B4 - Bioenergetics Flashcards
What is photosynthesis?
The use of energy to change carbon dioxide and water into glucose and oxygen
Where does photosynthesis take place?
Chloroplasts in green plant cells - they contain pigments like chlorophyll that absorb light
What transfers energy to the chloroplasts?
Light
Photosynthesis is endothermic - what does this mean?
This means energy is transferred from the environment in the process
What is the word equation for photosynthesis?
carbon dioxide + water (light)> glucose + oxygen
What is the symbol equation for photosynthesis?
6CO2 + 6H2O (light)> C6H12O6 + 6O2
What are the main ways plants use glucose?
- Respiration
- Making cellulose
- Making amino acids
- Stored as oils or fats
- Stored as as starch
What is cellulose?
For making strong plant wall cells
How are amino acids formed?
Nitrate ions (from the soil) and glucose combine to form amino acids (which then turn into proteins)
How does a plant use fat or oil?
Storing in seeds
How does a plant use starch?
Used for when photosynthesis isn’t happening (winter) and because it is insoluble, it is much better for storing than glucose, so it stop the plant from swelling
What are the limiting factors that affect the rate of photosynthesis?
- Light
- Concentration of CO2
- Temperature
Give examples where the rate of photosynthesis could be affected
- Night
- Winter
- Warmth
What else can be considered a limiting factor?
Chlorophyll which can be affected by disease or environmental stress (lack of nutrients)
How does light intensity affect the rate of photosynthesis?
As the light level is raised, the rate of photosynthesis increases steadily, but only up to a certain point. Beyond that it won’t make any difference because it’ll either be the temperature or CO2 level which is now the limiting factor
How does carbon dioxide affect the rate of photosynthesis?
Similarly to light intensity, as the amount of CO2 increases, the rate of photosynthesis steadily increases as well to a certain point. Beyond that, it won’t make a difference so as long as a plant has plenty of CO2 and light, temperature should be the limiting factor.
How does temperature affect the rate of photosynthesis?
Enzymes work faster with more heat (usually most efficient around 37) but if they get too hot, then they can become denatured (usually happens around 45)