factors affecting enzyme concentration. 2 of 34© boardworks ltd 2008 enzymes: true or false?
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Factors affecting enzyme concentration
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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.
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....
• Plot a graph
Independent variable
Rat
e of
rea
ctio
n
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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 investigatedEg 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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TemperatureEffect
Explanation
Measuring Activity
Enzyme ConcentrationEffect
Explanation
Measuring Activity
pHEffect
Explanation
Measuring Activity
Substrate ConcentrationEffect
Explanation
Measuring Activity
Explaining and measuring enzyme 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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