Carbohydrates

1. Carbohydrates King Saud University Al-Riyadh Community college By: Murad Adnan Sawalha

2. Outline Nature of carbohydrates Classes of carbohydrates - Simple carbohydrates (monosaccharide, disaccharides) - Complex carbohydrates (polysaccharides) Functions of carbohydrates Food sources of carbohydrates Digestion of carbohydrates Body needs for carbohydrates

3. Nature of carbohydrates Basic fuel source: - Energy is the power an organism requires to do work, this energy system must have a basic fuel supply. - Photosynthesis: transform solar energy into carbohydrates (the stored fuel form of plants. - Because the human body can quickly breakdown sugars & starches, they provide the major sources of energy, in the form of calories. - �Quick energy� foods.

4. Nature of carbohydrates Energy production system: - 3 steps to produce energy from a basic fuel supply: 1) Change the basic fuel to a refined fuel that the machine is designed to use. 2) Carry this refined fuel to the places that need it. 3) Burn this refined fuel in the special equipment set up at these places. - Example: (1) In human body, the body digests its basic fuel, carbohydrates, changing it to glucose. (2) The body then absorb & through blood circulation, carries this refined fuel to cells that need glucose. (3) Glucose is burned in these cells, & energy produced through the process of metabolism.

5. Nature of carbohydrates Dietary importance: - Carbohydrates are widely available & easily grown - Low cost in comparison with other food items. - Easily stored, & they can be kept for long periods without spoilage. - Most of the total Kcalories in our diet come from carbohydrates.

6. Classes of carbohydrates A carbohydrates is composed of carbon (C), hydrogen (H), and oxygen (O). (CH2O)n when n = 5 then C5H10O5 Saccharide: chemical name for sugar molecules comes from the Latin word saccharum, meaning �sugar�. Carbohydrates: are classified according to the number of sugar, or Saccharide units.

7. Classes of carbohydrates Monosaccharide: single (mono) molecules of sugar, one sugar unit. They are quickly absorbed from the intestine into the blood stream and carried to the liver. Glucose, fructose, lactose. Disaccharide: �double sugar� composed of 2 sugar unit. - Sucrose, Lactose, Maltose. Polysaccharide: carbohydrates consisting of many (poly) sugar molecules. - Starch, Glycogen, Dietary fiber.

8. Monosaccharide Glucose: - Is the form of sugar circulating in the blood and is the primary fuel to the cells. - The blood supply comes mainly from the digestion of starch, & sometimes called dextrose. - Is a moderately sweet sugar. Fructose: is found mainly in fruits, consider the sweetest of the simple sugars. Galactose: comes mainly from the digestion of milk sugar, or lactose.

9. Disaccharides Sucrose: - Is common table sugar, its two sugar units are glucose & fructose. Lactose: - Is the milk sugar, formed in mammary glands - Its two single sugar units are glucose & Galactose. - Not found in plants. - Aids in the absorption of calcium & phosphorus. Maltose: - The two single sugar units that compose maltose are double glucose molecule.

10. Polysaccharides 1) Starch: - They are found in grains, legumes, and other vegetables, and some fruits. - Breakdown more slowly and supply energy over a longer period of time. - Most important dietary carbohydrate - The major food sources of starch include grains in the form of pasta, crackers, bread, and other baked goods, legumes in the form of beans, & peas, potatoes, rice, corn, & bulgur.

11. Polysaccharides - Whole grains: is used for food products such as flours, breads, or cereals that are produced from unrefined grain, which is grain that still retains its outer bran layers and inner germ endosperm and their nutrients (i.e. dietary fiber, minerals, & vitamins) - Enriched grains: are refined grain products to which key nutrients, usually minerals (i.e. iron), and vitamins (i.e. A, C, D, thiamin, riboflavin, & niacin), have been added. 2) Glycogen: found in animal muscle tissue, and liver 3) Dietary fiber

12. Polysaccharides: Dietary fiber Dietary fiber: in humans there is a lack in the necessary enzymes to digest dietary fiber, used to treat gastrointestinal problems. - Cellulose: helps move the food mass along, stimulates normal muscle action in the intestine, and forms feces for elimination of waste products, the main sources are the stems and leaves of vegetables and the coverings of seeds and grains. - Noncellulose polysaccharides: they absorb water and swell to a larger bulk, thus slowing the emptying of the food mass from the stomach, and preventing spastic colon. - Lignin: is a large compound that forms the woody part of certain plants, it also combines with bile acids and cholesterol in the human intestine, preventing their absorption

13. Other sweeteners Used as sugar replacers 2 types: 1) Nutritive sweeteners: - They are sweeteners such sugar alcohols that contribute to total calorie intake. - Sugar alcohols (sorbitol, mannitol, & xylitol) - 2-3 kcalories/gram. - Sorbitol: sucrose substitute. - They are absorbed slowly in the small intestine. - Use for diabetic patients - Excessive amount= diarrhea. - lowered risk than sugar to cause dental caries.

14. Other sweeteners 2) Nonnutritive sweeteners: - Alternative sweeteners. - Are sugar substitutes that do not have any caloric value. - Sweet taste without energy. - Commonly used are aspartame & saccharin. - Sweeter than table sugar.

15. Functions of carbohydrates 1) Primary energy function: (a) Basic fuel supply: - Primary fuel for the body. - Fuel factor for carbohydrates is 4 kcal/gram. (b) Reserve of fuel supply: - Glycogen reserves fuel supply - Individual must eat carbohydrate foods regularly to meet energy demand (to maintain blood glucose level & prevent a breakdown of fat and protein in tissue).

16. Functions of carbohydrates 2) Special tissue functions: - Liver: glycogen reserves in the liver & muscles, protect cells from depressed metabolic function. - Protein & fat: (1) Carbohydrates protects protein to be used in tissue growth & maintenance (2) Prevent rapid breakdown of fat & produce ketones (strong acid), this action called antiketogenic effect.

17. Functions of carbohydrates 2) Special tissue functions: - Heart: fatty acids are the regular fuel for energy, in emergency situation glycogen. - Central nervous system: the brain need continues supply of glucose, otherwise low sugar cause brain damage.

18. Food sources of carbohydrates Starches: - Such as grain products (corn, bread), & vegetables (tomatoes, onions). - Provide energy for prolong period. - Basic component in the balanced diet. - Unrefined forms are considered sources of fiber & other nutrients. Sugars: - Such as candies, fruits, milk. - are necessary for health but in a moderate amount. - High sugar diets= risk for dental caries & obesity.

19. Digestion of carbohydrates Mouth: digestion by 2 types of actions: 1) Mechanical process by mastication: breakdown food into small particles, & mixed with saliva. 2) Chemical process: specific enzymes such as salivary amylase breaks into smaller usable metabolic products. Example: amylase breakdown starch into dextrin, and disaccharides. - Monosaccharides travel to stomach & small intestine for absorption without further digestion.

20. Digestion of carbohydrates Stomach: - Peristalsis: wavelike contractions of the muscle fiber mixes food particles with gastric secretions. - Hydrochloric acid: stops the action of salivary amylase. - In the lower part of the stomach: the food mass become thick creamy (chyme) - Emptying chyme to duedenum.

21. Digestion of carbohydrates Small intestine: - peristalsis continue mechanical digestion. - Pancreatic secretions: enter the duodenum through the common bile duct. Pancreatic amylase: (1) digest starch to maltose, (2) reduces maltose to monosaccharides, (3) breakdown of disaccharides to monosaccharides. - Intestinal secretions: enzymes attached to �special cells on the microvilli� (bruch border), sucrase, lactase, & maltase convert dissaccharides (sucrose, lactose, maltose) into monosaccharides (glucose, galactose, & fructose) - Lactose intolerance: inability to break lactose into glucose & galactose (lack of lactase enzyme), symptoms include bloating, gas, abdominal pain, & diarrhea.

22. Body needs for carbohydrates (CHO) Dietary reference intake: - 45%-65% of an adult total caloric intake should come from carbohydrate foods. - Means 225-325g of CHO for a 2000kcal/day diet - Recommended fiber: choosing carbohydrates contain whole grain cereals, legumes, vegetables, & fruits. - Sugars no more than 25% of total calories. Dietary guidelines for americans: - As in food guide pyramid: grains, fruits, & vegetables are the foundation of a healthy diet.

23. Thank you for your listening