Protein Structure and Function

Protein Fundamentals

• Proteins are composed of monomers called amino acids.
• The bond formed between amino acids in a polypeptide is known as a peptide bond.
• The primary structure of a protein refers to the specific sequence of amino acids in its polypeptide chain.

Protein Structure Levels

• The four levels of protein structure are primary, secondary, tertiary, and quaternary.
• Secondary structure involves interactions such as hydrogen bonds between the peptide backbone, creating alpha helices or beta sheets.
• Tertiary structure is determined by interactions between R-groups of the amino acids.
• Quaternary structure arises when multiple polypeptide chains associate, usually displaying tertiary structure.

Protein Functions

• Antibodies serve as a crucial element of the immune response, recognizing and neutralizing foreign objects.
• Enzymes are proteins that act as catalysts, speeding up chemical reactions in cells.
• Collagen provides structural support in vertebrates, contributing to skin, bones, and connective tissues.

Protein Stability and Diversity

• Folded proteins are energetically more stable due to the reduction of free energy and minimization of hydrophobic areas exposed to water.
• The diversity in protein form and function arises from the unique sequences and arrangements of amino acids.

Protein Folding and Denaturation

• Molecular chaperones assist proteins in achieving proper folding within cells, preventing misfolding.
• A denatured protein loses its native structure and function, often due to external conditions.
• Denaturation can be caused by changes in temperature, pH, or exposure to chemicals.

Advanced Topics

• Prions are misfolded proteins that can induce other proteins to also misfold, leading to disease.
• X-Ray crystallography measures the three-dimensional arrangement of atoms within a crystal, providing insight into protein structure.
• Western Blotting detects specific proteins in a sample using antibody binding.

Chemical Properties of Amino Acids

• The central carbon atom in an amino acid is bonded to an amino group, a carboxyl group, a hydrogen atom, and a variable R-group.
• Polar R-groups tend to be hydrophilic and dissolve easily in water, while nonpolar R-groups are hydrophobic and do not dissolve well.
• Reactive R-groups can participate in chemical reactions, influencing protein function.

Summary

• Overall, proteins are essential biological molecules with complex structures and diverse functions critical to life processes.