Understandings:
- With one exception, amino acids are chiral, and only the L-configuration is found in proteins.
- Naturally occurring unsaturated fat is mostly in the cis form, but food processing can convert it into the trans form.
- D and L stereoisomers of sugars refer to the configuration of the chiral carbon atom furthest from the aldehyde or ketone group, and D forms occur most frequently in nature.
- Ring forms of sugars have isomers, known as α and β, depending on whether the position of the hydroxyl group at carbon 1 (glucose) or carbon 2 (fructose) lies below the plane of the ring (α) or above the plane of the ring (β).
- Vision chemistry involves the light activated interconversion of cis- and trans- isomers of retinal.
Applications and skills:
- Description of the hydrogenation and partial hydrogenation of unsaturated fats, including the production of trans-fats, and a discussion of the advantages and disadvantages of these processes.
- Explanation of the structure and properties of cellulose, and comparison with starch.
- Discussion of the importance of cellulose as a structural material and in the diet.
- Outline of the role of vitamin A in vision, including the roles of opsin, rhodopsin and cis- and trans-retinal.
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International-mindedness:
- Different countries have very different standards of food labelling with respect to its chemical content, including the type of fats present.
Utilization:
- Syllabus and cross-curricular links:
- Topic 10.1—organic functional groups
- Topic 20.1—organic reactions
- Topic 20.3—stereoisomerism
- Option A.4—intermolecular/London forces
Aims:
- Aim 8: Ethical questions arise through the use of saturated and trans-fats, particularly in the fast-food industry.
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