Proteins

Nature of science:

Looking for patterns, trends and discrepancies—most but not all organisms assemble proteins from the same amino acids. (3.1)

• Amino acids are linked together by condensation to form polypeptides.
• There are 20 different amino acids in polypeptides synthesized on ribosomes.
• Amino acids can be linked together in any sequence giving a huge range of possible polypeptides.
• The amino acid sequence of polypeptides is coded for by genes.
• A protein may consist of a single polypeptide or more than one polypeptide linked together.
• The amino acid sequence determines the three-dimensional conformation of a protein.
• Living organisms synthesize many different proteins with a wide range of functions.
• Every individual has a unique proteome.

Applications and skills:

• Application: Rubisco, insulin, immunoglobulins, rhodopsin, collagen and spider silk as examples of the range of protein functions.
• Application: Denaturation of proteins by heat or by deviation of pH from the optimum.
• Skill: Drawing molecular diagrams to show the formation of a peptide bond.

• Proteomics and the production of proteins by cells cultured in fermenters offer many opportunities for the food, pharmaceutical and other industries.

Aims:

• Aim 7: ICT can be used for molecular visualization of the structure of proteins.
• Aim 8: Obtaining samples of human blood for immunological, pharmaceutical and anthropological studies is an international endeavour with many ethical issues.

• The detailed structure of the six proteins selected to illustrate the functions of proteins is not needed.
• Egg white or albumin solutions can be used in denaturation experiments.
• Students should know that most organisms use the same 20 amino acids in the same genetic code although there are some exceptions. Specific examples could be used for illustration.