2017 Photosynthesis Respiration STQ QP

2017 Photosynthesis and Respiration STQ 2017 / H2 / AJC PRELIM / P2 Q61In anaerobic respiration in yeast, the pyruvate molecules are broken down to produce ethanol and carbon dioxide. The release of carbon dioxide can be used to investigate the rate of anaerobic respiration. Fig. 6.1 shows an experiment which was set up to find the rate of anaerobic respiration. Fig. 6.1The meniscus moves down the tube as carbon dioxide is released. Table 6.1 shows the distance moved by the meniscus from the start point. This was recorded every 10 minutes. Table 6.1Time/ min0102030405060708090Distance travelled by meniscus from start point/ mm012591421457398 (a)The rate of anaerobic respiration can be calculated by using the rate of movement of the meniscus.Calculate the rate of anaerobic respiration between 70 and 80 minutes. You will lose marks if you do not show your working. [2(b)This experiment was repeated three more times. Each time, the glucose (a monosaccharide) was replaced with a different disaccharide sugar:

Maltose – a disaccharide of glucose and glucoseSucrose – a disaccharide of glucose and fructoseLactose – a disaccharide of glucose and galactose. Tables 6.2 (a), (b) and (c) show the results of these experiments. Table 6.2 (a): Using maltoseTime/ min0102030405060708090Distance travelled by meniscus from start point/ mm00000236912Table 6.2 (b): Using sucroseTime/ min0102030405060708090Distance travelled by meniscus from start point/ mm000131122374861Table 6.2 (c): Using lactoseTime/ min0102030405060708090Distance travelled by meniscus from start point/ mm0000000000With reference to the information provided in Tables 6.2 (a), (b) and (c) and your biological knowledge:(i)Describe the difference in the results for maltose and sucrose, and suggest one explanation for this difference, [2

(ii)Suggest two explanations for the results for lactose. [2(c)An electron micrograph of yeast, Candida albicans, is shown in Fig. 6.2. Fig. 6.2(i)On Fig. 6.2, label site of i.Glycolysisii.Oxidative phosphorylation[2(ii)State one visible structure of mitochondria from Fig. 6.2 and describe how it supports mitochondria’s function. [1

(ii)Besides location, compare between oxidative phosphorylation and photophosphorylation. [4] [Total: 13 marks]

2017 / H2 / CJC PRELIM / P2 Q62Microalgae have been extensively studied for various purposes, such as the production of biomass as a source of valuable chemicals of health foods and for wastewater treatment. Recently, microalgal photosynthesis was considered to be an effective means to reduce the emission of carbon dioxide, a major greenhouse gas, in the atmosphere. Light is the most important factor affecting microalgal photosynthesis kinetics. In general, most microalgal mass culture systems are limited by light, because light is easily absorbed and scattered by the microalgal cells. Therefore, understanding and quantification of light dependence of microalgal activity is of great importance in designing an efficient photobioreactor, in predicting process performance, and in optimizing operating conditions.Fig. 6.1 The volumetric photosynthetic activity as a function of incident light intensity at different light types and cell concentrations. Data points and error bars were average values and standard deviations of three replicated experimental results. Solid lines represent the calculated results from the photosynthesis–irradiance model. The light types and cell concentrations were: () simulated daylight and 0.215 g L−1; ( ) simulated daylight and 0.123 g L−1; ( ) red light and 0.123 g L−1; and () green light and 0.123 g L−1.Jeon et al 2005 Measurement of microalgal photosynthetic activity depending on light intensity and quality. Biochemical Engineering Journal 27 (2005) 127–131 (a)Explain the trends seen when red, green and daylight (at 0.123gL-1) are compared. ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………

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Fig. 6.2 shows a schematic showing the functional relationship between light harvesting complexes (LHC) and photosystems II & I. Regulatory complexes are also shown comprising of kinases and the regulation of excess energy between PS II and I. Gollan et al 2015 Photosynthetic light reactions: integral to chloroplast retrograde signalling. Current Opinion in Plant Biology 27:180-191modified.Fig. 6.2(b)Explain what is the LHC and its role in photosynthesis. …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….[2](c)With reference to Fig. 6.2 explain the role of electrons in the photosynthesis as they move from Photosystem II to Photosystem I. …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….[3](d)With reference to Fig. 6.2 suggest the implications of the role of LHC and PSII core protein phosphorylation from Photosystem II to Photosystem I. …………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………………….[3]

[Total: 13]

2017 / H2 / DHS PRELIM / P2 Q8Question 3Studies were carried out on soil-dwelling aerobic bacteria. Soil samples were taken at two depths, A and B. The samples were taken at intervals over six years to determine the activity of dehydrogenases, involved in the Krebs cycle.Fig. 8 shows the mean dehydrogenase activity of the bacteria in these samples. Fig. 8(a)(i)Explain the importance of Krebs cycle dehydrogenase in ATP synthesis. [3] (ii)With reference to Fig. 8 and your knowledge on enzymes, explain which samples, A or B, were taken from a greater depth. [4]

(b)Dehydrogenase is also required for anaerobic respiration. Describe the process catalysed by the lactate dehydrogenase. [2] (c)Photosynthetic bacteria can be found in the ocean. Samples of bacteria were collected at the same depth from different locations and the activity of the enzyme RUBISCO was studied. Results obtained show that the samples collected near factories had higher RUBISCO activities than samples collected near forests. (i)Identify the factor which explains the differing result. [1]