Nature's Chemistry: Proteins

Nature’s Chemistry: Proteins

Overview of Proteins

  • Proteins are one of the most crucial biological molecules, vital for life processes.
  • They are polymers made up of amino acids, which are monomer units.
  • There are 20 different amino acids that can be combined in countless ways to create different proteins.
  • The general structure of an amino acid includes a central carbon atom, an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a variable side group (R).

Structure of Proteins

  • Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.
  • The primary structure is the sequence of amino acids in the polymer.
  • The secondary structure involves the formation of alpha helices and beta pleated sheets due to hydrogen bonding.
  • The tertiary structure is the three-dimensional shape that a protein assumes, largely due to interactions between the R groups of the amino acids.
  • The quaternary structure involves the arrangement and interaction of multiple polypeptide chains in a protein.

Properties of Proteins

  • A protein’s properties, such as its shape, size, and function, are determined by its unique sequence of amino acids and its overall structure.
  • Proteins are typically soluble in water, and show an amphoteric behaviour as they can act as both acids and bases.
  • Exterior amino acids are usually hydrophilic (water-loving) whilst interior ones are hydrophobic (water-fearing), allowing proteins to fold and function in a watery cell environment.

Reactions Involving Proteins

  • Proteins can react with other molecules in the body to function as enzymes, facilitating biochemical reactions at body temperatures.
  • Proteins can also be denatured – their structure can be irreversibly changed – by factors like changes in pH, temperature, or exposure to certain chemicals.

Role and Uses of Proteins

  • Proteins play diverse roles in organisms, including acting as enzymes, hormones, and antibodies.
  • Proteins also provide structural support for cells and tissues and are used for transport of other molecules throughout the body.
  • In industry, proteins are used in food production, for example in baking and brewing, and in laundry detergents where enzymes break down stains.