Enzymes Practice Questions

Name the part of the enzyme labelled A.

Which term describes the molecule labelled B?

• A catalyst
• B enzyme
• C product
• D substrate

Name the structure labelled C.

Complete the table by filling in the four boxes labelled (i) to (iv).

Give one safety precaution the student should take when carrying out these food tests.

Name the type of molecule produced when a carbohydrate such as starch is broken down.

Name the two products formed when a lipid is broken down.

Name the molecules produced when a protein is broken down.

Enzymes are described as biological catalysts.

Explain what is meant by the term biological catalyst.

The rate of reaction can be calculated using

$$\text{rate} = \frac{1}{\text{time in seconds}}$$

Calculate the rate of reaction at 40 °C.

.............................................................. s$^{-1}$

Explain the results obtained between 10 °C and 40 °C.

Explain why the milk stayed cloudy at 60 °C.

State the independent variable and the dependent variable in this investigation.

Explain how the student can tell, using the spotting tile, when all the starch has been broken down.

Give two variables that should be kept the same in this investigation.

Describe the effect of sucrose concentration on the rate of reaction shown in the table.

Explain why the rate of reaction does not increase above a sucrose concentration of 20 g dm$^{-3}$.

The scientist repeated the investigation at a sucrose concentration of 30 g dm$^{-3}$ using twice the concentration of invertase.

Predict the effect this would have on the rate of reaction and give a reason for your prediction.

Calculate the energy transferred to the water.

.............................................................. J

Calculate the energy content of the cheese puff in kJ per gram.

Give your answer to 2 decimal places.

.............................................................. kJ per gram

The manufacturer states that the energy content of the cheese puff is 22.00 kJ per gram.

Suggest two reasons why the student's value is much lower than this.

Name the small molecules that enzymes join together to make a protein.

Plant cells make starch from glucose. This reaction is catalysed by an enzyme.

Explain how this enzyme catalyses the synthesis of starch.

The enzyme that joins glucose molecules together cannot join amino acids together.

Explain why.

Use the table to give the optimum pH of enzyme P and the optimum pH of enzyme Q.

Explain why the rate of reaction of enzyme Q is 0.0 at pH 2.

One of these enzymes is found in the stomach, where the pH is about 2.

Identify this enzyme and use the data to give a reason for your choice.

Identify the anomalous result in the table and calculate the mean time at pH 6, ignoring this result.

.............................................................. s

The rate of reaction can be calculated using

$$\text{rate} = \frac{1}{\text{mean time in seconds}}$$

Calculate the rate of reaction at pH 7. Give your answer to 3 decimal places.

.............................................................. s$^{-1}$

The student concluded that the optimum pH for amylase is exactly pH 7.

Evaluate the student's method and suggest three improvements that would make this conclusion more valid.

Figure 3 shows how the rate of an enzyme-controlled reaction changes as the temperature is increased. The optimum temperature for this enzyme is 40 °C.

Explain the shape of the graph shown in Figure 3.

State the food molecules present in sample B.

Compare what the Benedict's test results show about samples A and C.

A student repeated the Benedict's test on sample A but did not place the tube in a hot water bath. The solution stayed blue.

Explain why the student should not conclude that sample A contains no reducing sugar.