Photosynthesis

• What is the word equation for photosynthesis?


  Carbon dioxide + water + sunlight -> glucose + oxygen
• Where does the energy for photosynthesis come from?


  Sunlight
• In which organ do most photosynthesis take place?


  Leaf
• In which organelle (sub-cellular structure) does photosynthesis take place?


  Chloroplast
• Which substance is responsible for absorbing the light energy for photosynthesis?


  Chlorophyll
• How do plants get the carbon dioxide required for photosynthesis?


  Diffuses from the air into the leaves via stomata
• How do plant get their water required for photosynthesis


  Diffuses from the soil into the root hair cells via osmosis
• Give 3 features of starch that make it a useful long-term storage molecule


  • Insoluble to water
  • Compact
  • Easily broken down when needed
• Is photosynthesis endothermic or exothermic?


  Endothermic - requires energy from the sun
• What is the symbol equation for photosynthesis?


  $6CO_2+$$6H_2O=$$C_6H_{12}O_6+$$6O_2$
• Give 5 ways plants can use glucose that they produce

  • Cellular respiration - break down glucose to release energy
  • Make cellulose - makes strong walls
  • Make starch - stores glucose
  • Make amino acids - makes proteins
  • Make lipids - store energy as fats or oils
• What are the 3 environmental factors that affect the rate of photosynthesis?


  • Temperature
  • Light intensity
  • Carbon dioxide concentration
• What is a limiting factor?


  Anything that constraints (limits) the rate of reaction
• How does the rate of photosynthesis vary with temperature?


  • Initially increases because particles have more energy and move faster and react more frequently
  • Highest rate occurs at optimum temperature for enzymes
  • Higher temperatures, rate decreases as bonds holding enzymes together begin txobreak, so enzymes change shape and are no longer complementary to the substrates
  • Rate falls to zero as enzymes denature
• Why do farmers use greenhouses?


  • Trap heat energy from sun and increase temperature
  • Keep out pests which could otherwise damage the plants
  • Make it easier to control the conditions, such as levels of carbon dioxide, fertiliser, water etc.
• What are paraffin heaters, and why are they used in greenhouses?


  • Burn a fossil fuels called paraffin
  • Produces carbon dioxide and heat energy, both help plants to grow
• What is the formula that links light intensity and distance?


  L is directly proportional to 1/d$^2$