The two main classes of proteins are simple proteins and conjugated proteins.
Simple Proteins
Simple proteins are composed only of amino acid chains. Upon hydrolysis (a chemical process breaking down a compound with water), they yield only amino acids. Examples include:
- Albumins: Found in egg whites and blood serum.
- Globulins: Present in blood plasma and various tissues.
- Histones: Crucial proteins found in cell nuclei.
The primary structure of a simple protein is its amino acid sequence (Reference: Primary (first level) – Protein structure is a sequence of amino acids in a chain). This sequence then folds and twists into secondary structures (Reference: Secondary (secondary level) – Protein structure is formed by folding and twisting of the amino acid chain), contributing to the protein's overall three-dimensional shape and function.
Conjugated Proteins
Conjugated proteins consist of an amino acid chain (the protein portion) combined with a non-protein component, called a prosthetic group. Examples include:
- Lipoproteins: Proteins bound to lipids (fats). These are crucial for transporting fats in the bloodstream. (Reference: Byjus.com)
- Glycoproteins: Proteins linked to carbohydrates. They play important roles in cell signaling and immune responses.
- Metalloproteins: Proteins containing metal ions, which are essential for their activity. For instance, hemoglobin which includes iron.
The classification of proteins into simple and conjugated categories is based on the components obtained after hydrolysis. Simple proteins yield only amino acids, while conjugated proteins also yield other organic or inorganic substances besides amino acids (Reference: Chemistry LibreTexts).
