4.1 Photosynthesis Flashcards
What is photosynthesis?
The process by 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)
carbon dioxide + water –> glucose + oxygen
6CO2 + 6H2O –> C6H12O6 + 6O2
Is photosynthesis an exothermic or endothermic reaction, and why?
Endothermic - energy is transferred from the environment to chloroplasts by light.
How can you show that a plant gives off oxygen during photosynthesis?
Using a water plant (e.g. Elodea), collect gas bubbles produced during photosynthesis . The gas will relight a glowing splint as it contains oxygen.
Give examples of leaf adaptations which maximise the rate of photosynthesis
● Broad leaves - maximise surface area
● Thin leaves - short diffusion distance
● Chlorophyll present - to 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 the opening of stomata for 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 (e.g. due to a lack of 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 e.g. light intensity
Explain how you can calculate the rate of photosynthesis by measuring oxygen production
- Set up bubble potometer apparatus (pondweed in a
sealed tube of water, attached to a capillary tube and gas syringe) - Oxygen gas produced causes the bubble in the capillary tube to move. The distance moved by the bubble is used to calculate the volume of oxygen
produced - The higher the volume of oxygen produced, the
higher the rate of
photosynthesis
How can farmers use their knowledge of limiting factors to increase their profits? (Higher)
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. (Higher)
Inverse square law
Light intensity is inversely proportional to 1/distance^2
