Amino acids and Proteins 🥚🥩

• Amino acid general structure:

  Amine group, Carboxyl group and R group

  
• Elements present in proteins:

  carbon

  oxygen

  nitrogen

  hydrogen

  Rarely sulphur
• A peptide bond is formed when two or more amino acids combine in a condensation reaction. Two amino acids make a dipeptide. This reaction occurs in ribosomes.
• One molecule of water is made for every peptide bond which is formed in a condensation reaction of amino acids.
• To break a peptide bond, a molecule of water must be added in a hydrolysis reaction, this is carried out by protease enzymes in the digsestive system.
• A protein is made only when a polypeptide is folded into its correct shape for its specific function.
• What is the primary structure of an amino acid?

  The specific order of the amino acids in a polypeptide.
• The primary structure of a protein helps to determine the final 3 dimensional shape of the protein molecule, so by changing it slightly, i.e. by adding or removing a few amino acids, the protein can be modified to perform a different function.
• The primary structure of a polypeptide is determined by the DNA sequence of the gene which encodes that polypeptide.
• The secondary structure of a protein is as a result of hydrogen bonds between oxygen in the carboxyl groups and hydrogen in the amine groups. The oxygen has a partial negative charge adn the hydrogen a partial positive charge. The hydrogen bonds result in one of two shapes: alpha helix, or a beta-pleated sheet.
• Tertiary structure is the 3D folding of the polypeptide chain, it is how the secondary structures fold together. The tertiary structure determines the shape of the active site of an enzyme.
• Proteins can either have a single polypeptide chain or multiple. Those that only have one chain, are limited to having a tertiary structure and not a quaternary one.
• Proteins with several polypeptide chains working together as a large molecule are said to have a quaternary structure.
• Proteins are only said to have a quaternary structure if they contain at least 2 subunits (aka polypeptides).
• Some quaternary structure proteins also have prosthetic groups which are non-protein molecules within the protein. They help the protein to carry out its role.
• Proteins which contain prosthetic groups are identified as conjugated proteins.
• The primary structure of a protein only consists of peptide bonds
• The secondary structure of a protein contains hydrogen bonds.