Carbohydrates

Healthy Diet Ideally consits of: 50-60% carbohydrates, 20-30% fats, and 10-20% proteins. The body will function better if you follow these proportions for ever meal, rather than in the course of an entire year! (So eat some protein with your poptarts and sugary cereals.) The above proportions are ranges to allow for the slightly different nutritional demands that exist for individuals. For example, diabetic patients need fewer carbohydrates, growing children need a larger amount of protein.

Healthy diet, cont. Not all carbohydrates are the same. Dense complex carbohydrates such as heavy wheat breads, most pastas, and brown rice are better for the body than highly refined, or large surface area carbohydrates such as sugars, white breads, most bagels and white rice. The latter carbohydrates are more rapidly digested, and therefore, sharply increase the glucose level in the blood. This sharp increase in glucose triggers a release of insulin which removes the glucose from the blood. The removal of glucose triggers a hunger response. So highly refined carbohydrates increase your appetite. The dense complex carbohydrates take more time to digest. Therefore, the glucose level never peaks but rather increases to a stable, steady level. This steady glucose level provides a constant source of medium level energy and prevents the sensation of hunger for an extended period of time. Not all fats are the same. Poly and monounsaturated fats such as those found in food oils are considered to be healthier for the body, This will be discussed in a later section.

Carbohydrates Used by the body for energy Consist of carbon, hydrogen, and oxygen Categories of carbohydrates: Monosaccharides or simple sugars Taste extremely sweet Are in a small enough chemical form to cross over cell membranes. They do not need to be digested but are immediately absorbed from the stomach into the blood. Found in fruits or artificially added to desserts Examples to know: fructose, alpha and beta glucose. (Alpha and beta glucose are sterioisomers. Fructose is a structural and functional group isomer to glucose)

Formation of ringed glucose from linear glucose

Carbohydrates cont. Disaccharides Consists of two monosaccharides Taste sweet, but less sweet than a monosaccharide. Examples: sucrose ( sugar cane, table sugar), lactose ( dairy foods), maltose (malts, malt candy) Disaccharides must be broken down into monosaccharides in order to absorb into the blood.

Synthesis of sucrose from fructose and glucose

Carbohydrates cont.. Polysaccharides or complex carbohydrates. Consists of many glucoses bonded together Do not taste sweet Examples to know: starch which is alpha glucose (potatoes, breads, rice, etc), cellulose or beta glucose ( fruits and vegetables- the roughage portion of the plant), glycogen ( stored carbohydrate in liver and muscles) Must be broken down into monosaccharides before being absorbed into the blood. Humans cannot digest cellulose. It is made out of beta glucose so there is no enzyme available to break the bonds between the beta glucoses.

Starch and cellulose

Another diagram for cellulose

The polysaccharides