Photosynthesis.pdf

Photosynthesis- defn Series of enzyme-controlled chemical reactions where green plants produce food using sunlight In simpler terms-green plants use light to make carbohydrates Equation for photosynthesis-Need to know chemical and word equations! R...

Photosynthesis- defn Series of enzyme-controlled chemical reactions where green plants produce food using sunlight In simpler terms-green plants use light to make carbohydrates Equation for photosynthesis-Need to know chemical and word equations! Requirements for photosynthesis- 1. Carbon dioxide Enters plant as a gas from the atmosphere enters through stomata in the leaves (openings where gases can pass in and out) entrance by diffusion co2 is required because it supplies the element carbon which is required for the manufacture of glucose 2. Water- enters plant through root hairs from soil enters by osmosis travels to site of photosynthesis through xylem vessels water provides the hydrogen required for glucose manufacture 3. Chlorophyll- this green pigment is found in chloroplasts in plant cells it is a site where biochemical reactions occur it is the location where photosynthesis occurs 4. Sunlight- provides energy for chemical reactions no sunlight results in no energy for photosynthesis which results in no food made by the plant photosynthesis only occurs during daylight  Products and uses of photosynthesis- Glucose- 1. Burned in respiration to produce energy for the plant 2. Transported to where It is needed by the phloem vessels Oxygen- 1. Product of photosynthesis 2. Form of gas 3. If it is not needed by the plant for respiration, it diffuses out of the leaves through the stomata 4 LCQ-How is leaf adapted to function of gaseous exchange? 1. Stomata-found on upper and lower surface of leaves 2. Air spaces in mesophyll allow gases to move quickly and easily to and from palisade layer 3. Leaf is thin-gases get quickly to and from the leaf 4. Cells in leaf are moist-Gases are lubricated and dissolved in solution and can easily move through leaf 3 LCQ-How is leaf adapted to function of photosynthesis- 1. Palisade layer-has extra chloroplasts for maximum amount of photosynthesis 2. Leaf is flat-to increase surface area for sunlight to hit 3. All substances can be delivered to main site of photosynthesis(palisade layer) via vascular bundles in leaf and easily carried away also Recap- 1. Definition of photosynthesis- 2. Word eqn 3. Chemical eqn 4. Requirements for photosynthesis 5. Products of photosynthesis 4 6. Leaf adaptation gaseous exchange 3 7. Leaf adaptation photosynthesis  T Table if asked to compare 2 Stages of Photosynthesis- 1. Light stage 2. Dark stage Light stage 1. Needs light Light-dependent stage 2. Location-Granum of chloroplast Two pathways- 1. Cyclic photophosphorylation 2. Noncyclic photophosphorylation Dark stage 1. Does not need light Light independent stage 2. Location-Stroma of chloroplast CO2 6 Light stage-Pathway 1 – Cyclic Photophosphorylation - Described as cyclic because the energised electrons that leave the chlorophyll eventually return to the chlorophyll molecule having lost their energy - The chlorophyll absorbs light energy and passes it to an electron, which it then ejects as a high-energy electron - A compound called an electron accepter accepts this high-energy electron and then passes the electron to a series of molecules called the electron transport chain - As the electron passes along the chain, its excess energy is used to produce ATP. By the end of the chain, the electron has lost its excess energy and is now a low energy electron again - The electron returns to the chlorophyll - The ATP produced here is used in the light-independent stage Pathway 2 – Non-Cyclic Photophosphorylation - non-cyclic because the electrons that leave the chlorophyll are replaced by electrons from a different source. The chlorophyll pulls electrons from surrounding water molecules and causes them to break down in a process called photolysis - High energy electrons are passed to the electron transport chain, where they combine ADP and P to form ATP. The ATP is then used to produce glucose in the light- independent stage - The electrons that have passed through the electron transport chain are now low energy and these replace the high-energy electrons that have left the chlorophyll - Oxygen atoms are produced and pairs of these combine to form oxygen gas. This is either used immediately in respiration by the plant, or any excess oxygen diffuses out into the intercellular spaces and from there through the stomata into the atmosphere where it can be used in respiration by other organisms - Hydrogen atoms enter the proton pool. These hydrogen ions are then used in the light-independent stage to combine with CO to form glucose. 2 - NADP that has returned from the light-independent stage picks up two excited + electrons that were produced by chlorophyll and held by the electron acceptor. This produces NADP - NADP + 2e = NADP + - - The NADP then picks up a hydrogen ion from the proton pool to form NADPH - NADP + H = NADPH - + The NADPH then carries the H to the light-independent stage.  Light-independent Stage(Calvin stage) - Carbon dioxide from the atmosphere or from cellular respiration diffuses into the stroma - Hydrogen ions and electrons brought from the light stage by NADPH are added to the CO and form the carbohydrate glucose 2 - The NADPH turns back into NADP. This then returns to the thylakoid membrane to + form NADP again. - - Energy for the formation of glucose is supplied by ATP from both the cyclic and non- cyclic pathways of the light-dependent stage - As the ATP breaks down to ADP + P, energy is released - The ADP and P return to the electron transport chain to form more ATP What's the purpose of the stages? Note- 1. Cyclic- electron remove from the chlorophyll is the same electron returned to the chlorophyll 2. Photo- light is required 3. Phosphoyrlation-addition of phosphate molecule to another substance e.g ADP receives phosphate to become ATP 4. Noncyclic-the electron removed from chlorophyll is not the electron returned to the chlorophyll Structure of ATP- Formation of ATP from ADP- Experiment-investigate the effect of light intensity on rate of photosynthesis= Method- 1. Set up apparatus as shown in diagram 2. Record distance from the lamp to elodea 3. Wait 3 mins to allow elodea to adjust to light 4. Count no of oxygen bubbles released in one minute 5. Move lamp 6. Allow 3 mins for elodea to adjust to light 7. Count no of oxygen bubbles released in 1 min Result- Closer the lamp is to elodea the more oxygen bubbles are given off Conclusion- Increasing the light intensity increases rate of photosynthesis Thus more oxygen bubbles are given off per minute Notes-thermometer records the temperature of the water. There is an optimum temperature for photosynthesis as it is an enzyme controlled reaction=OT=25’C The water in the beaker could also be a solution of sodium hydrogen carbonate aka sodium bicarbonate as this ensures carbon dioxide will be in excess and never run out-CO2 cannot be a limiting factor LCQ-why aquatic and not terrestrial- 1. It will produce oxygen bubbles in water that can be clearly seen and counted -allowing for easy + accurate recording of rate of photosynthesis  What is happening at A? What is happening at B? Why? Why? What is a limiting factor? Anything that refrains a population from growing What is the limiting factor in this experiment? C02 LCQ-How to artificially enhance growth of plants in a greenhouse? 1. Pump in CO2 from cylinder 2. Use lamps on a timer to artificially increase daylight One method that does both- Fire lighting Variables in PS to increase/decrease- 1. Light 2. CO2-carbon to make glucose 3. Temp-enzyme controlled reaction Think to 2017 q anabolic steroids-small muscles to big muscles photosynthesis is anabolic