Topic 4-Bioenergetics Flashcards
Where does photosynthesis take place
In the chloroplasts in green plant cells. They contain pigments like chlorophyll which absorb light
How is energy transferred to the chloroplasts from the environment
By light
Is photosynthesis endothermic or exothermic
Endothermic
This means that energy is transferred from the environment in the process
Word equation for photosynthesis
Carbon dioxide + water —-> (light) glucose + oxygen
Symbol equation for photosynthesis
6CO2 + 6H2O ——> (light) C6H12O6 + 6O2
Plants use glucose in 5 main ways
•For respiration
This transfers energy from glucose which enables the plants to convert the rest of the glucose into various other useful substances
Plants use glucose in 5 main ways
•Making cellulose
Glucose is converted into cellulose for making strong plant cell walls
Plants use glucose in 5 main ways
•Making amino acids
Glucose is combined with nitrate ions (absorbed from the soil) to make amino acids, which are then made into proteins
Plants use glucose in 5 main ways
•Stored as oils or fats
Glucose is turned into lipids (fats and oils) for storing in seeds
Plants use glucose in 5 main ways
•Stored as starch
Glucose is turned into starch and stored in roots, stems and leaves, ready for use when photosynthesis isnt happening, like in winter. Starch is insoluble which makes it much better for storing than glucose-a cell with lots of glucose in would draw in loads of water and swell up
The limiting factors that affect rate of photosynthesis are
- light
- temperature
- amount of carbon dioxide
- amount of chlorophyll
Effects of light on rate of photosynthesis
Light provides the energy needed for photosynthesis.
As the light level is raised, the rate of photosynthesis increases steadily but ot up to a certain point (the optimum).
Beyond that, light wont make any difference because it will be either co2 or temperature that is the limiting factor
Effects of carbon dioxide levels on rate of photosynthesis
CO2 is one of the raw materials needed for photosynthesis.
The amount of CO2 will only increase the rate of photosynthesis up to a certain point (the optimum). After this CO2 is no longer a limiting factor
Effects of temperature on rate of photosynthesis
Temperature affects the rate of photosynthesis because it affects the enzymes involved
Usually if temp is the limiting factor its because it is too low (enzymes work slower at low temps). But if the plant gets too hot the enzymes will be damaged. This happens at about 45 degrees
Required practical:
Oxygen production shows the rate of photosynthesis
(The pondweed one)
- Source of light placed specific distance from pondweed
- Pondweed is left to photosynthesise for a set length of time. Oxygen produced will collect in capillary tube
- At the end, use syringe to draw gas bubbles up tube along a ruler and measure length of bubble. This is proportional to volume of O2 produced
Required practical:
Oxygen production slows the rate of photosynthesis
(The pondweed one)
PART 2
- Variables should be controller e.g temperature and time to photosynthesise
- Repeat twice with light at same distance and calculate a mean
- Repeat whole experiment with light source at different distances from pondweed
The inverse square law links light intensity and distance
EQUATION
Light intensity (is proportional to/fish thing) 1
——
Distance squared