B8 - Photosynthesis Flashcards
Give the equation for photosynthesis and its energy change:
endothermic (energy transfer from environment to chloroplasts by light)
State 4 factors that affect the rate of PS:
Don’t describe any of them
-temperature
-light intensity
-CO₂ concentration
-amount of chlorophyll (differs between different plants)
Remember this is different to the factors affecting rate of transpiration, so don’t say humidity or wind
How does temperature affect the rate of PS? Give the graph that displays this information:
-enzymes catalyse PS
-increasing temp. makes it optimum temperature until increasing it further denatures them
How does light intensity affect the rate of PS? Give the graph that displays this information:
-more light, more energy for PS
-plateaus usually due to other limiting factors
-remember light intensity is affected by the inverse square law
How does CO₂ concentration affect the rate of PS? Give the graph that displays this information:
-CO₂ is a reactant in PS
-more of it means more PS can occur
Why are limiting factors important to farmers?
it is important to enhance conditions within greenhouses to maximise rate of PS whilst also maintaining max. profit
RP6 - How would you investigate the effect of light intensity on the rate of photosynthesis?
-put boiling tube in a rack with sodium hydrogen carbonate solution in it, and place a section of pondweed inside it
-place an LED light 10cm away from the tube, and allow it to rest for 5 minutes
-start stopwatch and count #bubbles produced in 1 minute
-do 1/d² for light intensity, and record bubble rate with it
-repeat but move light away at least 5 times (20, 30, 40, 50)
-plot bubbles per minute vs LI
RP6 - How could you make the results of the rate of photosynthesis experiment more valid?
-repeat and calculate mean
-control water temperature
-control carbon dioxide concentration
-control mass/type of pondweed
RP6 - Why is sodium hydrogen carbonate solution used for the pondweed?
it releases CO₂ which is used by the pondweed for PS
RP6 - Why can we use the number of bubbles as a way to measure rate of PS? Why might it be inaccurate, and how could it be improved?
-oxygen gas is produced as a product in PS
-bubbles can be of different sizes, a more accurate method would be to measure volume and use a delivery tube and collect the oxygen over water in a measuring cylinder
What is glucose used for in a plant?
-starch (compact storage method)
-cellulose (strengthens cell walls)
-amino acids production for protein synthesis
-respiration
-fats/oils (storage, or for seeds)
(SCARF)
The fats are often used in seeds as they initially can’t photosynthesise (they are underground), so they use the lipids to respire
Why is glucose stored as starch in plants?
starch is compact and insoluble and won’t affect water concentrations inside cells
How do plants synthesise proteins?
nitrate ions from the soil are combined with glucose to make amino acids, and then they are used to synthesise proteins in the ribosome
What happens to chlorophyll when it lacks being exposed to light?
-breaks down
-leaves turn orange/yellow
This is why leaves turn orange/yellow in Autumn - the Sun is lower in the sky, so it gets less light
Why might a tree die if their roots are damaged?
-less absorption of water, less PS, so less glucose produced
-less absorption of nitrate ions for proteins for growth, and magnesium for chlorophyll
-damage to phloem/xylem (less transport of water/ions/sugars)
