2017 Photosyntheis Respiration STQ MS

2017 Photosynthesis and Respiration STQ MS2017 / 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 and 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. Rate of Anaerobic Respiration = (73-45) mm / (80-70) min= 28 mm / 10 min= 2.8 mm min-1[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 glucoseSucrose – a disaccharide of glucose and fructoseLactose – a disaccharide of glucose and galactose. Tables 6.2 (a), (b) and (c) show the results of these experiments. Table 6.2 (a): Using maltose

Time/ 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, Glucose is the respiratory substrate for glycolysis;Maltose: meniscus only starts moving at 50 min vs sucrose at 30 min/ movement of sucrose more than maltose + data;Enzyme to break down sucrose is more readily available/at higher concentration than enzymes to break down maltose;[2(ii)Suggest two explanations for the results for lactose. Yeast does not have proteins channels that allows uptake of lacotse;Yeast does not encode for lactase that breaks down lactose to glucose and galactose;AVP;[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. Highly folded inner membrane + Increase surface area for embedment of more ETC/ ATP synthase to increase rate of ATP productionMembrane bound/ double membrane + Enclose matrix that contains enzymes for link reaction and Kreb’s cycle/ compartmentalizes matrix for optimum conditions for enzymes to work; [1(ii)Besides location, compare between oxidative phosphorylation and photophosphorylation. [4FeaturesOxidative phosphorylationPhotophosphorylationFunctions in the presence of..oxygenlightSource of energyNADH and FADH2lightNo. of electron transport chain 12Electron flowlinear – one-waylinear or cyclic Final electron acceptoroxygenNADP (non-cyclic) PSI reaction center (cyclic) Involvement of waterwater producedphotolysis of water Establishment of proton gradient protons pumped outwards from matrix across inner mitochondrial membrane into intermembrane spaceprotons pumped inwards from stroma across thylakoid membrane into thylakoid space ProductsATP, waterATP, NADPH, oxygen [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.

(a)Explain the trends seen when red, green and daylight (at 0.123gL-1) are compared. ANS [L2] Novel [5]1.Comparing at 1500µEm-2s-1 red light yields the highest Photosynthetic rate 5.5 mgL-1h-1 due to the presence of P680 and P700 absorbing best at those wavelengths.2.Comparing at 1500µEm-2s-1 Green light yields 3.0 mgL-1h-1 the lowest absorption as green light is reflected.3.Comparing at 1500µEm-2s-1 daylight yields a moderate Photosynthetic rate 4.5 mgL-1h-1 due to the presence of P680 and P700 but subject to the efficiency of light capturing.4.General trend within graph, at low light intensity, all three showed that Light was a Limiting Factor.5.At higher intensities there is a plateau in all three graphs where light is no longer a limiting factor.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. ANS [L1] Novel [2]1.LHC is the Light Harvesting Complex comprising mainly of Carotenoids and special chlorophyll;2.Role is to consolidate / channel energy to the photosystems in this way helps in the promotion of electrons within Photosystems;(c)With reference to Fig. 6.2 explain the role of electrons in the photosynthesis as they move from Photosystem II to Photosystem I.

ANS [L1] Novel [3]1.electrons are of a higher energy state once promoted, are then passed down the ETC where energy lost in the transfer is used to pump protons into the thylakoid space;2.Chemiosmosis of H+ then drives the synthesis of ATP using ATP synthase. ATP will then be used in the Calvin cycle.3.Electrons passed from PSII through the ETC reach and replenish PSI. (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. ANS [L3] Novel [3]1.LHC and PSII core protein help with the distribution of energy between PSII and PSI.2.At high light intensity there is a redistribution of energy so that bleaching does not occur.3.At low light intensities, there is a channeling of energy so that photosynthesis will continue.[Total: 13]2017 / H2 / DHS PRELIM / P2 Q8Question 8(a) (i)Dehydrogenase reduces NAD+ to NADHwhen isocitrate is converted to α-ketoglutarate / succinyl-CoA; OR when malate is converted to oxaloacetate. NADH carries the electron and proton to electron transport chain for ATP synthesis via oxidative phosphorylation. ORDehydrogenase reduces FAD2+ to FADH2 when succinate is converted to fumerate.FADH2 carries the electron and proton to electron transport chain for ATP synthesis via oxidative phosphorylation.(a)(ii)Depth BMean dehydrogenase activity was lower, ranging from 1.5-2.5AU, while that of depth A was higher, ranging from approximately 3.2-5.5AU. At a greater depth, oxygen concentration is lower. Hence, rate of oxidative phosphorylation is lower. Regeneration of NAD+ / FAD2+ is slower hence there is lesser substrates for effective collision. (b)lactic acid fermentation