Food

Function of Food

1. Source of Energy

2. Chemical Building Blocks for Metabolism

3. Growth and Repair

Common Elements Found in All Foods

• Carbon

• Hydrogen

• Oxygen

• Nitrogen

• Sulphur

Common Elements Found in Salts

• Sodium

• Magnesium

• Chlorine

• Potassium

• Calcium

Trace Elements

• Iron

• Copper

• Zinc

Biomolecules

• Biomolecules are chemicals that are made inside a living organism.

• There are four major types of biomolecules found in food:

  1. Carbohydrates

  2. Lipids

  3. Proteins

  4. Vitamins

Carbohydrates

• Composed of carbon, hydrogen, and oxygen.

• Types of Carbohydrates:

  1. Monosaccharide: One sugar unit (e.g., glucose, fructose).

  2. Disaccharide: Two monosaccharides connected (e.g., maltose, lactose).

  3. Polysaccharide: Many monosaccharides connected (e.g., starch, cellulose, glycogen).

• Note:

  • More bonds = More energy content.

  • Only monosaccharides enter the blood; other types must be broken down first.

• Structural Carbohydrate: Cellulose (plant cell walls).

• Carbohydrate Ratio: Ratio of hydrogen to oxygen is 2:1.

• General Formula: Cx(H2O)y

Lipids

• Include oils, fats, and steroids.

• State: Oils are liquid; fats are solid at room temperature.

• Composed of carbon, hydrogen, and oxygen (in different ratios to carbohydrates).

Metabolic Function of Lipids

• Heat insulation in the body.

• Energy storage in cells.

Structural Function of Lipids

• Components of cell membranes.

Types of Lipids:

1. Triglycerides: One glycerol, three fatty acids (found in fatty foods).

2. Phospholipids: One glycerol, two fatty acids, one phosphate head (found in cell membranes).

Proteins

• Composed of carbon, hydrogen, oxygen, nitrogen, and sulphur (non-metal).

Structure of Proteins

• Smallest unit: Amino acid (20 common amino acids).

• Different sequences of amino acids yield different proteins, which fold into a functional 3D shape.

• Bond: Peptide bond between amino acids (peptides -> polypeptides -> proteins).

Metabolic Function of Proteins

• Enzymes and hormones.

Structural Function of Proteins

• Keratin in hair and nails.

• Sources of Protein:

  • Lean meat

  • Fish

  • Eggs

Vitamins

• Required in small amounts for health, cell production, and tissue growth.

1. Water-soluble Vitamin: Vitamin C (source: citrus fruits; deficiency: scurvy).

2. Fat-soluble Vitamin: Vitamin D (sources: milk, eggs, sunshine; deficiency: rickets).

Minerals

• Required in tiny amounts by organisms.

Minerals Required by Plants:

• Calcium (Ca): Helps cell walls attach to one another (source: the soil).

• Magnesium (Mg): Essential for chlorophyll production (source: the soil).

Minerals Required by Animals:

• Calcium (Ca): Needed for teeth and bone formation (source: milk, cheese).

• Iron (Fe): Essential for forming hemoglobin (helps transport oxygen; sources: meat, green vegetables).

Water

Functions:

1. Turgidity in cells (70-95% of cell mass).

2. Solvent.

3. Reaction medium.

4. Heat transport.

5. Nutrient and mineral transport.

Energy Transfer Reactions

Metabolism

• "The sum of all the chemical reactions that occur in an organism."

• Two types:

  1. Anabolic Reactions: Formation of large molecules from smaller ones, requiring energy (e.g., photosynthesis).

  2. Catabolism: Breakdown of large molecules into smaller ones, releasing energy (e.g., respiration).