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Photosynthesis Which is more important? The carnivore or the plant? Introduction – Ecosystems: • A self-sufficient system consisting of a community of interacting organisms and the abiotic factors of their habitat – What does self-sufficient mean? • The organisms are interdependent and ALL rely on Producers – Producers are autotrophs – There are two types of autotrophs • Photosynthetic: plants, phytoplankton and some bacteria • Chemosynthetic: some bacteria: synthesis organic molecules using energy released from exergonic reactions – Where do you find chemoautotrophs and why? Photosynthesis 6CO + 6H O C H 2 2 6 12O6 + 6O2 • What is reduced? – CO2 (H atoms are added, or it is fixed (incorporated into organic molecules) • What type of energy change reaction is happening? – Endergonic reaction, the products are at a higher energy level than the reactants. • Where does the energy come from? – Light Two important molecules ATP – Reduced NADP - Adenosine triphosphate = Universal energy currency Nicotinamide adenine dinucleotide phosphate = Reducing power Photosynthesis • 6CO2 + 6H2O C6H12O6 + 6O2 • Where does the H come from to reduce the CO2? – From water. • So what has to happen to the water? What is this process called? • Photolysis: splitting of water using light energy • Glucose is a chemical energy store. What happens to it during respiration? – Energy is released when it is oxidised during respiration Importance of Photosynthesis – Why is it so important? • Energy from the sun is trapped by autotrophs and can then be passed along food chains – Other than respiration, what is glucose used for in plants? • Cellulose, starch, proteins, lipids, phospholipids, DNA, RNA (add to balanced symbol equation of photosynthesis- showing what happens after photosynthesis) – Cellulose, starch and lipids need no additional elements (they also consist of C, H and O)What is needed to produce • proteins? – Nitrates (sulphur for some amino acids) • Phospholipids? – Phosphates • DNA and RNA? – Both Nitrates and Phosphates – What happens to O2? What is the significance of this? – It is released as a waste product: the composition of atmospheric gases has changed as a result of photosynthesis: this makes aerobic respiration possible Leaf structure– Where does most photosynthesis take place? • In palisade layer of the leaf – Review how a leaf is adapted to its function. – Complete Activity 5.06a- Leaf Structure NADP • Nicotinamide adenine dinucleotide diphosphate – A co-enzyme – Works together with enzymes in processes like photosynthesis and respiration where there are lots of steps (and enzymes) involved – Has two forms: an oxidised and a reduced form – Oxidised: NADP (oxidised) or NADP+ – Reduced: NADP (reduced) or NADPH2 – Are electron transfer molecules: transferring e- from 1 molecule to another How photosynthesis works Light dependent stage Light independent stage Reactants Products Water, oxidised NADP, ADP and Pi Reduced NADP, ATP, and carbon dioxide Reduced NADP, ATP, Oxygen Glucose, oxidised NADP, ADP and Pi Photolysis using light energy Reduction of CO2 Reactions + The two stages of Photosynthesis – Where does the Hydrogen come from to reduce the CO2? • from the photolysis of water. – Do CO2 and water make direct contact so that the H can be transferred from the water to CO2? Explain. • No, the reduced co-enzyme NADP transfers the H – What transfers the energy from light to the carbohydrate fuel glucose? • ATP and reduced NADP • Complete Activity 5.06b Summary of Photosynthesis (Q14) • Q 5.12 Light Dependent reactions-pages 18-20 – What is a pigment? Which pigment is involved in photosynthesis? • Absorbs light at certain wavelengths and reflects all other wavelengths of light • Chlorophyll is the main one, but there are other pigments Which colours are absorbed? Reflected? 5.06c- Light Reactions Complete # 1-3 Extension 5.3 Light Dependent Reactions Read the top paragraph As well as chlorophyll accessory pigments are present too: They absorb light and pass energy onto chlorophyll The reaction takes place where the chlorophyll is. What is a photosystem? Arrangement of photosynthetic pigments in the membrane Two Photosystems• Photosystem I where chlorophyll absorbs at 700nm wavelength • Photosystem II where chlorophyll absorbs at 680nm wavelength • Identify with an arrow the higher energy level • Identify the light striking the photosystems. • Label the electron carriers • What happens when light is absorbed by the chlorophyll in the reaction centre? • Where in plant cell is the electron transport chain? • What is the purpose of the electron transport chain? Define photophosphorylation • Add the NADP and reduced NADP to the diagram. Compare the diagram above with figure 5.22. • Where did the electrons and H+ ions come from? Extension 5.3 Light Dependent Reactions for the more ambitious. – Compare cyclic and non-cyclic photophosphorylation• What happens to the electrons in– Cyclic – Non-cyclic • Reactants and Products? – Cyclic – Non-cyclic • Answer # 1-6 Chemiosmosis read page 21 • As electrons pass along the electron carriers, energy released is used to pump H+ into the thylakoid space. • H+ concentration builds up, pH drops to about 5 • There is now a pH gradient between inside the thylakoid space and the stroma, which is about pH 8. • Chemiosmosis then happens, H+ ions diffuse across the selectively permeable thylakoid membrane down a concentration gradient back into the stroma. This diffusion powers the phosphorylation of ADP via ATP synthase. Photosynthesis video. Use light dependent first part only. https://www.youtube.com/watch?v=joZ1EsA5_NY • How do the pair of elections move from the chlorophyll to the electron transport system? • How are the electrons lost from the chlorophyll replaced? • How is ATP synthesized when electrons pass between b and c? • NADP is not shown here. What is its role in the light dependent stage of photosynthesis? Light independent reactions 1. Carbon fixation. CO2 converted to organic carbon. Carried out by RuBisCo enzyme. 2. Reduction. H is added by NADPH made during the light reactions. Requires energy input ie. ATP. 3. Regeneration of RuBP. Requires ATP. Therefore the cycle can begin again. Light independent reactions- Read pages 22- 24 http://www.science.smith.edu/departments/Biology/Bio231/calvin.html Complete Activity 5.06d The Calvin Cycle Simplified Calvin Cycle Activity 5.6 How Calvin won the Nobel Prize • What was the aim of the experiment? • What is Chlorella? • Why was radioactive C added? Can be visualized using photographic film Activity 5.6 How Calvin won the Nobel Prize • How did he identify what had been produced? Chromatography Complete # 1-5. Simplified Calvin Cycle Chloroplasts • Animal cell ultrastructure – sER, rER, golgi, nucleus, nucleolus, ribosomes, lysosomes, mitochondria, membrane, centrioles • What are the differences between plant and animal cells? – Cell wall, vacuole, amyloplasts, no centrioles, chloroplasts, pits, plasmodesmata • Box on page 24 Lumen Limiting Factors – Define limiting factors• the factor which limits the rate of photosynthesis, as this factor increases the rate of photosynthesis increases and vice versa, this factor is furthest from its optimum. – List some factors which COULD be limiting in photosynthesis? • CO2 conc, light intensity, temperature, water supply Limiting Factors • For each of the factors below sketch a graph of its affect on the rate of photosynthesis – Light intensity – Carbon dioxide concentration – Temperature – Light wavelength – Water availability- too complex to graph as water is involved in many processes Do you think that there is a link between productivity and biodiversity? Biodiversity hotspots around the world.