Chapter 1 Proteins

Chapter 1 - Proteins

Learning Outcomes

  • Chemical elements in protein molecules.

  • Products of protein digestion: amino acids.

  • Definitions and examples:

    • Essential amino acids

    • Non-essential amino acids

    • High biological value proteins

    • Low biological value proteins

    • Complementary proteins

  • Food sources of proteins.

  • Functions of proteins in the body.

  • Cooking processes: denaturation, foaming, coagulation, Maillard browning, gluten development.

Chemical Elements of Proteins

  • Proteins are mainly composed of:

    • Carbon (C)

    • Hydrogen (H)

    • Nitrogen (N)

    • Oxygen (O)

  • These elements form basic units called amino acids.

Formation of Protein Molecules

  • Formed by joining many amino acids through chemical bonds.

Digestion of Proteins

  • Begins in the stomach, with partial digestion.

  • Further broken down into amino acids in the small intestine.

Amino Acids

  • Essential Amino Acids: 9 required from food (e.g., lysine, valine, leucine).

  • Non-essential Amino Acids: 11 produced by the body.

  • Total: 20 different amino acids.

Types of Proteins

Biological Values

  • High Biological Value Proteins:

    • Complete proteins with all essential amino acids.

  • Low Biological Value Proteins:

    • Incomplete proteins lacking one or more essential amino acids.

Complementary Proteins

  • Formed by combining two low biological value proteins (e.g., pulses with grains).

Protein Food Sources

  • High Biological Value Sources:

    • Animal products (beef, chicken, eggs, dairy, fish).

  • Low Biological Value Sources:

    • Plant-based sources (beans, nuts, seeds).

Functions of Proteins

  • Growth and Repair: Supports growth and replaces worn-out cells.

  • Structural Role: Components in skin, muscles, tendons.

  • Transportation: Carries nutrients and gases (e.g., hemoglobin).

  • Enzyme Formation: Proteins make enzymes for digestion.

  • Immunity: Antibodies protect against harmful microorganisms.

  • Energy Reserve: Used when carbs and fats are insufficient.

  • Body Movement: Integral to muscle composition.

Reactions Involving Proteins

  • Denaturation: Alteration of protein structure due to heat/pH changes.

  • Foaming: Proteins trap air when beaten (e.g., egg whites for meringues).

  • Coagulation: Solidifying of proteins (e.g., frying eggs).

  • Gluten Development: Formation of a protein network in wheat flour mixed with water.