Topic 6 Plant Structures and their Functions Flashcards
what is photosynthesis?
The chemical reaction that takes place in photosynthetic organisms converting light energy into chemical energy.
write the word equation for photosynthesis
carbon dioxide + water → glucose + oxygen
Write the symbol equation for photosynthesis
6CO2 + 6H2O → C6H12O6 + 6O2
Why is photosynthesis important?
● Used in respiration to release energy
● Converted to starch and stored - broken down to glucose when the
plant requires energy
● Used to make complex organic molecules which are used for growth,
making up an organism’s biomass (transferred through food chains)
Where does photosynthesis take place?
Within chloroplasts
What type of reaction is photosynthesis?
An endothermic reaction that takes in
energy (in the form of light)
What is chlorophyll?
A pigment found in chloroplasts that
absorbs light
Describe the two main stages of photosynthesis
- Chlorophyll absorbs light energy which is used to split
water into oxygen gas (waste product) and hydrogen ions - Carbon dioxide combines with hydrogen ions to form
glucose
What factors affect the rate of photosynthesis?
● Temperature
● Light intensity
● Carbon dioxide concentration
What is a limiting factor?
A variable that limits the rate of a
particular reaction
Explain how temperature affects the rate of
photosynthesis
● Higher temperatures provide more KE for enzymes involved in
photosynthesis so the rate increases as temperature rises
● The optimum temperature is usually 25°C
● If the temperature becomes too high (around 45°C) enzymes
become denatured and the rate of photosynthesis decreases
Explain how light intensity affects the rate of
photosynthesis
Rate of photosynthesis is directly proportional to
light intensity ∴ as light intensity increases, the
rate of photosynthesis increases.
Why does the rate of photosynthesis eventually
plateau even if light intensity continues to increase?
Another factor (temperature or CO2 concentration) becomes limiting.
How can the effect of light intensity on the rate of
photosynthesis be measured in the lab? (2)
● Using a light meter
● Using the inverse square law where:
Light Intensity = 1
——————-
(distance)2
Why does the rate of photosynthesis decrease as
the distance from a light source increases?
Light intensity is inversely proportional to the square
of the distance from the light source. Thus, as the
distance increases, light intensity decreases and the
rate of photosynthesis decreases.
