Building a protein, level by level.

Join amino acids by peptide bonds (one water out each), read N- and C-terminal, coil a right-handed helix, fold to tertiary, and dock 2 alpha + 2 beta chains into haemoglobin.

Build a 6-residue chain, count the water molecules released, then assemble haemoglobin with the right subunit mix.

Peptide chain read from C-terminal; Hb as 4 identical chains.

• Biologists describe protein structure at four levels.
• Primary structure is the sequence of amino acids, the positional information of which comes first, second and so on. The chain is pictured as a line whose left end is the first amino acid, the N-terminal, and whose right end is the last, the C-terminal.
• A protein thread is not a stiff rod. Parts of it coil into a helix, like a spiral staircase, and only right-handed helices are seen in proteins. Other parts fold in other ways. This is the secondary structure.
• The long chain also folds back on itself like a hollow woollen ball. This is the tertiary structure, the three-dimensional view of a protein, and it is essential for many of a protein's biological activities.
• Some proteins are built from several polypeptide chains, called subunits. How these folded subunits sit relative to one another is the quaternary structure.
• Adult human haemoglobin has 4 subunits: two identical alpha subunits and two identical beta subunits.

Teaching this idea? Put the simulation on your own page or LMS with this code.