What are Proteins?
Proteins are essential macronutrients that serve as the building blocks of life. They are made up of chains of amino acids, which are organic compounds composed of carbon, hydrogen, oxygen, nitrogen, and sometimes sulfur. Proteins play a crucial role in building, repairing, and maintaining tissues, as well as supporting numerous physiological processes.
Functions of Proteins:
- Structural Role: Proteins like collagen and keratin provide structure to skin, bones, hair, and nails.
- Enzymatic Activity: Enzymes, which are proteins, catalyze biochemical reactions in the body.
- Transportation: Hemoglobin, a protein, transports oxygen in the blood.
- Immune Support: Antibodies are proteins that help fight infections.
- Energy Source: Proteins can provide energy when carbohydrates and fats are insufficient.
Types of Proteins
Proteins can be categorized based on their source, function, and structure.
1. By Source
- Animal-Based Proteins:
- Found in meat, fish, eggs, dairy, and poultry.
- Rich in all essential amino acids, making them complete proteins.
- Plant-Based Proteins:
- Found in legumes, nuts, seeds, grains, and vegetables.
- Often incomplete but can be combined to provide all essential amino acids (e.g., rice and beans).
2. By Function
- Structural Proteins: Provide support and strength (e.g., collagen, keratin).
- Enzymatic Proteins: Speed up chemical reactions (e.g., lactase, amylase).
- Transport Proteins: Move substances within the body (e.g., hemoglobin).
- Hormonal Proteins: Regulate bodily functions (e.g., insulin, glucagon).
- Defensive Proteins: Protect the body from pathogens (e.g., antibodies).
- Storage Proteins: Store essential nutrients (e.g., ferritin for iron).
- Contractile Proteins: Help muscles contract (e.g., actin, myosin).
3. By Structure
- Fibrous Proteins:
- Long and thread-like, providing structural support (e.g., collagen, elastin).
- Globular Proteins:
- Compact and spherical, involved in metabolic functions (e.g., enzymes, hemoglobin).
- Membrane Proteins:
- Embedded in cell membranes, aiding in cell signaling and transport (e.g., receptors, ion channels).
Complete vs. Incomplete Proteins
- Complete Proteins: Contain all nine essential amino acids (e.g., meat, eggs, quinoa, soy).
- Incomplete Proteins: Lack one or more essential amino acids (e.g., beans, rice, nuts).
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