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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 heat means more kinetic energy, so the molecules move faster.

If the molecules move faster, what is more likely to happen?

<p>Enzymes are more likely to collide with the substrate molecules.</p> Signup and view all the answers

What also increases as a result of more heat?

<p>Energy of the collisions also increases.</p> Signup and view all the answers

If the energy of the collisions increases, what are the collisions more likely to result in?

<p>Collisions are more likely to result in a reaction.</p> Signup and view all the answers

What happens if the temperature gets too high?

<p>The reaction stops.</p> Signup and view all the answers

Explain why if the temperature gets too high, the reaction stops.

<p>A rise in temperature makes the enzyme molecules vibrate more, which can break bonds that hold the enzyme in shape, changing the active site's shape.</p> Signup and view all the answers

What does the enzyme become if the active site changes shape and the enzyme and substrate no longer fit?

<p>The enzyme becomes denatured.</p> Signup and view all the answers

What does the enzyme no longer function as if it becomes denatured?

<p>No longer functions as a catalyst.</p> Signup and view all the answers

What does every enzyme have?

<p>An optimum temperature.</p> Signup and view all the answers

What is the optimum temperature of most human enzymes?

<p>37 degrees Celsius.</p> Signup and view all the answers

What is the optimum temperature for some enzymes such as those used in biological washing powders?

<p>60 degrees Celsius.</p> Signup and view all the answers

What shows how the rate of reaction changes with temperature?

<p>Temperature coefficient - Q10.</p> Signup and view all the answers

What does the temperature coefficient value show?

<p>How much the rate of reaction changes when the temperature is raised by 10 degrees Celsius.</p> Signup and view all the answers

At temperatures before the optimum, what does a Q10 value of 2 mean?

<p>That the rate doubles when the temperature is raised by 10 degrees Celsius.</p> Signup and view all the answers

What does a Q10 value of 3 mean?

<p>The rate trebles when the temperature is raised by 10 degrees Celsius.</p> Signup and view all the answers

What is the Q10 value of most enzyme-controlled reactions?

<p>Around 2.</p> Signup and view all the answers

What does pH affect?

<p>Enzyme activity.</p> Signup and view all the answers

What do all enzymes have?

<p>An optimum pH value.</p> Signup and view all the answers

What pH do most human enzymes work best at?

<p>pH 7 - but there are exceptions.</p> Signup and view all the answers

What pH does pepsin work best at?

<p>Acidic pH 2 - useful because it's in the stomach.</p> Signup and view all the answers

What bonds hold the enzyme's tertiary structure in place?

<p>Ionic bonds and hydrogen bonds.</p> Signup and view all the answers

What happens above and below the optimum pH?

<p>The H+ ions and OH- ions found in acids and alkalis can mess up the ionic bonds and hydrogen bonds that hold the tertiary structure in place.</p> Signup and view all the answers

What happens to the enzyme's active site if the ionic and hydrogen bonds are affected?

<p>The active site changes shape.</p> Signup and view all the answers

What does the enzyme become if the active site changes shape?

<p>Denatured.</p> Signup and view all the answers

What does enzyme concentration affect?

<p>Rate of reaction.</p> Signup and view all the answers

What is more likely to happen if there are more enzyme molecules in a solution?

<p>The more enzyme molecules in a solution, the more likely a substrate molecule is to collide with one and form an enzyme-substrate complex.</p> Signup and view all the answers

Therefore, what does increasing the concentration of the enzyme increase also?

<p>Also increases the rate of reaction.</p> Signup and view all the answers

What happens if the amount of substrate is limited and you keep adding more enzyme molecules?

<p>It comes to a point when there's more than enough enzyme molecules to deal with the available substrate, so adding more enzymes has no effect.</p> Signup and view all the answers

What does substrate concentration affect?

<p>Substrate concentration affects the rate of the reaction up until a point.</p> Signup and view all the answers

What happens if the substrate concentration is increased?

<p>The rate of reaction increases.</p> Signup and view all the answers

Why does the rate of reaction increase if the substrate concentration is higher?

<p>More substrate molecules mean a collision between substrate and enzyme molecules is more likely, so more active sites will be used.</p> Signup and view all the answers

When does the rate of reaction stop increasing?

<p>When the 'saturation' point is reached.</p> Signup and view all the answers

Why does the rate of reaction stop increasing after the saturation point is reached?

<p>Because there are so many substrate molecules that all the active sites are full, so adding more substrate makes no difference to the rate of reaction.</p> Signup and view all the answers

What happens to substrate concentration over time during a reaction?

<p>Substrate concentration decreases over time during a reaction.</p> Signup and view all the answers

If the substrate concentration decreases over time and no other variables are changed in the reaction, what will happen to the rate of reaction?

<p>Rate of reaction will decrease over time too.</p> Signup and view all the answers

What is the highest rate of reaction during the reaction?

<p>The initial rate of reaction.</p> Signup and view all the answers

Name two ways you can measure the rate of an enzyme-controlled reaction.

<p>You can measure how fast the product of the reaction appears or the disappearance of the substrate to compare the reaction under different conditions.</p> Signup and view all the answers

What enzyme would you use to measure how fast a product appears?

<p>Catalase.</p> Signup and view all the answers

Why would catalase be a good example?

<p>Easy to collect the oxygen produced and measure how fast it's given off.</p> Signup and view all the answers

How would you measure the appearance of a product using catalase?

<p>Fill a large beaker with water and place an upside-down measuring cylinder inside, place one end of a delivery tube inside the upside-down measuring cylinder, place the hydrogen peroxide solution and catalase into a test tube, quickly place the other end of the delivery tube over the top of the test tube and measure how much oxygen is produced using the upside-down measuring cylinder.</p> Signup and view all the answers

What enzyme would you use to measure the disappearance of the substrate?

<p>Amylase - catalyses the breakdown of starch into maltose.</p> Signup and view all the answers

What solution would you use to detect starch?

<p>Solution of potassium iodide and iodine.</p> Signup and view all the answers

How would you time how long it takes for the starch to disappear?

<p>By regularly sampling the starch solution.</p> Signup and view all the answers

Why would you alter the conditions of the reaction?

<p>To compare rates.</p> Signup and view all the answers

Describe how you would use amylase to measure the disappearance of a substrate.

<p>Place the starch solution in a test tube and add amylase, every minute sample the mixture by using a pipette to take a sample and place it on the spotting tile, add the iodine in potassium iodide to the sample, time when the iodine solution no longer turns blue-black to note that starch has been broken down.</p> Signup and view all the answers

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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