Photosynthesis

• What is the chemical equation for photosynthesis?


  6C02 + 6H20 > C6H12O6 + 6O2
• What are the leaf adaptations for photosynthesis? (6)


  1) Broad giving them a big surface area

  2) Thin so diffusion distance is short

  3) Chlorophyll

  4) Veins bringing in plenty of water from xylem

  5) Air spaces allowing CO2 to get into cells and O2 out

  6) Guard cells to open and close stomata to regulate gas exchange
• How are algae adapted to photosynthesis?


  They absorb the CO2 dissolved in the water around them
• What are the factors affecting photosynthesis? (4)


  1) Chlorophyll levels

  2) Light

  3) Temperature (*enzymes involved eventually denature if the temp gets too high which is why the rate begins to decrease again)

  4) CO2 concentration
• What are the steps of the light intensity practical? (7)


  1) Fill boiling tube with 35cm³ of sodium hydrogen carbonate solution as it releases C02 which is a reactant for photosynthesis

  2) Select pondweed leaving the cut end at the top

  3) Place boiling tube 10cm away from LED as LEDs don't produce that much light which is a factor affecting photosynthesis and if a normal light bulb is used then the boiling tube needs to be put in a beaker of water

  4) Leave the boiling tube to acclimatise for 5 minutes

  5) Start stopwatch and count the number of bubbles produced in 1 minute.

  6) Repeat 2x to find the mean

  7) Repeat steps 1-6 but instead increase the distance in intervals of 5
• What are the problems of the light intensity practical? (2)


  1) Number of bubbles may be too fast to count

  2) Bubbles aren't always the same size
• How do you solve the problems of the light intensity practical?


  Measure the volume of oxygen produced using a gas syringe
• What is the inverse square law?


  Doubling the distance between the lamp and pondweed causes the number of bubbles to fall by 4 times
• How is glucose used in plants? (5)


  1) Respiration

  2) Glucose is built into complex carbohydrates e.g., cellulose used to strengthen the cell wall

  3) Converted into starch

  4) Proteins

  5) Making lipids
• How can plants store large volumes of starch in their cells?


  Starch is insoluble in water so it has no effect of the water balance on the cell
• What is starch used for in plants?


  It provides an energy store for when it is dark
• How are amino acids made in plants?


  Glucose combines with nitrate and other mineral ions from the soil
• How are lipids made in plants and how are they used?


  Glucose and energy from respiration build up fats and oils used in cells as energy stores and sometimes to make the cell walls stronger
• What are the benefits of greenhouse economics? (3)


  1) Less staff needed

  2) Time from seed to harvest is much shorter

  3) Final crop is larger and cleaner