The Carbohydrates Sugars Starches and Fibers By Kaci

The Carbohydrates: Sugars, Starches, and Fibers By: Kaci Thompson

Chemistry View of Carbs • Carbohydrates are compounds composed of carbon, oxygen, and hydrogen arranged as monosaccharides or multiples of monosaccharides. • Dietary carbohydrate family includes: – Monosaccharides: single sugars (simple carbs) – Disaccharides: sugars composed of pairs of monosaccharides (simple carbs) – Polysaccharides: large molecules composed of chains of monosaccharides (complex carbs)

Monosaccharides • These three monosaccharides have the same numbers and kinds of atoms, but in different arrangements. These differences account for the differing sweetness. • Glucose • Fructose • Galactose

Glucose • Commonly known as blood sugar or dextrose • Serves as an essential energy source for all the body’s activities • Is one of the two sugars in every disaccharide and the unit from which the polysaccharides are made almost exclusively

Fructose • Sweetest of the sugars • Has the same formula as glucose, but is structured differently • Occurs naturally in fruits and honey • Also in products that have been sweetened with high-fructose corn syrup

Galactose • Occurs naturally as a single sugar in only a few foods • Has the same numbers and kinds of atoms as glucose and fructose, yet is arranged differently

Disaccharides • Disaccharides are pairs of the three monosaccharides mentioned earlier. • Is bound together or separated by condensation and hydrolysis • Maltose (Glucose + Glucose) • Sucrose (Glucose + Fructose) • Lactose (Glucose + Galactose)

Maltose • Consists of two Glucose units • Is produced whenever starch breaks down – as happens in humans during carbohydrate digestion • Also occurs during the fermentation process that yields alcohol • A minor constituent of a few foods, most notably barley

Sucrose • Combination of Glucose and Fructose • In making table sugar, the sucrose is refined from the juices of sugarcane and sugar beets, then granulated • Depending on the extent to which it is refined, it becomes the brown, white, or powdered sugars you see in stores

Lactose • • Combination of Glucose and Galactose Is the principle carbohydrate of milk Known as milk sugar Contributes half of the energy (kcalories) provided by fat-free milk

Polysaccharide • Contain many glucose units and, in some cases, a few other monosaccharides strung together • Glycogen • Starches • Fiber

Glycogen • Storage form of energy in the body; stores glucose for future use • Found to only a limited extent in meats and not at all in plants (rapidly hydrolyzes after slaughter) • Made of many glucose molecules in a highly branched chain • After hormonal “release energy” message arrives at storage sites in the liver or muscle cells, enzymes attack the branches, making glucose available

Starches • Plant cells store glucose as starches • Giant, branched or unbranched chains of hundreds to thousands of glucose molecules • Packed side by side in plants; when you eat these plants, the body hydrolyzes the starch to glucose and uses the glucose for its own energy purposes • Grains are the riches food source of starch, providing much of the food energy we need

Fiber • Structural parts of plants and found in all plant -derived foods • Cannot be broken down by digestive enzymes in the body • Contribute little to no energy since they pass through the body • Soluble or insoluble

Soluble Fiber • Dietary fiber that dissolves in water • Forms gels (viscous) • Easily digested by bacteria in the colon (fermentable) • Often associated with protecting against heart disease and diabetes by lowering blood cholesterol and glucose levels, respectively • Examples: Oats, barley, legumes, and citrus fruits

Insoluble Fiber • Does not dissolve in water • Less readily fermented • Promote bowel movements, alleviate constipation, and prevent diverticular disease • Examples: Whole grains (bran) and vegetables