Molecules to metabolism

Nature of science:

Falsification of theories—the artificial synthesis of urea helped to falsify vitalism. (1.9)

• Molecular biology explains living processes in terms of the chemical substances involved.
• Carbon atoms can form four covalent bonds allowing a diversity of stable compounds to exist.
• Life is based on carbon compounds including carbohydrates, lipids, proteins and nucleic acids.
• Metabolism is the web of all the enzyme-catalysed reactions in a cell or organism.
• Anabolism is the synthesis of complex molecules from simpler molecules including the formation of macromolecules from monomers by condensation reactions.
• Catabolism is the breakdown of complex molecules into simpler molecules including the hydrolysis of macromolecules into monomers.

• Syllabus and cross-curricular links:
• Chemistry
• Topic 4 Chemical bonding and structure
• Option B Biochemistry

Aims:

• Aim 7: ICT can be used for molecular visualization of carbohydrates, lipids and proteins in this sub-topic and in 2.3 and 2.4.
• Aim 6: Food tests such as the use of iodine to identify starch or Benedict’s reagent to identify reducing sugars could be carried out.

• Application: Urea as an example of a compound that is produced by living organisms but can also be artificially synthesized.
• Skill: Drawing molecular diagrams of glucose, ribose, a saturated fatty acid and a generalized amino acid.
• Skill: Identification of biochemicals such as sugars, lipids or amino acids from molecular diagrams.

Guidance:

• Only the ring forms of D-ribose, alpha–D-glucose and beta-D-glucose are expected in drawings.
• Sugars include monosaccharides and disaccharides.
• Only one saturated fat is expected and its specific name is not necessary.
• The variable radical of amino acids can be shown as R. The structure of individual R-groups does not need to be memorized.
• Students should be able to recognize from molecular diagrams that triglycerides, phospholipids and steroids are lipids. Drawings of steroids are not expected.
• Proteins or parts of polypeptides should be recognized from molecular diagrams showing amino acids linked by peptide bonds.