Enzymes & Metabolism (HL IB Biology)

The four statements below are examples of the two types of metabolism, anabolism and catabolism.

Which one of the statements represents a type of metabolism which is different to the other three options?

The graph shows the effect of enzyme concentration on the rate of an enzyme-controlled reaction. The substrate concentration is constant.

Which statement about the graph is correct?

The following statements apply to enzyme-catalysed reactions. Which row of the table best describes the sequence of events in an anabolic reaction?

The graph shows the course of an enzyme-catalysed reaction at 25 °C.

Which statement about the graph is incorrect?

Which statement below best describes the concept of enzyme-substrate specificity?

When investigating the rate of reaction of the enzyme lipase on the hydrolysis of triglycerides, the pH must be maintained to prevent the lipase denaturing.

Why might fluctuations in pH occur?

The breakdown of hydrogen peroxide to water and oxygen is catalysed by the enzyme catalase. In an investigation into the effect of temperature on the rate of reaction of catalase, mashed liver (which contains catalase) was added to hydrogen peroxide.

What would the independent variable be in this experiment?

Which of the following statements about enzymes is not correct?

A bacterial enzyme from the species Caldicoprobacter algeriensis can be immobilised onto polymethacrylate beads for the conversion of glucose into fructose in the food industry, as shown in the diagram below.

What is the name of the enzyme that is immobilised on the polymethacrylate beads?

Enzymes can be immobilised in various ways. The diagram below shows two different ways of immobilisation. 

Immobilised lactase enzymes are used to make milk digestible for lactose intolerant people.  A student carried out an investigation to compare the activity of the enzyme lactase that had been immobilised in the two different ways shown. 

A solution containing 50 mg cm^–3 of lactose was poured through a column containing the immobilised enzyme.

What would be the best choice of dependent variable for this experiment?

A student wished to use a starch solution of 0.01% for an enzyme experiment. A stock solution of 1.0% starch solution was provided. 

Which of the following dilutions would be the best method to achieve the desired concentration with greatest precision, using standard laboratory equipment? 

Which of the following statements about metabolism are correct?

1. Metabolism involves chemicals called metabolites.
2. Metabolism involves reactions in a linear chain.
3. Metabolism involves reactions in a cycle.
4. Metabolism involves only the breakdown of molecules.

The graph below shows the energy changes during a reaction.

What effect would adding an enzyme have on the energy changes of the reaction?

What is the difference between a competitive and non-competitive inhibitor?

Cyanide ions are an example of an allosteric inhibitor that targets the enzyme cytochrome c oxidase in aerobic respiration.

Which row best describes the action of cyanide ions?

Isoleucine can be described as an end-product inhibitor.

Which statement best describes the action of isoleucine?

Which graph shows the rate of a reaction taking place in the presence of a competitive inhibitor compared to the rate of a reaction in the absence of an inhibitor?

The table below gives information on the rates of several enzyme-catalysed reactions.

Which enzyme catalyses the reaction with the fastest rate of product formation?

Which statement best describes how to calculate the initial rate of a reaction from a graph such as the one below?

The activity of two types of protease enzymes was measured in two different species of fish; species X and species Y. Protease enzymes are responsible for breaking down proteins into amino acids. The results of the research are shown in the graph.

The unit U denotes the enzyme required for the production of 1 μmol of product per minute. The bars represent the standard deviation.

Which statement about protease enzymes is correct?

The following graph shows the change in energy that occurs during an enzyme catalysed reaction.

Which of the following would be the most accurate description of this graph?

Beetroot (Beta vulgaris) is a root vegetable with a characteristic red colour that is due to the pigment betanin found within the vacuoles of beetroot cells.

Scientists investigated the effect of temperature on the release of betanin from the beetroot cells. This was recorded as the mean absorbance when using a colorimeter, with a higher absorbance indicating more pigment released. The scientists deduced that the pigment is released when the membrane proteins of the tonoplast surrounding the vacuole denature.

The graph below shows their results.

Which of the following descriptions would best explain the point where enzymes start to denature inside the beetroot cells?

Scientists extracted enzymes from different parts of the digestive tract of a mammal. The containers of enzyme samples got mixed up with each other before the scientists could label them. In order to identify the enzymes, they monitored the enzyme activity of each sample at different pH levels to determine the optimum pH for each.

The graph below shows the results for two of the samples (X and Y).

Which of the following would be the most valid conclusion that the scientists can draw from these results?

β-glucosidases are a diverse group of enzymes which hydrolyse glycosidic bonds and are present in a wide variety of organisms. One of their uses in the food industry is the hydrolysis of bitter compounds during juice extraction to increase the sweetness of the final product. These enzymes are often immobilised when used in the food industry to increase production and save on costs.

Scientists compared the activity of free β-glucosidase to that of immobilised β-glucosidase over a range of different temperatures. Their results are shown in the graph below.

Which of the following would be the most valid comparison between free and immobilised β-glucosidase?

Students investigated the effect of starch concentration on the activity of amylase. 

1. They used a 1% starch solution and made two dilutions of 0.1% and 0.01%
2. They added 10 cm³ of amylase to each of the three test tubes
3. They took samples of each solution at 10 second intervals for 30 seconds in total
4. Iodine solution was added to each sample to test for the presence of starch
5. They came to the conclusion that the amylase did not properly break down the starch

Their teacher suggested that the students could achieve some more useful results by making some simple improvements to their experimental design.

Which of the following would represent the best improvements to their experimental design?

This diagram shows a metabolic pathway occurring in an organelle. The speed of this metabolic pathway is self-regulating as the end product acts as a competitive inhibitor to enzyme 2. 

What would you expect not to occur when adding an additional end product to the organelle?

In the graph, Z represents the relationship between the initial rate of an enzyme-catalysed reaction and the concentration of its substrate under optimal conditions and without an inhibitor.

Which curve would represent the same experiment carried out in the presence of a low concentration of a non-competitive inhibitor?

The graphs in A - D show the progress of an enzyme-catalysed reaction, measured by the volume of product released from the reaction mixture over time. 

Which graph best depicts how a scientist would establish the average rate of reaction over the first minute of the reaction?

The enzyme catalase was added to a large volume of hydrogen peroxide solution. The volume of oxygen produced in the first five seconds was measured at 250 cm³. 

What is the initial rate of reaction in dm³ min^-1 ?