so are a type of prosthetic group.
Common examples include iron, zinc and copper.

coenzymes – organic
molecules that bind only
temporarily to the enzyme,
transferring a chemical group
necessary required for the
reaction. Examples include
vitamin C and ATP.
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vitamin C
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• Spec Check
• describe and explain the effects of pH, temperature,
enzyme concentration and substrate concentration on
enzyme activity;
•
describe how the effects of pH, temperature, enzyme
concentration and substrate concentration on enzyme
activity can be investigated experimentally;
•
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• Enzyme Experiments
• Measuring effects on enzymes:
• Measure the amount of product made or
substrate used up.
Can be done by
Measuring the amount after a fixed period
Measuring the amount at pre-determined time
intervals
If you measure time taken for something you can
then calculate the rate of reaction by 1/time
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• Next....
Rate of reaction
• Plot a graph
Independent variable
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• Controlled factors in experiments
• Equilibration – incubating the substrate and
the enzyme before the start of the
experiment to ensure they reach the
required temperature before the experiment
begins
• Control all other factors except the one
being investigated
Eg accurate measurements, temperature, pH
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• Calculating initial rate
• This is important if you want to compare the
rate of a reaction with the rate after a factor
has been altered.
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Measuring the initial rate of reaction
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Explaining and measuring enzyme activity
Temperature
Effect
Enzyme Concentration
Effect
Explanation
Explanation
Measuring Activity
Measuring Activity
pH
Effect
Substrate Concentration
Effect
Explanation
Explanation
Measuring Activity
Measuring Activity
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Effect of temperature on enzymes
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Effect of pH on enzymes
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Rate of reaction experiment
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Effect of substrate concentration on rate
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Effect of enzyme concentration on rate
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• Now complete the rest of the table
• Use the activity sheet pack per group
• Use p142-3 in purple books
• Use p 138 in green books
• You must know a method to measure
enzyme activity for each factor
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Factors affecting rate of reaction
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• Spec Check
• (f) explain the effects of competitive and non-competitive
inhibitors on the rate of enzyme-controlled reactions, with
reference to both reversible and non-reversible inhibitors;
• (g) explain the importance of cofactors and coenzymes in
enzyme-controlled reactions;
• (h) state that metabolic poisons may be enzyme inhibitors,
and describe the action of one named poison;
• (i) state that some medicinal drugs work by inhibiting the
activity of enzymes (HSW6a).
•
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