To evaluate the claim that plants create everything they need to build all biomolecules through photosynthesis, we need to break down the components involved:
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Photosynthesis: This process allows plants to convert light energy, usually from the sun, into chemical energy in the form of glucose (sugar). The general equation for photosynthesis can be summarized as: \[ 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{light energy} \rightarrow \text{C}6\text{H}{12}\text{O}_6 + 6 \text{O}_2 \] This means that carbon dioxide (from the air) and water (from the soil) are converted into glucose and oxygen.
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Biomolecules: Animals and plants both require different types of biomolecules:
- Carbohydrates (like glucose)
- Proteins (which are made of amino acids)
- Lipids (fats, which include fatty acids)
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Cellular Respiration: This process allows plants to convert the glucose produced in photosynthesis into ATP (energy) by breaking it down in the presence of oxygen: \[ \text{C}6\text{H}{12}\text{O}_6 + 6 \text{O}_2 \rightarrow 6 \text{CO}_2 + 6 \text{H}_2\text{O} + \text{energy} \]
Now, regarding the statements:
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"This is not true because plants need to perform cellular respiration to break down the glucose into carbon, hydrogen, and oxygen." - While plants do perform cellular respiration, this statement does not directly address whether plants can create all necessary biomolecules from photosynthesis.
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"This is true because photosynthesis produces glucose, and plants only need sugars, not amino acids or fatty acids." - This is misleading because while glucose provides energy, plants also need other biomolecules (e.g., amino acids, fatty acids) for growth and structure.
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"This is not true because plants need to sequester nitrogen from the soil to build amino acids." - This is a valid statement. Plants require nitrogen to synthesize amino acids, which are essential for proteins. This indicates that photosynthesis alone is not sufficient for creating all biomolecules.
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"This is true because photosynthesis produces glucose, which has carbon, hydrogen and oxygen—the building blocks for all biomolecules." - This statement simplifies the process. While glucose does provide carbon, hydrogen, and oxygen, it does not address the need for nitrogen and other nutrients required to form amino acids and other biomolecules.
Conclusion: The correct interpretation is that plants cannot produce everything they need solely from photosynthesis. They require additional elements (e.g., nitrogen) from the soil to synthesize amino acids and other biomolecules. Therefore, the statement is not true. The most accurate response is: "This is not true because plants need to sequester nitrogen from the soil to build amino acids."