Photosynthesis Flashcards
What is photosynthesis?
The process to which plants synthesise glucose using light energy from the Sun. Light energy is converted into chemical energy.
Where does photosynthesis take place?
Within chloroplasts in leaf palisade cells. They contain chlorophyll, a pigment which absorbs light energy.
State the equations for photosynthesis (word and symbol)
Word : carbon dioxide + water –> glucose + oxygen
Symbol : 6CO2 + 6H2O –> C6H12O6 + 6O2
Include light above the arrows.
Is photosynthesis an endothermic or exothermic reaction, and why?
Endothermic - energy is transferred from the environment to chloroplasts by light.
How can you that a plant gives off oxygen during photosynthesis?
Using a water plant such as elodea, collect gas bubbles produced during photosynthesis. The gas will relight a glowing splint as it contains oxygen.
Give examples of leaf adaptation which maximise the rate of photosynthesis
- Blood vessels and broad leaves: maximise surface area.
- Thin leaves: short diffusion distance.
- Chlorophyll present: trap light energy.
- Veins: transport water to leaves via xylem, remove photosynthesis products via phloem.
- Air spaces: allow CO2 to enter and O2 to leave.
- Guard cells: control opening and closing of stomata to gaseous exchange and prevent water loss.
What are the four main factors that affect the rate of photosynthesis?
- Temperature.
- Light intensity.
- Carbon dioxide concentration.
- Amount of chlorophyll.
How does temperature affect the rate of photosynthesis?
Increasing the temperature increases the rate of photosynthesis as the kinetic energy of particles is increased. The rate decreases past a certain temperature as enzymes become denatured.
How does light intensity affect the rate of photosynthesis?
Increasing the light intensity increases the rate of photosynthesis until another factor becomes limiting.
How does carbon dioxide concentration affect the rate of photosynthesis?
Increasing the carbon dioxide concentration increases the rate of photosynthesis (until another factor becomes limiting) as CO2 is required to make glucose.
How does the amount of chlorophyll affect the rate of photosynthesis?
Decreasing the amount of chlorophyll (due to a lack magnesium) decreases the rate of photosynthesis as chlorophyll is required to absorb light energy.
What is a limiting factor?
An environmental factor which can restrict the rate of photosynthesis such as light intensity.
How can farmers use their knowledge of limiting factors to increase their profits?
They can control temperature, light intensity and CO2 concentration to achieve the fastest possible rate of photosynthesis, leading to a greater yield.
State the law which describes the relationship between the distance of a light source from a plant and light intensity
It is known as inverse square law.
Light intensity is proportional to 1/distance^2
State the 5 uses of glucose produced during photosynthesis
- Respiration.
- Starch for storage.
- Cellulose for strength.
- Amino acid and protein synthesis (combined with nitrates).
- Lipids for energy storage in seeds.
