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IB Biology C1.3: Photosynthesis — Practice Questions & Answers
IB Biology C1.3 Photosynthesis study notes: light absorption by pigments, conversion of light energy to chemical energy, limiting factors and measurement.
Here are 10 practice questions with full answers and explanations.
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Practice questions with answers
1
Multiple choice
What energy transformation occurs during photosynthesis?
Light energy to chemical energy.
Chemical energy to light energy.
Thermal energy to chemical energy.
Kinetic energy to chemical energy.
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Why Photosynthesis converts light energy into chemical energy stored in glucose.
2
Multiple choice
What is converted to glucose during photosynthesis?
Carbon dioxide.
Oxygen.
Nitrogen.
Water.
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Why Carbon dioxide is fixed and reduced during the Calvin cycle to form glucose.
3
Multiple choice
What is the source of hydrogen used to convert carbon dioxide to glucose?
Splitting of water.
Atmospheric hydrogen.
Carbon dioxide breakdown.
Glucose breakdown.
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Why Photolysis splits water, supplying the hydrogen (as reduced NADP) used to reduce carbon dioxide.
4
Multiple choice
What is a by-product of photosynthesis in plants, algae, and cyanobacteria?
Oxygen.
Carbon dioxide.
Water.
Nitrogen.
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Why Oxygen is released as a by-product when water is split during the light-dependent reactions.
5
Multiple choice
What technique is used to separate and identify photosynthetic pigments?
Chromatography.
Electrophoresis.
Centrifugation.
Spectrophotometry.
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Why Chromatography separates pigments by their differing solubility and movement, allowing identification.
6
Multiple choice
What is the Rf value in chromatography?
The ratio of the distance traveled by the sample to the distance traveled by the solvent
The ratio of the distance traveled by the solvent front to the distance traveled by the sample
The distance traveled by the sample
The distance traveled by the solvent front
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Why The Rf value is the distance moved by the pigment divided by the distance moved by the solvent.
7
Multiple choice
What happens to electrons within a pigment molecule when light is absorbed?
They are excited.
They are lost.
They are stabilized.
They are transferred to carbon dioxide.
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Why Absorbed light raises electrons in the pigment to a higher, excited energy state.
8
Multiple choice
What is an absorption spectrum?
A graph showing the wavelengths of light absorbed by a pigment.
A graph showing the rate of photosynthesis.
A graph showing the concentration of carbon dioxide.
A graph showing the temperature effects on photosynthesis.
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Why An absorption spectrum plots how much light of each wavelength a pigment absorbs.
9
Multiple choice
What is an action spectrum?
A graph showing the rate of photosynthesis at different wavelengths of light.
A graph showing the absorption of light by a pigment.
A graph showing the rate of respiration.
A graph showing the concentration of oxygen.
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Why An action spectrum plots the rate of photosynthesis against wavelength of light.
10
Multiple choice
What are limiting factors in photosynthesis?
Factors that restrict the rate of photosynthesis.
Factors that increase the rate of photosynthesis.
Factors that have no effect on photosynthesis.
Factors that denature enzymes.
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Why Limiting factors are conditions, such as light or CO₂, that cap the rate of photosynthesis.
Key terms in Photosynthesis
Photosynthesis: The conversion of light energy into chemical energy stored in carbohydrates, producing oxygen as a by-product.
Chlorophyll: The main photosynthetic pigment, which absorbs red and blue light strongly and reflects green light.
Pigment: A coloured molecule that absorbs certain wavelengths of light; in photosynthesis it captures the energy that drives the process.
Absorption spectrum: A graph of how much light of each wavelength a pigment absorbs.
Action spectrum: A graph of the rate of photosynthesis achieved at each wavelength of light.
Limiting factor: The environmental factor in shortest supply that currently controls the rate of a process such as photosynthesis.
Photolysis: The splitting of water molecules using light energy, which releases the oxygen given off in photosynthesis.
Endothermic: Describing a reaction that absorbs energy; photosynthesis stores light energy as chemical energy in its products.
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