Why vitamins are required in the diet — best general statement about biosynthetic capacity and quantitative need in humans.
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AOrganisms cannot synthesize these compounds at all
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BOrganisms can synthesize these compounds only partially
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COrganisms cannot synthesize these compounds in adequate amounts to meet physiological demand
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DNone of the above
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EThey are needed only during illness, not health
Answer
Correct Answer: Organisms cannot synthesize these compounds in adequate amounts to meet physiological demand
Explanation
Introduction / Context:Vitamins are organic micronutrients required in small amounts for normal metabolism. The core reason they must be supplied by diet varies by vitamin and organism.
Given Data / Assumptions:
- Some vitamins cannot be synthesized at all by humans (e.g., vitamin C), others are synthesized insufficiently (e.g., niacin from tryptophan in limited amounts).
- Physiological demand exceeds endogenous production for many vitamins.
Concept / Approach:The most accurate generalization is that endogenous synthesis is absent or inadequate for meeting needs; therefore, dietary intake is essential.
Step-by-Step Solution:Evaluate absolute vs limited synthesis scenarios across vitamins.Recognize “inadequate amounts” captures both none and insufficient production cases.Select the statement that encompasses all vitamins broadly.Choose option c.
Verification / Alternative check:Nutrition guidelines recommend dietary intake despite partial synthesis for certain vitamins (e.g., niacin, vitamin D via skin under sunlight) due to variability and insufficiency.
Why Other Options Are Wrong:“Cannot synthesize at all” is too absolute; “partial synthesis” is too narrow; “none of the above” is incorrect; health-only need is false.
Common Pitfalls:Overgeneralizing from a single vitamin to all vitamins.
Final Answer:Organisms cannot synthesize these compounds in adequate amounts to meet physiological demand.