photosynthesis (required practical) Flashcards
what is photosynthesis?
using energy from the sun to convert carbon dioxide and water into glucose and oxygen.
what is the formula for photosynthesis?
carbon dioxide + water → glucose + oxygen (6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂)
what are the 5 ways plants use glucose?
- respiration.
- making cellulose. (to make cell walls)
- making amino acids. (combined with nitrate ions)
- stored as oils or fats. (stored in seeds)
- stored as starch. (stored in roots stems leaves for when photosynthesis isn’t happening)
what 4 things affect the rate of photosynthesis?
light intensity.
CO₂ concentration.
temperature.
chlorophyll amount. (can be reduce by disease)
(the limiting factor is the one that stops photosynthesis from happening any faster)
how does light carbon dioxide and temperature affect the rate of photosynthesis?
light provides energy needed for photosynthesis. (as the light level is raises the rate increases steadily to a certain point)
CO₂ is one of the materials needed for photosynthesis.
enzymes needed for photosynthesis work more slowly at low temperatures but if they are too hot they are damaged. (at ~45°c)
how can the effect of light on the rate of photosynthesis be measured? (practical)
pondweed can be used to measure the effect of light intensity by the rate it produces oxygen.
1. cut an 8cm piece of pondweed and put it in a boiling tube of water.
2. place the tube a set distance from the light.
3. connect a gas syringe to the tube.
4. leave the weed to photosynthesise for a set amount of time.
5. measure the length of the air bubble in the gas syringe. (repeat the test 3 times to get a mean oxygen amount.
6. repeat the test at a different distance from the light source.
what is the inverse square law?
light intensity decreases in proportion to the square of the distance.
what is the formula for the inverse square law?
light intensity ∝ 1 ÷ distance²
