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Questions and Answers
What are the four factors that affect enzyme activity?
Temperature, pH, enzyme concentration, substrate concentration.
What happens when the temperature is increased?
The rate of an enzyme-controlled reaction increases.
What does more heat mean for the molecules in an enzyme-controlled reaction?
More kinetic energy, so the molecules move faster.
If the molecules move faster, what is more likely to happen?
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What also increases as a result of more heat?
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If the energy of the collisions increases, what are the collisions more likely to result in?
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What happens if the temperature gets too high?
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Explain why if the temperature gets too high the reaction stops.
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What does the enzyme become if the active site changes shape and the enzyme and substrate no longer fit?
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What does the enzyme no longer function as if it becomes denatured?
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What does every enzyme have?
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What is the optimum temperature of most human enzymes?
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What is the optimum temperature for some enzymes, such as those used in biological washing powders?
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What shows how the rate of reaction changes with temperature?
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What does the temperature coefficient value show?
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At temperatures before the optimum, what does a Q10 value of 2 mean?
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What does a Q10 value of 3 mean?
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What is the Q10 value of most enzyme-controlled reactions?
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What does pH affect?
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What do all enzymes have?
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What pH do most human enzymes work best at?
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What pH does pepsin work best at?
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What bonds hold the enzyme's tertiary structure in place?
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What happens above and below the optimum pH?
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What happens to the enzyme's active site if the ionic and hydrogen bonds are affected?
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What does the enzyme become if the active site changes shape?
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What does enzyme concentration affect?
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What is more likely to happen if there are more enzyme molecules in a solution?
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Therefore, what does increasing the concentration of the enzyme increase also?
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What happens if the amount of substrate is limited and you keep adding more enzyme molecules?
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What does substrate concentration affect?
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What happens if the substrate concentration is increased?
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Why does the rate of reaction increase if the substrate concentration is higher?
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When does the rate of reaction stop increasing?
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Why does the rate of reaction stop increasing after the saturation point is reached?
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What happens to substrate concentration over time during a reaction?
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If the substrate concentration decreases over time and no other variables are changed in the reaction, what will happen to the rate of reaction?
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What is the highest rate of reaction during the reaction?
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Name two ways you can measure the rate of an enzyme-controlled reaction.
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What enzyme would you use to measure how fast a product appears?
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Why would catalase be a good example?
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How would you measure the appearance of a product using catalase?
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What enzyme would you use to measure the disappearance of the substrate?
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What solution would you use to detect starch?
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How would you time how long it takes for the starch to disappear?
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Why would you alter the conditions of the reaction?
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Describe how you would use amylase to measure the disappearance of a substrate.
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Study Notes
Factors Affecting Enzyme Activity
- Four main factors influencing enzyme activity: temperature, pH, enzyme concentration, and substrate concentration.
Temperature Effects
- Increased temperature raises the rate of enzyme-controlled reactions.
- Higher temperatures provide more kinetic energy, causing molecules to move faster.
- Faster-moving molecules lead to a higher likelihood of collisions between enzymes and substrates.
- Increased kinetic energy also boosts the energy of collisions, making reactions more probable.
- If temperatures exceed a certain threshold, enzyme activity halts; excessive heat denatures enzymes.
- High temperatures cause vibrations in enzyme molecules, breaking bonds that maintain their shape, altering the active site.
- An altered active site renders the substrate unable to bind, resulting in a denatured enzyme.
Optimum Temperature
- Every enzyme has an optimum temperature; for most human enzymes, this is approximately 37 degrees Celsius.
- Some enzymes, like those in biological washing powders, may have an optimum temperature of around 60 degrees Celsius.
Temperature Coefficient (Q10)
- Q10 indicates how much the reaction rate changes with a 10-degree Celsius increase.
- A Q10 value of 2 means the rate doubles; a value of 3 signifies a tripling in reaction rate.
pH Effects
- pH significantly affects enzyme activity as each enzyme has an optimum pH level.
- Most human enzymes function best at pH 7, though there are exceptions.
- Pepsin, an enzyme in the stomach, operates optimally at a highly acidic pH of 2.
- Ionic and hydrogen bonds maintain the enzyme's tertiary structure; deviations in pH can disrupt these bonds.
- Changes in pH can deform the active site, leading to enzyme denaturation.
Enzyme Concentration
- Enzyme concentration directly impacts reaction rates. More enzyme molecules heighten Collision likelihood with substrate, increasing reaction rates.
- If substrate availability is limited, adding excess enzymes eventually yields no additional effect, as all active sites may be occupied.
Substrate Concentration
- Higher substrate concentrations generally lead to increased reaction rates until reaching a saturation point.
- Once saturation is hit, adding more substrate won't enhance the rate since all active sites are engaged.
- During reactions, substrate concentration declines over time, causing the reaction rate to drop.
Measuring Reaction Rates
- Initial reaction rate is the fastest during the process.
- Two methods for measuring enzyme activity include quantifying product formation and substrate depletion.
- Catalase is effective for measuring product appearance, particularly oxygen production.
- For substrate disappearance, amylase can be used to break down starch into maltose; starch presence can be monitored using iodine solution.
Experimental Methods
- For catalase, use water displacement in a measuring cylinder to collect produced oxygen.
- For amylase assays, periodically sample the reaction mixture and add iodine to detect starch breakdown, noting when the blue-black color disappears.
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Description
Explore the key factors influencing enzyme activity including temperature, pH, enzyme concentration, and substrate concentration. This quiz delves into how temperature changes can affect the rate of enzyme-controlled reactions and the concept of optimum temperature for enzymes.