Proteins and Nucleic Acids

Proteins and Nucleic Acids

Structure of Proteins

  • Proteins are large biomolecules consisting of one or more long chains of amino acid residues.
  • Proteins are formed when amino acids link together via peptide bonds in a chain. This chain is known as a polypeptide.
  • The function of a protein is determined by its particular amino acid sequence and in turn, by the shape into which it folds.
  • The structure of proteins can be broken down into four levels: primary, secondary, tertiary, and quaternary structure.

Functions of Proteins in Organisms

  • Proteins play many critical roles in living organisms, including catalysing metabolic reactions as enzymes, DNA replication, responding to stimuli, and transporting molecules from one location to another.
  • Proteins such as antibodies, insulin, and hormones play a vital role in the immune system and metabolic processes.
  • Proteins like collagen and keratin form structures in animals, providing mechanical support and protection.

Structure of Nucleic Acids

  • Nucleic acids are polymers composed of nucleotides, which itself consists of three parts: a sugar, a phosphate group, and a nitrogenous base.
  • There are two types of nucleic acids, DNA (Deoxyribonucleic acid) and RNA (Ribonucleic acid). DNA contains the genetic instructions used in the development and functioning of all known living organisms.
  • In DNA, the sugar is deoxyribose and nitrogenous bases are adenine (A), thymine (T), guanine (G), and cytosine (C). In RNA, the sugar is ribose and the base uracil (U) replaces thymine.

Functions of Nucleic Acids in Organisms

  • Nucleic acids are responsible for storage, replication, and expression of genetic information in cells.
  • DNA, acting as the cell’s “instruction manual,” controls the cell’s activities and characteristics.
  • RNA molecules perform a host of roles in the process of gene expression, including acting as a messenger between DNA and the protein synthesis machinery and as molecular machinery in that process.

Metabolic Pathways of Proteins and Nucleic Acids

  • Protein synthesis (known as translation) occurs in the ribosomes of the cell, using the instructions encoded in the mRNA (a type of RNA).
  • Proteins can be broken down through a process called proteolysis and their constituent amino acids can be re-used in new proteins or catabolized for energy.
  • DNA replication is a process where DNA makes a copy of itself during cell division, ensuring that each new cell has an exact copy of the DNA.
  • Transcription is the first step in gene expression, where the DNA sequence in a gene is copied into RNA.

Role of Proteins and Nucleic Acids in Diet and Health

  • Eating protein-rich foods contributes to muscle repair and growth and is vital for a healthy immune system.
  • A balance of all 20 amino acids, obtained from the diet, is necessary for the body to create all the proteins it needs.
  • Dietary nucleic acids are mainly broken down and used as an energy source or used in the synthesis of new nucleotides within the body. They are commonly found in foods such as beans and lentils, meat, and certain fruits.