Nutrition in Human and Social Biology

Nutrition: The Foundation of Life Processes

Nutrition is the biological process through which organisms acquire, metabolize, and utilize essential chemical substances called nutrients to sustain all life functions. This complex process involves multiple systems working synergistically to maintain health and vitality.

Core Nutritional Functions

1. Energy Production

2. Growth & Development

3. Body Regulation

Health Implications

Disease Prevention

Chronic Diseases

  • Cardiovascular disease
  • Type 2 diabetes
  • Certain cancers
  • Osteoporosis

Deficiency Diseases

  • Scurvy (Vitamin C)
  • Rickets (Vitamin D)
  • Anemia (Iron)
  • Goiter (Iodine)

Nutritional Science Components

Component Description Example
Digestive Physiology Mechanical and chemical food breakdown Stomach acid, enzymes
Biochemical Metabolism Nutrient transformation pathways Krebs cycle, glycolysis
Homeostatic Regulation Balance maintenance mechanisms Insulin/glucagon system

Practical Applications

Nutrient Categories

Macro- nutrients Micro- nutrients Water Essential Nutrients

Figure 1: Major categories of nutrients required by the human body

Macronutrients

1. Carbohydrates

Primary energy source (4 kcal/gram):

G F Sucrose Starch Simple Carbohydrates Complex Carbohydrates

Figure 2: Structure of simple vs complex carbohydrates

2. Proteins

Proteins are complex macromolecules composed of amino acids that serve as the fundamental building blocks for all living organisms. They perform more physiological functions than any other nutrient group.

Amino Acid Structure

C N O Variable R Group Amino Group Carboxyl Group General Amino Acid Structure

Figure 3a: Basic structure of an amino acid

Essential vs. Non-Essential Amino Acids

Essential Amino Acids (9)

Cannot be synthesized by the body - must be obtained from food:

  • Histidine
  • Isoleucine
  • Leucine
  • Lysine
  • Methionine
Non-Essential Amino Acids (11)

Can be synthesized by the body when needed:

  • Alanine
  • Asparagine
  • Aspartic acid
  • Glutamic acid
  • Serine

Protein Structure Levels

1. Primary Structure (Amino acid sequence) 2. Secondary Structure (Alpha helices & beta sheets) 3. Tertiary Structure (3D folding) 4. Quaternary Structure (Multiple polypeptide chains)

Figure 3b: Four levels of protein structural organization

Protein Functions in the Body

Function Examples Importance
Structural Collagen, keratin Provides tissue framework
Enzymatic Amylase, lipase Catalyzes biochemical reactions
Transport Hemoglobin, lipoproteins Moves molecules throughout body
Immune Antibodies Defends against pathogens
Hormonal Insulin, growth hormone Regulates physiological processes
Protein Quality Factors

Complete Protein Sources

Eggs Meat Fish Dairy Quinoa

Figure 3c: Complete protein sources containing all essential amino acids

Protein Requirements

AA1 AA2 AA3 Amino Acid Chain Folded Protein Protein Structure

Figure 3: Protein structure from amino acids to folded proteins

3. Fats (Lipids)

Energy storage and cell membranes (9 kcal/gram):

Saturated (No double bonds) Unsaturated (Double bonds) Fatty Acid Structures

Figure 4: Comparison of saturated and unsaturated fatty acids

Micronutrients

Vitamins

  • Fat-soluble: A, D, E, K (stored in body)
  • Water-soluble: B-complex, C (excreted)
  • Function as coenzymes in metabolic reactions
Vitamins A,B,C,D,E,K Coenzymes

Figure 5a: Vitamin functions

Minerals

  • Macrominerals: Ca, P, Mg, Na, K (needed in larger amounts)
  • Trace minerals: Fe, Zn, Cu, I (needed in small amounts)
  • Structural components and electrolytes
Minerals Ca, Fe, K, Na... Bones Electrolytes

Figure 5b: Mineral functions

Digestive System

Human Digestive Tract

Mouth Esophagus Stomach Small Intestine Large Intestine

Figure 6: Major organs of the digestive system

Digestive Processes

1. Mouth

  • Mechanical digestion (chewing)
  • Chemical digestion (salivary amylase)
  • Food formed into bolus

2. Stomach

  • Churning action mixes food
  • Gastric juice (HCl + pepsin)
  • Protein digestion begins

3. Small Intestine

  • Most digestion occurs here
  • Bile emulsifies fats
  • Nutrient absorption

4. Large Intestine

  • Water and mineral absorption
  • Bacterial fermentation
  • Feces formation

Balanced Diet

Food Pyramid

Vegetables Fruits Grains Proteins Dairy Fats/Oils

Figure 7: Modern food pyramid showing recommended dietary proportions

Glossary of Terms

Nutrient
Substance required by organisms for growth and maintenance.
Calorie
Unit of energy; amount needed to raise 1g water by 1°C.
Enzyme
Biological catalyst that speeds up chemical reactions.
Digestion
Breakdown of food into absorbable components.
Absorption
Process of nutrients entering bloodstream.
Metabolism
All chemical reactions in living organisms.
Malnutrition
Imbalance in nutrient intake (deficiency or excess).

Self-Assessment Questions

1. Name the three macronutrients and their energy values.
Carbohydrates (4 kcal/g), Proteins (4 kcal/g), Fats (9 kcal/g)
2. What is the difference between fat-soluble and water-soluble vitamins?
Fat-soluble vitamins (A,D,E,K) are stored in body fat, while water-soluble vitamins (B-complex, C) are not stored and excess is excreted in urine.
3. Describe the role of bile in digestion.
Bile emulsifies fats, breaking them into smaller droplets to increase surface area for enzyme action (lipase).
4. Why is fiber important in the diet even though it's not digested?
Fiber promotes bowel regularity, feeds beneficial gut bacteria, and helps control blood sugar and cholesterol levels.
5. What happens to protein in the stomach during digestion?
Stomach acid (HCl) denatures proteins, and pepsin begins breaking them into smaller polypeptides.

Summary of Key Points