Topic 6 – Plant Structures and their Functions-Photosythesis Flashcards
What is photosynthesis?
A chemical reaction that takes place inside photosynthetic organisms (e.g. plants, algae) 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?
photosynthesis is important as it produces glucose which has a wide range of uses:
● It is 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 kinetic energy 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? (higher)
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) (higher)
● Using a light meter
● Using the inverse square law where:
light intensity is directly proportional to 1 over distance squared
Why does the rate of photosynthesis decrease as the distance from a light source increases? (higher)
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.
