Some animals live in cold places. They sometimes huddle together as shown in Fig. 1.1. You are going to investigate the effect of huddling on heat loss from model animals. Test-tubes filled with hot water will represent the animals. Read all the instructions but DO NOT DO THEM until you have drawn a table for your results in the space provided in 1(a)(i). You should use the safety equipment provided while you are doing the practical work. Raise your hand when you are ready for hot water to be poured into the beaker that is wrapped in foil. Step 1 Half-fill one test-tube with hot water and place it in the empty beaker. Step 2 Put the thermometer into the test-tube containing hot water. Step 3 Measure the temperature of the hot water in the test-tube. Record this temperature in your table in 1(a)(i). Step 4 Leave the thermometer in the test-tube and start the stop-clock. Step 5 After one minute, measure the temperature of the hot water in the test-tube. Record the temperature in your table in 1(a)(i). Step 6 Measure and record the temperature of the hot water in the test-tube every minute for a total of five minutes. Step 7 Remove the thermometer from the test-tube and carefully empty the water from the test-tube into the beaker labelled waste. Step 8 Place three test-tubes together and keep them together with the elastic band, as shown in Fig. 1.2. Step 9 Place the group of three test-tubes into the empty beaker. Half-fill all three test-tubes with hot water. Step 10 Place the thermometer into any one of the three test-tubes. Step 11 Repeat step 3 to step 7 with this group of three test-tubes. Step 12 Remove the elastic band from the group of three test-tubes. Make a group of seven test-tubes and keep them together with the elastic band, as shown in Fig. 1.3. Step 13 Place the group of seven test-tubes into the empty beaker. Half-fill all seven test-tubes with hot water. Step 14 Place the thermometer into the central test-tube. Step 15 Repeat step 3 to step 7 with this group of seven test-tubes. In mammals, respiration releases heat energy to maintain an optimum temperature for enzyme activity in the body. Amylase is an enzyme that catalyses the breakdown of starch into reducing sugars. Plan an investigation to identify the temperature at which the enzyme amylase is most active.

Biology

IGCSE&ALevel

CAIE

Exam No：0610_s23_qp_52 Year：2023 Question No：1(b)

Answer:

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12.2.1 Define aerobic respiration as the chemical reactions in cells that use oxygen to break down nutrient molecules to release energy

12.2.2 State the word equation for aerobic respiration as glucose + oxygen → carbon dioxide + water

12.2.3 Investigate the uptake of oxygen by respiring organisms, such as arthropods and germinating seeds

12.2.4 State the balanced chemical equation for aerobic respiration as

12.2.5 Investigate the effect of temperature on the rate of respiration of germinating seeds

5.1.1 Define the term catalyst as a substance that increases the rate of a chemical reaction and is not changed by the reaction

5.1.10 Explain the effect of changes in temperature on enzyme activity in terms of kinetic energy, shape and fit, frequency of effective collisions and denaturation

5.1.11 Explain the effect of changes in pH on enzyme activity in terms of shape and fit and denaturation

5.1.2 Define enzymes as proteins that function as biological catalysts

5.1.3 Describe why enzymes are important in all living organisms in terms of reaction speed necessary to sustain life

5.1.4 Describe enzyme action with reference to the complementary shape of an enzyme and its substrate and the formation of a product (knowledge of the term active site is not required)

5.1.5 Investigate and describe the effect of changes in temperature and pH on enzyme activity

5.1.6 Investigate and describe the effect of changes in temperature and pH on enzyme activity

5.1.7 Investigate and describe the effect of changes in temperature and pH on enzyme activity

5.1.8 Explain enzyme action with reference to the active site, enzyme-substrate complex, substrate and product

5.1.9 Explain the specificity of enzymes in terms of the complementary shape and fit of the active site with the substrate

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Solution:

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