Proteins and Amino Acids

Composition of Proteins

• Proteins are composed of the elements carbon, hydrogen, oxygen, and nitrogen (in no set ratio)

Structure of Amino Acids

• Amino acids are the building blocks of proteins
• Amino acids have three parts:
  • Amino group (NH2 or NH3+), which acts as a base
  • Carboxyl group (COOH or COO-), which acts as an acid
  • R group (there are 20 different possible R groups)

Formation of Proteins

• Amino acids bond together via dehydration synthesis
• Peptide bonds are formed between carbon and nitrogen atoms, with one water molecule lost
• When two amino acids form the beginning of a chain (with one peptide bond), it is called a dipeptide
• The chain grows to become a tripeptide and eventually a polypeptide
• A polypeptide is also known as a protein

Characteristics of Proteins

• Every protein is different due to the unique order of amino acids
• The order of amino acids affects the chain's structure and function

Levels of Protein Structure

• Primary structure: the order of amino acids joined together with peptide bonds
• Secondary structure: twisting and folding of the primary structure, forming hydrogen bonds
• Tertiary structure: interactions between R groups, determining the protein's 3D shape and function
• Quaternary structure: two or more chains joined to form a functional protein

Denaturation

• Denaturation is the loss of a protein's tertiary or quaternary structure, affecting its function
• Denaturation can occur due to:
  • High temperatures, affecting hydrogen bonds
  • Chemicals, such as heavy metals or acid/basic substances
  • Structural changes

Functions of Proteins

• Structural: proteins make up all structures in living things (e.g., keratin, actin, myosin, collagen)
• Functional: proteins help maintain bodily functions and digest food (e.g., hemoglobin, enzymes)
• Food source: proteins provide energy when carbohydrates and fats are depleted