Rucete ✏ Campbell Biology In a Nutshell
Unit 7 ANIMAL FORM AND FUNCTION — Concept 41.1 An Animal’s Diet Must Supply Chemical Energy, Organic Building Blocks, and Essential Nutrients
What Makes a Nutrient “Essential”?
- Essential nutrients are substances animals cannot synthesize and must obtain from food.
- Four classes:
- Amino acids
- Fatty acids
- Vitamins
- Minerals
These are needed in small amounts but are vital for metabolism, structure, and function.
1. Essential Amino Acids
- Animals need 20 amino acids, but many can only make about half.
- The rest (essential amino acids) must come from diet.
- Plant-based foods often lack one or more, so vegetarians need complementary sources (e.g., rice + beans).
2. Essential Fatty Acids
- Some unsaturated fatty acids (e.g., linoleic acid) are essential.
- Used in:
- Membrane phospholipids
- Signaling molecules like prostaglandins
- Deficiencies are rare in diets with seeds, grains, or vegetables.
3. Vitamins
- Organic molecules needed in tiny amounts (0.01–100 mg/day)
- Two types:
- Water-soluble: B-complex, C
- Fat-soluble: A, D, E, K
- Function mainly as coenzymes
- Fat-soluble ones can accumulate and become toxic
4. Minerals
- Inorganic nutrients like iron, calcium, iodine, etc.
- Essential for:
- Enzyme activity
- Nerve and muscle function
- Bone formation
- Osmotic balance
- Too much (e.g., sodium) may cause health problems.
Nutritional Requirements Vary Among Species
- Different species require different nutrients
- Example: Humans need vitamin C; many animals make it themselves
- Diet types (herbivore, omnivore, carnivore) reflect adaptations to nutrient needs
Example: Linoleic Acid Reaction
The conversion of linoleic acid → γ-linoleic acid demonstrates how all four nutrient classes work together:
- Amino acids: enzyme structure
- Vitamin B3: coenzyme (NADH)
- Iron: enzyme cofactor
- Linoleic acid: metabolic substrate
In a Nutshell
Essential nutrients—amino acids, fatty acids, vitamins, and minerals—are the biochemical ingredients of life. While many nutrients can be synthesized internally, these must be obtained through diet to enable key physiological functions and maintain health.