Notes

Carbohydrates are biological molecules made of carbon, hydrogen, and oxygen in a ratio of roughly one carbon atom to one water molecule.

This composition gives carbohydrates their name: they are made up of carbon plus water.

Carbohydrate chains come in different lengths, and biologically important carbohydrates belong to three categories: monosaccharides, disaccharides, and polysaccharides.

Monosaccharides are simple sugars, the most common of which is glucose. Monosaccharides have a formula of (CH20) and they typically contain three to seven carbon atoms.

If the sugar has an aldehyde group, meaning that the carbonyl C is the last one in the chain, it is known as an aldose.

If the carbonyl C is internal to the chain, so that there are other carbons on both sides of it, it forms a ketone group and the sugar is called a ketose.

Sugars are also named according to their number of carbons

trioses (three carbons)
pentoses (five carbons)
hexoses (six carbons).

Amylose consists entirely of unbranched chains of glucose monomers connected by 1-4 linkages.

Amylopectin is a branched polysaccharide. Although most of its monomers are connected by 1-4 linkages, additional 1-6 linkages occur periodically and result in branch points.

If there are only single bonds between neighboring carbons in the hydrocarbon chain, a fatty acid is said to be saturated. (The thing that fatty acids are saturated with is hydrogen; in a saturated fat, as many hydrogen atoms as possible are attached to the carbon skeleton.)

When the hydrocarbon chain has a double bond, the fatty acid is said to be unsaturated, as it now has fewer hydrogens. If there is just one double bond in a fatty acid, it’s monounsaturated, while if there are multiple double bonds, it’s polyunsaturated.