Monosaccharides Carbohydrates that cannot disaccharides

Carbohydrates are polyhydroxy aldehydes, polyhydroxy ketones, or compounds that can be hydrolyzed to them. A carbohydrate that cannot be hydrolyzed to simpler compounds is called a monosaccharide. A carbohydrate that can be hydrolyzed to two monosaccharide molecules is called a disaccharide. A carbohydrate that can be hydrolyzed to many monosaccharide molecules is called a polysaccharide. 

Carbohydrates are classified based upon the products formed when they are hydrolyzed. Monosaccharides are simple sugars that cannot be broken down into simpler sugars upon hydrolysis. Examples of monosaccharides are glucose, ribose, deoxyribose, and fructose. Disaccharides contain two monosaccharide units and yield two monosaccharides upon hydrolysis. Examples of disaccharides are lactose, maltose, and sucrose. Polysaccharides are polymers of monosaccharide units and yield many individual monosaccharides upon hydrolysis. Examples of polysaccharides are starch, glycogen, and cellulose. 

The simplest carbohydrate, called a monosaccharide, is composed of a structure that cannot be hydrolyzed to simpler polyhydroxylic compounds. A disaccharide is a carbohydrate that contains two of these basic units, and a polysaccharide contains many polyhydroxylic monomers. 

The term carbohydrate includes a wide range of molecules which in many cases are quite complex structures. In chemical terms a carbohydrate is either a polyhydroxy aldehyde, a polyhydroxy ketone or, alternatively, it is a compound that can be hydrolysed to such a structure. The smallest unit that cannot be hydrolysed any further is called a monosaccharide. Glucose (Fig. 11.4.1) is the most abundant monosaccharide known and is by far the most important. Other examples include fructose and mannose. A carbohydrate which has been hydrolysed to two monosaccharide units is cabled a disaccharide and the best known example is sucrose, which is composed of a unit of glucose covalently linked to a unit of fructose. The nomenclature system continues in a logical fashion until one can refer to an ohgosaccharide as being a chain composed of several monosaccharide units. Depending upon whether a monosaccharide is an aldehyde or a... 

Carbohydrates are divided into groups depending on how many monomers are combined by condensation polymerization monosaccharides (Latin saccharum, sugar ), disaccharides, trisaccharides (etc.), and polysaccharides. Monosaccharides are simple sugars that cannot be broken down into smaller carbohydrate units by acid hydrolysis. In contrast, hydrolysis of a disaccharide or trisaccharide yields two or three monosaccharides (either the same or different), while complete hydrolysis of a polysaccharide produces many monosaccharides (sometimes thousands of them). 

The simplest carbohydrates, those that cannot be hydrolyzed into simpler carbohydrates, are called monosaccharides. On a molecular basis, carbohydrates that undergo hydrolysis to produce only 2 molecules of monosaccharide are called disaccharides those that yield 3 molecules of monosaccharide are called trisaccharides and so on. (Carbohydrates that hydrolyze to yield 2-10 molecules of monosaccharide are sometimes called oligosaccharides.) Carbohydrates that yield a large number of molecules of monosaccharides (>10) are known as polysaccharides. 

The simplest carbohydrates are the monosaccharides. A monosaccharide cannot be split or hydrolyzed into smaller carbohydrates. One of the most common carbohydrates, glucose, C6H12O6, is a monosaccharide. A disaccharide consists of two monosaccharide units joined together, which can be split into two monosaccharide units. For example, ordinary table sugar, sucrose, C12H22O11, is a disaccharide that can be split by water (hydrolysis) in the presence of an acid or an enzyme to give one molecule of glucose and one molecule of another monosaccharide, fructose. 

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