Chp - 6 photosynthesis

• Nutrition

  Taking in useful substances
• Organic substances


  • Proteins
  • Fats
  • Carbohydrates
  • DNA
• Animals


  Cannot make organic substances, take them in as nutrients when they feed
• Plants


  Make organic substances using inorganic substances (carbon dioxide, water, mineral ions)
• Photosynthesis


  Making with light
• Chlorophyll


  Pigment in chloroplasts that absorbs light energy
• Chloroplasts


  • Little packets that contain chlorophyll and transfer light energy to molecules to make glucose
• Photosynthesis


  Carbon dioxide + water + light energy -> Glucose + oxygen
• Nitrates


  Useable source of nitrogen to make amino acids
• Amino acids

  Make proteins which are needed for growth
• Magnesium ions


  Needed for chlorophyll
• Chlorophyll deficiency


  Plants cannot absorb sunlight, so cannot photosynthesize, leading to less growth and sugar production
• Upper epidermis


  • Thin and transparent to allow light to pass through to palisade mesophyll
• Palisade mesophyll cells


  • Packed tightly together near the upper surface to maximize light absorption
  • Contain many chloroplasts
• Spongy mesophyll

  • Large intercellular air spaces to allow easy diffusion of carbon dioxide
• Lower epidermis


  • Contains stomata to allow diffusion of carbon dioxide and oxygen
• Stomata


  Allow gas exchange and diffusion of carbon dioxide, oxygen, and water vapour
• Chloroplasts

  • Found in palisade mesophyll, spongy mesophyll, and guard cells where photosynthesis occurs
• Xylem in veins bring water and ions to the mesophyll cells, which are needed for photosynthesis
• Phloem in veins transport the sugar produced in photosynthesis away from the leaf
• Vascular bundles


  • Collections of xylem and phloem vessels in the veins of leaves
• Factors affecting photosynthesis


  • Quantity of sunlight
  • Temperature
  • Supply of new materials (CO2 and H2O)
• Carbon dioxide indicators can be used to test for photosynthesis
• Investigating necessity of carbon dioxide for photosynthesis


  1. Use potassium hydroxide to absorb CO2

  2. Use sodium hydrogen carbonate to produce CO2
• Starch test

  1. Boil leaves to break down cell membranes

  2. Add iodine solution to test for presence of starch
• Variegated leaves show blue-black starch in green parts and brown in white parts
• Leaves are put in a cupboard to destarched by using up their starch stores
• Investigating effect of light intensity on photosynthesis rate

  1. Use aquatic plant

  2. Vary CO2 by adding sodium hydrogen carbonate

  3. Vary temperature by using water bath
• Limiting factors

  Sunlight, water, carbon dioxide