Photosynthesis 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 (CHECK GOOGLE IF UNSURE)
Why is photosynthesis important?
It produces glucose which has a wide range of uses:
● 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 green 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?
Avariable 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
Draw a graph to show the effect of increasing
temperature on the rate of photosynthesis
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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
Draw a graph to show the effect of light
intensity on the rate of photosynthesis
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How can the effect of light intensity on the rate of
photosynthesis be measured in the lab?
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.
Explain how carbon dioxide concentration affects the
rate of photosynthesis
As carbon dioxide concentration increases,
the rate of photosynthesis increases
Why does the rate of photosynthesis eventually
plateau even if CO2
concentration continues to
increase?
Another factor (temperature or light intensity) becomes limiting.
Draw a graph to show the effect of carbon dioxide
concentration on the rate of photosynthesis
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Which two organisms do photosynthesis?
Plants and Algae
Where is the energy of a plant stored?
In the glucose formed through photosynthesis.
Define biomass
The total mass of an organism (this is produced by plants and algae through photosynthesis)
What is a polymer of glucose called formed during photosynthesis?
Starch
What happens to the starch after photosynthesis stops?
They made into simpler substances, which are moved into the cytoplasm and used to make sucrose.
What is the purpose of sucrose?
Transported around the plant and used to make:
- starch (in a storage organ such as a potato)
- other molecules for the plant (such as cellulose, lipids or proteins)
- glucose for respiration
