Macromolecules and Living Systems

Macromolecules:

• Large molecules made from smaller subunits

• Functions:

  • Provide energy

  • Regulate cell activities

  • Build and repair body tissues

• Metabolism: The sum of all chemical reactions in the body

• Essential Nutrients:

  • Cannot be synthesized by the body

  • Must be obtained through food

Carbohydrates

• Function:

  1. Quick energy source

  2. Material for building cell membranes

• Types:

  1. Simple Sugars:

     • Monosaccharides (single sugars):

       • Glucose – in blood, made by plants

       • Fructose – in fruits

       • Galactose – in milk

     • Disaccharides (double sugars):

       • Sucrose – table sugar

       • Lactose – dairy

       • Maltose – malt products

  2. Complex Carbohydrates (Polysaccharides):

     • Long chains of monosaccharides

       • Starch – plant energy storage (potatoes, rice)

       • Cellulose – plant fiber (indigestible)

       • Glycogen – animal energy storage (liver, muscles)

Lipids

• Characteristics:

  1. Don’t dissolve in water

  2. Found in butter, oils, cream, meats, waxes

• Functions:

  1. Long-term energy storage

  2. Insulation and cushioning of organs

  3. Build cell membranes

  4. Provide more than twice the energy of carbohydrates

• Structure:

  1. Glycerol (3-carbon alcohol) + fatty acid chains

• Types:

  1. Triglycerides:

     • High concentration of energy

     • Insulation 

     • Saturated fats: single carbon bonds (harder to break)

     • Unsaturated fats: double carbon bonds (easier to break)

  2. Phospholipids:

     • Found in cell membranes

     • Hydrophilic(soluble) phosphate head, hydrophobic(insoluble) tails

  3. Waxes:

     • Long-chain fatty acids + alcohol (e.g., earwax)

  4. Sterols:

     • Complex carbon ring structures

     • Examples: cholesterol, sex hormones, steroids, vitamin D

Proteins

• Functions:

  • Structural support (muscles, tissues)

  • Enzymes (speed up chemical reactions)

  • Immunity (antibodies)

  • Transport (membrane proteins, hemoglobin)

  • Hormonal roles

  • Muscle contraction (actin, myosin)

• Structure:

  • Made of amino acids

  • Amino acids have:

    • Central carbon

    • Hydrogen atom

    • Amino group (-NH₂)

    • Carboxyl group (-COOH)

    • R group (varies per amino acid)

• Polypeptides:

  • Chains of amino acids linked by peptide bonds

• Essential Amino Acids:

  • 9 types must be obtained from food
    
    

Nucleic Acids

• Function:

  • Store and transmit genetic information

  • Control cell growth and function

• Types:

  • DNA (Deoxyribonucleic Acid)

  • RNA (Ribonucleic Acid)

Enzymes and Digestion

• Enzymes:

  1. Proteins that catalyze (speed up) chemical reactions

  2. Not used up in the process

• Hydrolysis:

  1. Water breaks macromolecules into smaller units

  2. Requires enzymes

• Types of Digestive Enzymes:

  1. Carbohydrase – breaks carbs → sugars

     • Examples: amylase, lactase, sucrase

  2. Protease – breaks proteins → amino acids

     • Example: pepsin

  3. Lipase – breaks lipids → glycerol + fatty acids

     • Example: pancreatic lipase

  4. Nuclease – breaks nucleic acids → nucleotides

Minerals and Vitamins

• Function:

  • Support chemical reactions

  • Aid growth, immunity, and tissue development

Water

• Functions:

  • Nutrient transport

  • Waste removal

  • Lubrication

  • Regulate temperature

  • Forms blood and mucus

Stages of Food Processing

1. Ingestion – eating food

2. Digestion – mechanical & chemical breakdown

3. Absorption – nutrients enter blood

4. Elimination – remove undigested waste