Factors affecting enzyme activity

All living cells contain enzymes.

Describe the role of enzymes in cells.

The table lists some enzymes, where they are produced and their function. Complete the table by giving the missing information.

Explain how changes in temperature affect the activity of an enzyme.

A student uses this method to investigate the effect of temperature on the digestion of lipid. Step 1 Add five drops of an indicator to a test tube. Step 2 Add 5 cm³ of milk to the test tube. Step 3 Then add 7 cm³ of sodium carbonate solution to the test tube. Step 4 Place a thermometer in the test tube, put the test tube in a water bath and leave it until the contents reach a temperature of 20 °C. Step 5 Add 1 cm³ of lipase solution to the test tube and start a timer. Step 6 Stir the contents of the test tube. Step 7 Record the time it takes for the indicator to change colour. The student then repeats these steps using water baths at five higher temperatures, increasing the temperature by 10 °C each time.

Name the independent variable in the student’s investigation.

Identify two variables that the student controls in his investigation.

Give the reason for including step 6.

Sodium carbonate solution is an alkali that turns the indicator pink in step 3. Explain why the indicator changes colour in step 7.

Sketch a graph on the axes to show the results you would expect the student to obtain.

Explain the effect of temperature on the time taken for the indicator to change colour.

Describe the role of bile in the digestion of lipid.

A student investigates the movement of substances from the gut into the blood using a model. The Visking tubing bag represents the gut and water represents the blood. Visking tubing is permeable to small molecules.

The student puts different solutions of various substances into the bag. After 20 minutes he carries out food tests on the water.

Complete the table to show the results obtained by the student. One has been done for you.

Explain how the volume of the bag would change when it only contains starch solution.

Describe the test the student should use to find out if glucose is present in the water.

Explain how you could use this apparatus to investigate the effect of bile on the digestion of lipid.

Yeast is an organism used in the production of beer. The diagram shows a yeast cell.

Give the letter of the part made of chitin.

Give the letter of the part that contains glycogen.

Yeast releases carbon dioxide when beer is made. A student uses this apparatus to measure the rate of carbon dioxide production by yeast.

The solution contains yeast cells. Name two substances in the solution.

Every three minutes, the student records the position of the drop of ink using the scale. The table shows the student’s results.

Calculate the difference between the rate of carbon dioxide production in the first three minutes and the rate in the final three minutes. Show your working.

difference in rate =_........ mm per minute

The student then investigates the effect of temperature on the rate of carbon dioxide production by yeast. He measures the volume of carbon dioxide produced rather than the distance moved by the drop of ink. The graph shows his results.

Give the optimum temperature for the production of carbon dioxide.

Explain why the rate of carbon dioxide production is slow at low temperatures.

Suggest how the student could modify the apparatus to vary the temperature.

Biological washing powder contains enzymes to remove stains from clothes. Describe an investigation to find the temperature at which biological washing powder is most effective at removing stains. Your answer should include experimental details and be written in full sentences.

Plants obtain their nutrition by photosynthesis.

Write the balanced chemical symbol equation for photosynthesis.

Explain how the rate of photosynthesis is affected by changes to abiotic (non-living) factors throughout the day.

Explain how very high temperatures might reduce the growth of plants.

A student wants to make yoghurt. The diagram shows what she did.

Which two stages help to improve the production of yoghurt by killing bacteria that compete with Lactobacillus ?

Explain why the milk needed to be cooled to 45 °C in stage 3.

Explain what could happen to the production of yoghurt if the jars used in stage 5 had not been sterilised in stage 2.

Explain what would happen to the production of yoghurt if the water cooled below 35 °C in stage 6.

The student added fruit to her yoghurt to improve the taste. Suggest how adding fruit to yoghurt also helps to maintain healthy skin.

A student is given a Petri dish containing starch mixed with agar jelly. The student makes five wells each of diameter 10 mm in the agar. She fills the wells with solutions of amylase, each with a different pH. After 24 hours she pours iodine solution on to the agar jelly. The iodine solution turns the starch in the agar jelly a dark blue colour. The diagram shows the appearance of the Petri dish.

The student measures the clear area around each well using a ruler. Two have been done for you. Complete the remainder of the table.

Explain why there is a clear zone around some of the wells containing amylase.

Explain why the clear zones have a range of different diameters. The diameters of the wells do not change during the experiment.

Name the independent variable in this investigation.

The student keeps the Petri dish at 20 °C to control the temperature in order to make a valid comparison between each pH. Name three other variables that the student needs to control.

The student repeats the experiment, keeping the Petri dish at 37 °C on this occasion. On the diagram, draw the results you would expect to see.

The diagram shows a model of an industrial fermenter used to study how changes in conditions can affect the yield of products.

An acid or alkali can flow through the acid/alkali inlet to maintain a constant pH within the fermenter. Explain why the pH needs to be kept within a narrow range.

Parts of the fermenter responsible for regulating the temperature are not shown in the diagram. Name two of these parts.

This fermenter uses a sparger to introduce air into the fermenter. Suggest why it is important to introduce air into the fermenter.

Before being used the empty fermenter is cleaned using steam. Suggest why.

The graph shows the time taken for samples of blood to clot at different temperatures.

When blood clots, an enzyme converts a soluble plasma protein into an insoluble plasma protein. Use the information in the graph to suggest the optimum temperature for this enzyme.

Explain why blood takes longer to clot at 20C than it does at 30C.

Use your knowledge of enzymes to explain why blood is slow to clot at 45C.

The coronary artery supplies blood to heart muscle cells. A heart attack may occur if the coronary artery is blocked by a blood clot. Suggest what happens in heart muscle cells when the coronary artery is blocked.