Scheme of Work Cambridge International as & a level

Extension activity: Learners apply their knowledge by displaying unfamiliar monosaccharides such as cellobiose, or polysaccharides such as chitin, and showing that the same general rules apply to condensation and hydrolysis reactions.

2.2.9 State that triglycerides are non-polar hydrophobic molecules and describe the molecular structure of triglycerides with reference to fatty acids, glycerol and the formation of ester bonds. 2.2.10. Relate the molecular structure of triglycerides to their functions in living organisms. 2.2.11 Describe the molecular structure of phospholipids with reference to their hydrophilic (polar) phosphate heads and hydrophobic (non-polar) fatty acid tails.

Invite leaners to the class whiteboard to attempt to draw the components of a triglyceride from memory, and then show how ester bonds form between the molecules using a pen of a different colour. Through class discussion, relate the molecular structure of triglycerides to their functions in living organisms. (F) Show learners a series of images of organisms for which lipids are of vital importance. Examples include locusts (lipids needed as an energy store for long-distance travel), aquatic mammals (lipids needed for buoyancy/ insulation), and aquatic birds (lipids needed for waterproofing). Discuss their adaptations to their environments; then introduce the idea that their lipid content is higher than most animals and ask why. Learners produce a leaflet to illustrate the importance of lipids in the diet. They generally have a negative press, so their work should aim to persuade the reader of the vital functions of this molecule in accessible language. (I) Give learners an answer, and ask ‘What’s the question?’. Select a range of single-word terms (e.g. triglyceride, glycerol, fatty acids, phosphate head) and simple sentences and provide these to learners. (F)