4.4.1.1 Photosynthetic reaction Photosynthesis is represented by: Photosynthesis is an endothermic reaction. Energy is transferred from the environment to the chloroplast by 1 Ask students to recap KS3 and define the word equation for photosynthesis when given the reactants and products. Describe the method used to test a leaf for starch, including a risk assessment. Describe the need for chlorophyll and light for the photosynthetic reaction to occur. Students can test for starch in a green leaf compared to a variegated leaf or leaf kept in the dark. 4.4.1.2 Rate of photosynthesis Required practical: photosynthesis Investigate the effect of light intensity on the rate of photosynthesis using an aquatic organism such as pondweed. AT skills covered by this practical activity: biology The rate of photosynthesis may be affected by: temperature level of carbon dioxide light intensity amount of chlorophyll. 1 Describe the effects of temperature, light intensity and carbon dioxide concentration on the rate of photosynthesis. Draw graphs to illustrate the effect that changing these factors has on the rate of photosynthesis. Define limiting factor. Describe how to test the effects of changing light intensity on photosynthetic rate in pond weed. Required practical 3: investigate the effect of a factor on the rate of photosynthesis. Investigate the rate of photosynthesis with changing light intensity. Use numbers of bubbles of oxygen from Elodea or similar pondweed to measure the rate.
products and the relative amounts of energy transferred. 4.4.2.1 Anaerobic respiration Anaerobic respiration in muscles is represented by the equation: The energy transferred supplies all the energy needed for living processes. As the oxidation of glucose is incomplete in anaerobic respiration much less energy is transferred than in aerobic respiration. 1 Give students the products and reactants for anaerobic respiration and ask them to recap KS3 by putting them in the correct order. Compare this equation with the one for aerobic respiration. Write the word equation for anaerobic respiration. Students can investigate the time they can continue clenching and unclenching non-writing hand above and below the level of their heart. 4.4.2.1 Fermentation Anaerobic respiration in plant and yeast cells is represented by the equation: Anaerobic respiration in yeast cells is called fermentation and has economic importance in the manufacture of bread and alcoholic drinks. 1 Ask students to recap from KS3 and write a definition for fermentation. Write the word equation for fermentation. Investigate the amount of carbon dioxide produced from fermentation of yeast with varying amounts of sugar: Use three pre-made up solutions and add different food colourings to each to prevent confusion. Use water as a control. Use the change in the diameter of a balloon to measure amount of CO2 produced.
Incubate the yeast in a water bath. 4.4.2.2 Response to exercise During exercise the human body reacts to the increased demand for energy. The heart rate, breathing rate and breath volume increase during exercise to supply the muscles with more oxygenated blood. This is needed for the increased cellular respiration to transfer more energy to meet the demand. If insufficient oxygen is supplied anaerobic respiration takes place in muscles. The incomplete oxidation of glucose causes a build-up of lactic acid and creates an oxygen debt. During long periods of vigorous activity muscles become fatigued and stop contracting efficiently. One cause of muscle fatigue is the build-up of acid in the muscles. The oxygen debt must be ‘repaid’ once exercise stops causing deep breathing for some time. 1 Describe the changes in the body during and after exercise. Draw a cartoon strip to show the journey of an oxygen molecule from air through organs and blood to cell and mitochondrion with subsequent release of energy. Describe oxygen debt and how it is repaid through vigour breathing. Investigate the effect of exercise on the heart rate. Measure breathing and pulse rates before and after vigorous exercise. Use plasticine to model the molecule for lactic acid C3H6O3. Determine that if 6 oxygen are added, the resulting products are 3 lots of carbon dioxide (CO2) and water (H2O).