Carbohydrates Sugar, Starch, and Fiber

As described in Section 18.14, aldehydes have the general structure R—CHO and ketones have the general structure R—CO—R. 

Notice that glucose is an aldehyde (it contains the —CHO group) with — OH groups on most of the carbon atoms. The many —OH groups make glucose soluble in water (and therefore in blood), which is important in glucose s role as the primary fuel of cells. Glucose is easily transported in the bloodstream and is soluble within the aqueous interior of a cell. 

Glucose is also an example of a hexose, a six-carbon sugar. The general names for monosaccharides have a prefix that depends on the niunber of carbon atoms, followed by the suffix -ose. The most common monosaccharides in living organisms are pentoses and hexoses. 

Other monosaccharides in their ring form include fructose and galactose. 

Fructose, also known as fruit sugar, is a hexose found in many fruits and vegetables and is a major component of honey. Galactose, also known as brain sugar, is a hexose usually foimd combined with other monosaccharides in substances such as lactose (see next section). Galactose is also present within the brain and nervous system of most animals. 

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Carbohydrates Sugar, Starch, and Fiber 696 19.7 Nucleic Acids Molecular Blueprints 716 ... 

The carbohydrates are the sugars, starches, and fibers in food. Foods such as candy, fruits, and sweetened desserts are rich in sugars foods such as pasta, rice, beans, and potatoes are rich in starches and the hulls of wheat, rice, and com, as well as the stmctural material of fruits and vegetables, are rich in fiber. Recall from Chapter 16 that carbohydrates often have the general formula (CH20) and are polyhydroxy aldehydes or ketones, or their derivatives. The OH groups (polyhydroxy) make carbohydrates very soluble in water. Consequently, simple carbohydrates are easily and efficiently transported in the bloodstream to all areas of the body. 

Free oxygen in the air comes from land and water plants and is made by the process of photosynthesis. Using the energy of sunlight, the green parts of the plants transform carbon dioxide and water into oxygen and carbohydrates like sugar, starch, and plant fibers. 

Another substance of ancient acknowledgement is wood fiber, cellulose. Whole samples of tree wood differ from species to species, but carefiiUy extracted and prepared samples obtained from wood were shown by Payen to be a common substance which he called cellulose [45]. Fremy was able to show that sugar, starch and cellulose are aU carbohydrates [46]. 

Macronutrients are carbohydrates (sugars and starches), fats (including essential fatty acids), proteins (including essential amino acids), and fiber. 

Foods supply carbohydrates in three forms starch, sugar, and cellulose (fiber). Starch and sugar are major and essential sources of energy for humans. A lack of carbohydrates in the diet would probably result in an insufficient number of calories in the diet. Cellulose furnishes bulk in the diet. 

Complex carbohydrates are better for us than the simple sugars. Starch, found in rice, potatoes, breads, and cereals, is an excellent energy source. In addition, the complex carbohydrates, such as cellulose, provide us with an important supply of dietary fiber. 

There are three chemical compounds that form the building blocks of food carbohydrates, hits (or hpids), and proteins. Carbohydrate molecules, which are found in fruits, vegetables, starches, and dairy products, consist of atoms of carbon, hydrogen, and oxygen, chemically bonded in a ratio of 1 2 1. Monosaccharides and disaccharides such as glucose, fructose, and sucrose have just one or two molecules of this kind and are known as simple sugars. Polysaccharides like starch, glycogen, and cellulose (an important component of dietary fiber) have several carbohydrate molecules and are known as complex... 

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