Biomolecules carbohydrates

Complex carbohydrates are made up of two or more simple sugars linked together. 

A monosaccharide with an aldehyde carbonyl group is an aldose. 

A monosaccharide with a ketone carbonyl group is a ketose. 

indicate the number of carbons in the monosaccharide, n. Monosaccharides (Sections 25.2 - 25.7). 

The carbonyl carbon is placed at or near the top of the Fischer projection. 

Hexokinase catalyzes the phosphorylation of glucose, the first step in carbohydrate metabolism. 

Carbohydrates occur in every living organism. The sugar and starch in food and the cellulose in wood, paper, and cotton are nearly pure carbohydrates. Modified carbohydrates form part of the coating around living cells, other carbohydrates are part of the nucleic acids that carry our genetic information, and still others are used as medicines. 

The word carbohydrate derives historically from the fact that glucose, the first simple carbohydrate to he obtained in pure form, has the molecular formula CeHi206 and was originally thought to be a hydrate of carbon, C6(H20)6- This view was soon abandoned, but the name survived. Today, the term carbohydrate is used to refer loosely to the broad class of polyhydroxylated aldehydes and ketones commonly called sugars. Glucose, also known as dextrose in medical work, is the most familiar example. 

Online homework forthls chapter can be assigned in Organic OWL. 

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Lipids differ from the other classes of naturally occuning biomolecules (carbohydrates, proteins, and nucleic acids) in that they are more soluble in nonpolar to weakly polar- solvents (diethyl ether, hexane, dichloromethane) than they are in water. They include a variety of str-uctural types, a collection of which is introduced in this chapter. 

We ll see later in this chapter and again in Chapter 29 that carbonyl condensation reactions occur frequently in metabolic pathways. In fact, almost all classes of biomolecules—carbohydrates, lipids, proteins, nucleic acids, and many others—are biosynthesized through pathways that involve carbonyl condensation reactions. As with the or-substitution reaction discussed in the previous chapter, the great value of carbonyl condensations is that they are one of the few general methods for forming carbon-carbon bonds, thereby making it possible to build larger molecules from smaller precursors. We ll see how and why these reactions occur in this chapter. 

Chapter 25, Biomolecules Carbohydrates—A new Section 25.7 on the eight essentia carbohydrates has been added, and numerous content revisions have been made. 

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