by group 6

THE VITAL NUTRIENTS --CARBOHYDRATES

CARBOHYDRATES

WHAT IS CARBOHYDRATES?• A carbohydrate is an organic compound that consists only of carbon, hydrogen, and oxygen, usually with a hydrogen: oxygen atom ratio of 2:1 (as in water) .

• Carbohydrates are not technically hydrates of carbon.  • Carbohydrates are the important sources of energy for our body cells. Recall that carbohydrates are starches and sugars.

• Starches are complex carbohydrates found in bread, cereal, potatoes, rice, corn, beans, and pasta.

• Sugars are simple carbohydrates found mainly in fruits, such as plums, strawberries, and oranges.

HOW DO WE USE CARBOHYDRATES?• During digestion, complex carbohydrates are broken down into simple sugars, such as glucose, fructose, and galactose.

• After digestion, the products are absorbed into the bloodstream through the villi of the small intestine, these sugar molecules circulate to fuel body functions. Some sugar is carried to the liver where it is stored as glycogen.

• Monosaccharides are the major source of fuel for metabolism, being used both as an energy source (glucose being the most important in nature) and in biosynthesis. When monosaccharides are not immediately needed by many cells they are often converted to more space-efficient forms, often polysaccharides. In many animals, including humans, this storage form is glycogen, especially in liver and muscle cells. In plants, starch is used for the same purpose.

WHY CARBOHYDRATES ARE IMPORTANT FOR US?• Carbohydrates are:• the most economical and important source for human to get energy.

• the important materials to constitute the body tissue.• And carbohydrates participate in the composition and activity of cells.

• Foods high in carbohydrate include fruits, sweets, soft drinks, breads, pastas, beans, potatoes, bran, rice, and cereals. Carbohydrates are a common source of energy in living organisms;. Carbohydrate and protein contain 4 kilocalories per gram.

•  Many organisms can easily break down starches into glucose, however, most organisms cannot metabolize cellulose or other polysaccharides. These carbohydrates types can be metabolized by some bacteria and protists. Ruminants and termites, for example, use microorganisms to process cellulose. Even though these complex carbohydrates are not very digestible, they may comprise important dietary elements for humans. Called dietary fiber, these carbohydrates enhance digestion among other benefits.

• Based on the effects on risk of heart disease and obesity, the Institute of Medicine recommends that American and Canadian adults get between 45–65% of dietary energy from carbohydrates. The Food and Agriculture Organization and World Health Organization jointly recommend that national dietary guidelines set a goal of 55–75% of total energy from carbohydrates, but only 10% directly from sugars (their term for simple carbohydrates).

CELLULOSE• Cellulose is an organic compound with the formula (C6H10O5)n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand units.

• Cellulose is the structural component of the primary cell wall of green plants, many forms of algae. Some species of bacteria secrete it to form biofilms. Cellulose is the most common organic compound on Earth. About 33% of all plant matter is cellulose (the cellulose content of cotton is 90% and that of wood is 40–50%). Another complex carbohydrate, is found in all plant cell walls and is not digestible by humans.

• Cellulose (also known as fiber) is still an important item to include in the diet as it helps in the elimination of wastes.

• Sources of fiber include bran, beans, and lettuce.

• Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms that live in their guts. Humans can digest cellulose to some extent, however it is often referred to as "dietary fiber" or "roughage" (e.g. outer shell of maize) and acts as a hydrophilic bulking agent for feces.

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Cellulose in a plant cell Two structures of Cellulose

QUESTIONS1. Which of these is NOT a complex carbohydrate? A. cereal B. pasta C. plums D. beans

2. Which of these is NOT a simple sugar? A. fructose B. galactose C. glucose D. glycogen

3. Which statement below about cellulose is TRUE?A.Cellulose is found in all plant cell walls and is digestible.B.Cellulose is a simple carbohydrate.C.Cellulose can help eliminate wastes and develop red blood calls.D.The sources of cellulose include beans lettuce and brans.

CD

D