Photosythesis

• Photosynthesis


  Carbon Dioxide + Water Glucose + Oxygen
• Photosynthesis


  An endothermic reaction in which energy is transferred from the environment to the chloroplasts by light
• Chloroplasts


  • Cell structure where photosynthesis takes place
  • Contain chlorophyll, a green pigment needed for photosynthesis
• Palisade cells


  • Packed closely together and contains lots of chloroplasts to maximise photosynthesis
• Spongy mesophyll cells


  • Have lots of spaces for oxygen and carbon dioxide to be able to diffuse through easily
• Xylem


  • Transports water needed for photosynthesis to the leaf
• Phloem


  • Transports sugars made during photosynthesis to the rest of the plant
• Guard cells


  • Open and close the stoma to let carbon dioxide in and oxygen and water out
• Stoma


  • A pore. Carbon dioxide needed for photosynthesis enters the leaf here. Oxygen made during photosynthesis is able to leave the leaf here
• Chlorophyll


  The chemical that makes a leaf look green
• The yellow region of the leaf had not produced sugar because it does not contain chlorophyll, which is needed to absorb light
• Sunlight/Light


  The source of energy that leaves need to make food
• Chloroplast


  The part of the plant cell where photosynthesis takes place
• Palisade cells


  • It has lots of chloroplasts for photosynthesis
• Guard cells


  • Control size of stoma
• Sunlight


  Necessary for photosynthesis as plants need energy to make glucose
• Chloroplasts


  Where plants get the energy for photosynthesis by trapping light
• Photosynthesis


  An endothermic reaction
• Boiling tube A


  The control to check that the indicator colour doesn't change on its own
• Boiling tube E


  The indicator would be the most yellow after 2 days as it has the most carbon dioxide with no carbon dioxide used for photosynthesis
• Temperature


  • As temperature increases the rate of photosynthesis increases up to around 35-40°C
  • Beyond the optimum temperature the rate of photosynthesis will decrease as the enzymes involved have been denatured
  • At around 45°C photosynthesis will stop completely as all the enzymes have been denatured
• Light Intensity


  • As the light level is raised the rate of photosynthesis increases also up to a point
  • Beyond this point, the rate of photosynthesis will increase no further as either the temperature or carbon dioxide level have become a limiting factor
• Carbon Dioxide Concentration


  • As the levels of carbon dioxide increases the rate of photosynthesis increase also up to a point
  • Beyond this point, the rate of photosynthesis will increase no further as either the temperature or light intensity have become a limiting factor
• In bright sunlight, the concentration of carbon dioxide in the air can limit the rate of photosynthesis
• Decreasing water availability


  Decreases the rate of photosynthesis
• More light


  More photosynthesis, up to a limit
• More CO2


  More photosynthesis
• High temp


  Increases rate of photosynthesis
• Investigating effect of light on rate of photosynthesis

  Set up equipment as shown

  2. Place pondweed 10cm from light

  3. Turn on light and leave 5 mins to acclimatise

  4. Count bubbles in 1 minute

  5. Repeat at 20, 30, 40 and 50cm

  6. Repeat to identify outliers and calculate averages
• Control Variables


  • Size of pondweed

  Type of pondweed

  Colour of light

  Temperature of water

  Time for plant to equilibrate

  Carbon dioxide concentration

  Volume of water in beaker
• Doing 3 repeats allows identification of outliers which can then be discarded when calculating averages
• Investigating effect of light intensity on rate of photosynthesis

  Place pondweed in beaker of water

  2. Shine light on beaker

  3. Leave for 5 minutes to acclimatise

  4. Place bulb 10cm away from pondweed

  5. Count bubbles in a minute

  6. Repeat at 20, 30, 40 and 50cm

  7. Do 3 repeats

  8. Identify outliers and discard from averages

  9. State a control variable and describe how it is controlled
• Uses of Glucose


  • Respiration

  Making insoluble starch for storage

  Making fats or oils for storage

  Making cellulose

  Making amino acids for protein synthesis
• Making starch from carbon dioxide

  Carbon dioxide enters through stomata

  Glucose produced by photosynthesis

  Sugars transported by translocation in phloem

  Glucose is converted into starch

  Starch is a long chain of glucose

  Starch is stored
• The presence of starch shows that photosynthesis has taken place
• Respiration


  An exothermic reaction which is continuously occurring in living cells, transferring energy needed for living processes
• What we need energy for

  • Movement

  Keeping Warm

  Chemical reactions to build larger molecules
• Aerobic Respiration


  Glucose + Oxygen Carbon Dioxide + Water
• Anaerobic Respiration in muscles

  Glucose Lactic Acid
• Anaerobic Respiration in yeast and plant cells


  Glucose Ethanol + Carbon Dioxide