GCSE Biology 1.5 Plants and Photosynthesis Knowledge Organiser PDF

# GCSE Biology 1.5 Plants and Photosynthesis Knowledge Organiser ## Photosynthesis - A series of enzyme-controlled reactions in plant cells - Chlorophyll absorbs light energy for the reaction - The leaf is the organ of photosynthesis - Sunlight + Water (from roots) + Carbon Dioxide (from air) →...

# GCSE Biology 1.5 Plants and Photosynthesis Knowledge Organiser ## Photosynthesis - A series of enzyme-controlled reactions in plant cells - Chlorophyll absorbs light energy for the reaction - The leaf is the organ of photosynthesis - Sunlight + Water (from roots) + Carbon Dioxide (from air) → Glucose + Oxygen (a byproduct) ## The Leaf (Separate Science Only) - **Cuticl**e - **Upper Epidermis** - **Palisade Layer** - **Spongy Layer** - **Stomata** - **Xylem and Phloem** ## The Importance of Water (Separate Science Only) - Water is used in photosynthesis, transport of minerals and provides support by filling the cell vacuoles which push against cell walls. - This keeps cells turgid and prevents cells becoming flaccid and wilting. ### Leaf - Water from the xylem evaporates into air spaces. - Some water vapour is lost from the stomata. - This is transpiration. ## Factors Affecting Photosynthesis - Limiting Factors ### Temperature - The rate of photosynthesis is usually measured by recording the volume of oxygen produced. - As photosynthesis is controlled by enzymes, as the temperature increases the rate of photosynthesis increases to an optimum then decreases. ### Light Intensity - Usually investigated by moving a plant closer to a light source and recording the O2 produced. - As light intensity increases so does the rate of photosynthesis until lack of another factor (e.g. CO2) limits any further increase. ### Carbon Dioxide - When investigating the effect of CO2 on photosynthesis, scientists enclose the leaf in a transparent bagjar with sodium hydroxide, this chemical absorbs CO2. - As CO2 increases the rate of photosynthesis increases until another factor limits the increases (e.g. light intensity). ## Testing a Leaf for Starch - Leaves kept in the dark for 24 hrs are destarched. - They can then be used to investigate photosynthesis in different conditions. - If a plant has been photosynthesising its leaf will contain starch. ### The Test: 1. Boil the leaf to kill it 2. Decolourise using ethanol 3. Wash to soften 4. Test with iodine - a blue/black colour shows the presence of starch. ## Minerals - Separate Science Only - Plants need certain minerals for healthy growth. - A deficiency of certain minerals cause specific growth problems. | Deficient Mineral | Growth Problem | |---|---| | Nitrates | Poor growth | | Potassium | Yellowing of leaf | | Phosphates | Poor root growth | ## Roots - The root hairs increase the surface area for absorption of water. - Minerals are actively transported into the cells which allows water to be drawn by osmosis into the root cells and then to the xylem. - The active transport means that root cells are actively respiring requiring lots of oxygen. ## 1.5 Plants and Photosynthesis - Answers 1. What is the equation for photosynthesis? Carbon dioxide + water → Glucose + Oxygen 2. What is the balanced symbol equation for photosynthesis? 6CO2 + 6H2O → C6H12O6 + 6O2 3. How can glucose be used in respiration? To release energy. 4. What is the function of chlorophyll in leaves? Absorbs light energy. 5. What is the by-product of photosynthesis?  Oxygen. 6. How can glucose aid structural support in plants? Glucose can be converted to cellulose that can be used to make plant cell walls. 7. Name three things that can increase the rate of photosynthesis. Higher carbon dioxide concentration, higher light intensity and higher temperature. 8. When do plants respire? All day and night. 9. What can algae and plants convert glucose into? Insoluble starch, fats or oils, cellulose, proteins (using nitrates).