Photosynthesis: energy enters through light
| English | 中文 | Pinyin |
|---|---|---|
| chlorophyll/ˌklɔːrəʊˈfɪl/ | 叶绿素 | yè lǜ sù |
| endothermic/ˌendəʊˈθɜːmɪk/ | 吸热的 | xī rè de |
What would explain this observation?
- A growing plant gains material without eating another organism. It uses carbon dioxide and water to make glucose, with energy transferred by light.
- Start with a prediction. State the quantities or features you would compare, then decide what evidence could distinguish two explanations.
Build the model
- Photosynthesis is represented by carbon dioxide + water → glucose + oxygen, in the presence of light. Carbon dioxide is CO₂, water is H₂O, glucose is C₆H₁₂O₆ and oxygen is O₂. Chloroplasts contain chlorophyll 叶绿素, which absorbs light. The reaction is endothermic 吸热的: energy is transferred from the environment to the chloroplasts by light.
- chlorophyll: A pigment that absorbs light for photosynthesis; endothermic: Describing a reaction that takes in energy from its surroundings.
What is the role of light in the photosynthesis equation?
Light supplies energy rather than being a material reactant with a mass in the equation. Carbon dioxide supplies carbon for glucose; water is also required and oxygen is released. Photosynthesis and respiration are different processes. Plants respire continuously in living cells, even when no light is available for photosynthesis.
Match each technical term to its precise meaning.
Use the definitions to distinguish related quantities and processes.
Choose evidence that can test it
- Light supplies energy rather than being a material reactant with a mass in the equation. Carbon dioxide supplies carbon for glucose; water is also required and oxygen is released. Photosynthesis and respiration are different processes. Plants respire continuously in living cells, even when no light is available for photosynthesis.
- Use a labelled chloroplast model and equation cards to identify reactants, products and the energy input. If using the balanced extension 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, count atoms to check conservation. Recognizing the required symbols does not require an invented mole calculation or an ATP yield.
Which two habits make the investigation or model in this case more defensible?
Use a labelled chloroplast model and equation cards to identify reactants, products and the energy input. If using the balanced extension 6CO₂ + 6H₂O → C₆H₁₂O₆ + 6O₂, count atoms to check conservation. Recognizing the required symbols does not require an invented mole calculation or an ATP yield.
Work from known quantities
- State the known values and their units. Choose the relation because its assumptions fit this case, then rearrange before substitution.
- Known: the balanced model uses 6 carbon dioxide molecules for one glucose molecule. For 4 glucose molecules the model requires 24 carbon dioxide molecules and produces 24 oxygen molecules. This is a particle-ratio check of the equation, not a measurement of a real leaf’s rate or a statement that light has six molecules.
In the supplied balanced model, 6 carbon dioxide molecules are used per glucose. How many are used for 3 glucose molecules? Use the same sequence: known quantities → model → relation → substitution → unit and interpretation.
In the supplied balanced model, 6 carbon dioxide molecules are used per glucose. How many are used for 3 glucose molecules?
The result is 18 molecules. Known: the balanced model uses 6 carbon dioxide molecules for one glucose molecule. For 4 glucose molecules the model requires 24 carbon dioxide molecules and produces 24 oxygen molecules. This is a particle-ratio check of the equation, not a measurement of a real leaf’s rate or a statement that light has six molecules.
Check the conclusion and its limits
- Photosynthesis takes in energy; it does not release usable energy from glucose in the way respiration does. Chlorophyll and chloroplast are not interchangeable: one is the light-absorbing pigment, the other the cell structure containing it.
- Return to the original observation. Explain what the result supports, which conditions it assumes, and one way to test a competing explanation.
Plants stop respiring whenever they photosynthesize. This claim is false: Photosynthesis takes in energy; it does not release usable energy from glucose in the way respiration does. Chlorophyll and chloroplast are not interchangeable: one is the light-absorbing pigment, the other the cell structure containing it.
Photosynthesis: energy enters through light: Light supplies energy rather than being a material reactant with a mass in the equation. Carbon dioxide supplies carbon for glucose; water is also required and oxygen is released. Photosynthesis and respiration are different processes. Plants respire continuously in living cells, even when no light is available for photosynthesis.
Plants stop respiring whenever they photosynthesize.
Photosynthesis takes in energy; it does not release usable energy from glucose in the way respiration does. Chlorophyll and chloroplast are not interchangeable: one is the light-absorbing pigment, the other the cell structure containing it.
A pigment that absorbs light for photosynthesis: write the technical term.
chlorophyll means A pigment that absorbs light for photosynthesis.