Module 5: Carbohydrates PDF

Basic Nutrition MODULE 5: CARBOHYDRATES Learning Outcomes: Upon completion of this module, you will be able to: Describe the classification of carbohydrates. Discuss how carb...

Basic Nutrition MODULE 5: CARBOHYDRATES Learning Outcomes: Upon completion of this module, you will be able to: Describe the classification of carbohydrates. Discuss how carbohydrates are digested and absorbed by our bodies. Describe the different functions of carbohydrates. Identify the potential health risks associated with carbohydrates. Identify good sources of carbohydrates. Identify and discuss the characteristics of the non- nutritive sugar substitutes. Define fiber and the two general types; identify its beneficial effects and possible adverse effects on health; identify its food sources. Prepare healthy meals meal rich in Carbohydrates. Learning Guide Teaching Learning Activities (TLA) Resources 1. Read Module 5: Carbohydrates  Module 5: Carbohydrates 2. Answer Online Quiz  Quiz 3. Perform Laboratory Activity 5  Case Study 4. Perform Case Study  Reference books 5. Participate to Online Discussion  Computer or laptop, internet This module is NOT FOR SALE, DO NOT REPRODUCED 1|Page Introduction Carbohydrates were originally called saccharides, a Greek word, meaning sugars. These are organic compounds abundant in plants and widespread in nature. Important energy source of the entire body and are preferred energy source for red blood cells (erythrocytes), and nerve cells, including those of the brain. Carbohydrates represent a broad group of substances which include the sugars, starches, gums and celluloses. Glucose- The most abundant form of carbohydrate Chemical Nature  A compound made up of carbon, hydrogen and oxygen that is derived from plants and provide energy.  The term carbohydrate literally means “hydrated carbon”. (it contains water)  Chemical abbreviation is CHO (carbon, hydrogen, oxygen)  The ratio of hydrogen to oxygen is 2:1 but a few type of carbohydrates may not follow the typical ratio. However, not all compounds in the classification are true hydrates like deoxyribose, a compound which contains 5 carbons, 10 hydrogens and only 4 oxygen’s.  General formula is C6H12O6 or a monosaccharide. Figure 5-1. Photosynthesis Green plants make carbohydrates through photosynthesis Food Sources of Carbohydrates  The most common food sources of carbohydrates are, sugars, cereal grains and their products (rice, corn, oat, breads and other baked goods, noodles or pasta etc.); 2|Page  root crops, starchy vegetables and dried legumes. Fruits and milk also contribute good amounts of carbohydrates. Classification A. According to complexity 1. Monosaccharides (simple carbohydrates) (mono means “one” and saccharides meaning “sugar”) - the simplest form of sugar which cannot be hydrolyzed into a simpler form. May be grouped according to the number of carbon atoms in the chain: trioses (3-carbon), tetroses (4-carbon), pentoses (5-carbon), hexoses (6-carbon), and heptoses (7-carbon).  Glucose, Fructose, Galactose, Sugar alcohols, Pentoses a) Glucose. Also known as dextrose or grape sugar. Is the most important sugar in human metabolism, hence, the other name for it is the “physiologic sugar”.  Found free in nature: in fruits, honey, corn syrup, sweet corn and certain roots. It is prepared commercially as corn syrup or in its crystalline form by the hydrolysis of starch with acids.  Glucose is the principal product of hydrolysis from starch and cane sugar. In the body, it is formed from starch digestion; in metabolism, glucose is the circulating carbohydrate.  The preferred source of energy for brain and an important source of energy for all cells.  Soluble in hot or cold water. b) Fructose. Is the sweetest of all sugars and found in honey, ripe fruits and some vegetables. It is changed to glucose in the liver to yield energy.  Also called “levulose” or fruit sugar because it is a levorotatory form of sugar, i.e., it rotates a polarized light to the left. c) Galactose. Is not found free in nature but is hydrolyzed from lactose or “milk sugar”. It is changed to glucose in human metabolism, which in turn enters the Krebs cycle to release energy. d) Sugar Alcohols / Polyols. Glucose derivatives. They are neither sugar nor alcohols.  Sugar alcohols sometimes called Nutritive Sweeteners. Are sugar-like compounds that are sweet to taste but yield less kcal per gram. They are use as sucrose substitute (i.e., in candies, chewing gum, beverages, and other foodstuffs. Three important sugar alcohols, sorbitol, xylitol, and mannitol with general formula C6H14O6, have the same sweetening power as glucose.  Sorbitol is absorbed more slowly than other monosaccharides and it has been used to delay the onset of hunger. Excessive consumption of sorbitol causes diarrhea (e.g., an overweight person eating many pieces of sugar- free candies that has sorbitol)  Xylitol is found in the fibers of many fruits and vegetables. It has about the same sweetness as sucrose, but yields less calories (or 2/3 of sugar). Too much xylitol can cause flatulence and diarrhea. 3|Page   Mannitol yields only half the calories per gram (