Guiding Questions:

• In what ways do variations in form allow diversity of function in carbohydrates and lipids?

• How do carbohydrates and lipids compare as energy storage compounds?

Linking Questions:

• How can compounds synthesized by living organisms accumulate and become carbon sinks?

• What are the roles of oxidation and reduction in biological systems?

Learning objectives:

The Importance of Carbon

B1.1.1 Chemical properties of a carbon atom allowing for the formation of diverse compounds upon which life is based: understand the nature of a covalent bond. Students should also understand that a carbon atom can form up to four single bonds or a combination of single and double bonds with other carbon atoms or atoms of other non-metallic elements. Include among the diversity of carbon compounds examples of molecules with branched or unbranched chains and single or multiple rings. NOS: Students should understand that scientific conventions are based on international agreement (SI metric unit prefixes “kilo”, “centi”, “milli”, “micro” and “nano”).

Carbohydrates

B1.1.4 Form and function of monosaccharides: recognize pentoses and hexoses as monosaccharides from molecular diagrams showing them in the ring forms. Use glucose as an example of the link between the properties of a monosaccharide and how it is used, emphasizing solubility, transportability, chemical stability and the yield of energy from oxidation as properties.

B1.1.2 Production of macromolecules by condensation reactions that link monomers to form a polymer: be familiar with examples of polysaccharides (polypeptides and nucleic acids).

B1.1.3 Digestion of polymers into monomers by hydrolysis reactions: Water molecules are split to provide the -H and -OH groups that are incorporated to produce monomers, hence the name of this type of reaction.

B1.1.5 Polysaccharides as energy storage compounds: Include the compact nature of starch in plants and glycogen in animals due to coiling and branching during polymerization, the relative insolubility of these compounds due to large molecular size and the relative ease of adding or removing alpha-glucose monomers by condensation and hydrolysis to build or mobilize energy stores.

B1.1.6 Structure of cellulose related to its function as a structural polysaccharide in plants: Include the alternating orientation of beta-glucose monomers, giving straight chains that can be grouped in bundles and cross-linked with hydrogen bonds.

B1.1.7 Role of glycoproteins in cell–cell recognition: Include ABO antigens as an example.

Lipids

B1.1.8 Hydrophobic properties of lipids: Lipids are substances in living organisms that dissolve in non-polar solvents but are only sparingly soluble in aqueous solvents. Lipids include fats, oils, waxes and steroids.

B1.1.9 Formation of triglycerides and phospholipids by condensation reactions: One glycerol molecule can link three fatty acid molecules or two fatty acid molecules and one phosphate group

B1.1.10 Difference between saturated, monounsaturated and polyunsaturated fatty acids: Include the number of double carbon (C=C) bonds and how this affects melting point. Relate this to the prevalence of different types of fatty acids in oils and fats used for energy storage in plants and endotherms respectively.

B1.1.11 Triglycerides in adipose tissues for energy storage and thermal insulation: understand that the properties of triglycerides make them suited to long-term energy storage functions. Students should be able to relate the use of triglycerides as thermal insulators to body temperature and habitat.

B1.1.12 Formation of phospholipid bilayers as a consequence of the hydrophobic and hydrophilic regions: use and understand the term “amphipathic”.

B1.1.13 Ability of non-polar steroids to pass through the phospholipid bilayer: Include oestradiol and testosterone as examples. Students should be able to identify compounds as steroids from molecular diagrams.