Download BIOL103 Ch 4 Carbohydrates SP16_for Students.pptx

2/16/16 What Are Carbohydrates? Chapter 4 Carbohydrates: Simple Sugars and Complex Chains BIOL 103, Spring 2016 Simple Sugars •  Monosaccharides – Glucose – Fructose – Galactose •  Sugars, starches, and fibers •  Major food sources: Plants – Produced during photosynthesis •  Two main carbohydrate types – Simple (Sugars) – Complex (Starches and fibers) Monosaccharides •  Glucose/Dextrose – Most abundant simple sugar in nature
– Gives food a mildly sweet flavor – Usually joined to another sugar in foods to form disaccharides, starch, dietary fiber – Provides energy to body cells •  Blood sugar levels •  Only fuel source used by brain 1 2/16/16 High Fructose Corn Syrup Monosaccharides •  Fructose/Levulose – “fruit sugar” – Tastes the sweetest of all the sugars – Occurs naturally in fruits and vegetables – Found in fruits, vegetables, honey, and corn syrup •  Why do we use it? –  Before 1970s à U.S. cane sugar à too expensive –  1980s, food companies switched to cheaper corn •  Pepsi/Coke switched in 1984 High Fructose Corn Syrup •  How is it made? 1.  Convert glucose à fructose, using isomerase 2.  Add corn syrup, then a specific ra]o of glucose •  Example: HFCS 55 (so` drinks) Why is High Fructose Corn Syrup associated with weight gain? 1.  Corn is cheap à cheaper soda à supersize à drink more à more calories 2.  Fructose does NOT release insulin and lep:n à does not feel full à drink more à more calories •  However, note that overconsump]on of ANY forms of sugar will contribute to weight gain. 2 2/16/16 Monosaccharides •  Galactose – Rarely occurs as a monosaccharide in food – Usually bonds to glucose to form lactose •  Primary sugar in milk and dairy products Disaccharides •  Sucrose: glucose + fructose – “Table sugar” – Made from sugar cane and sugar beets – Listed as sugar on food labels •  Lactose: glucose + galactose – “Milk sugar” – Found in milk and milk products Simple Sugars •  Disaccharides: Consist of two monosaccharides linked together – Sucrose: glu + fru – Lactose: glu + gal – Maltose: glu + glu •  Linked by glycosidic bonds Lactose Intolerance •  Who has it? –  Anyone who does not have enough lactase, which normally converts (lactose à glucose + galactose) •  Why do you get it? –  Lactase nonpersistence (most common) –  Injury/infec]on to intes]ne usually during infancy –  Developmental lactase deficiency in premature infants –  Congenital lactase deficiency: rare gene]c disorder from birth 3 2/16/16 Disaccharides •  Maltose: glucose + glucose – “Malt sugar” – Seldom occurs naturally in foods – Product of starch breakdown – Found in germina]ng cereal grains Complex Carbohydrates •  Chains of three or more sugar molecules –  Oligosaccharides •  3-­‐10 sugar molecules •  Examples sources: dried beans, peas, and len]ls –  Polysaccharides •  Long chains of monosaccharides •  Structural differences affect how they behave in water and with hea]ng •  Diges]ble (e.g. starch) or nondiges]ble (e.g. fiber) Complex Carbohydrates •  Starch – Storage form of energy in plants – Found in grains, legumes, and tubers (potatoes and yams) – Long chains of glucose units •  Amylose—straight chains •  Amylopec:n—branched chains – Digested more rapidly than amylose – Resistant starch: A starch that is not digested 4 2/16/16 Complex Carbohydrates •  Glycogen – Storage form of carbohydrates in animals – Highly branched chains of glucose units – Blood glucose – Most stored in our skeletal muscle and liver – Carbohydrate “loading” Complex Carbohydrates •  Fiber – Nondiges]ble carbohydrates and lignins – Dietary fiber: soluble + insoluble fiber •  Fruits, vegetables, legumes, and whole grains – Func:onal fiber: Isolated and added to foods – Total fiber: Sum of dietary fiber and func]onal fiber Types of Dietary Fiber Soluble •  Dissolves in water à gel-­‐
like à slows diges]on, lowers blood cholesterol and glucose levels •  Fermentable •  Example: Fruits, vegetables, legumes, oats, oat bran, legumes (dried beans and peas) Insoluble •  Does not dissolve in water à creates a bulk à larger, so`er stool •  Fermentable (Resistant Starch) vs. Non-­‐fermentable •  Example: Bran por]on of whole grains, skins of fruits/
vegetables, cauliflower, potato skins 5 2/16/16 Complex Carbohydrates (Dietary Fiber) •  Gums and mucilages –  Gums: Gel-­‐forming fibers in plant cell walls and seeds –  Mucilages: gela]nous soluble fiber found in seaweed •  Pec:ns –  “Sugar acids”; keeps fruits in shape –  Dietary fiber found in all plants, especially fruits and berries –  Pec]ns + acid + sugar = jam Complex Carbohydrates (Dietary Fiber) Complex Carbohydrates (Dietary Fiber) •  Beta-­‐glucans –  Polysaccharides of branched glucose units linked with beta glycosidic bonds –  Found in barley and oats –  Help decrease blood cholesterol levels •  Lignin: –  Non actually carbohydrates; composed of mul]-­‐
ring alcohol units that compose the only non-­‐
carbohydrate component of dietary fiber –  Found in cell walls of woody plants and the seeds of fruits Dietary Fiber •  Cellulose: long, straight chains of glucose molecules with beta glycosidic bonds – Structural func]on in plants: forms the woody fibers in trees and strong plant cell walls •  Hemicelluloses: variety of monosaccharides with many branching side chains – Usually mixed with cellulose in plants – Outer bran layer in cereal grains, legumes, vegetables, nuts 6 2/16/16 Carbohydrate Diges]on •  Diges]on breaks down carbohydrates to single sugars – Mouth •  Salivary amylase – Stomach •  HCl’s acidity stops the ac]on of salivary amylase à stops carbohydrate diges]on Carbohydrate Diges]on •  Diges]on – Small intes]ne •  Pancrea:c amylase con]nues starch diges]on •  Brush border enzymes digest disaccharides •  Other diges]ve enzymes: – Maltase, sucrase, and lactase Carbohydrate Diges]on •  Diges]on – Bonds that link glucose molecules •  Alpha bonds – Broken down by human enzymes (e.g. starch) •  Beta bonds – Bonds remain unbroken by human enzymes (e.g. cellulose, resistant starch) 7 2/16/16 Carbohydrate Absorp]on •  Absorp]on in the small intes]ne – Glucose, galactose, fructose molecules travel to the liver through the portal vein – Liver converts the absorbed monosaccharaides to glucose: •  Galactose à glucose •  Fructose à glucose Carbohydrates and Glucose in the Body •  Excess glucose is stored as… – Liver glycogen (~1/3) •  Maintains normal blood glucose levels – Muscle glycogen (~2/3) •  Fuels muscle ac]vity Carbohydrates and Glucose in the Body •  Glucose is our primary fuel – To drive chemical processes – To maintain normal blood glucose levels •  Other sources of energy: fat, protein •  What is the order of energy usage by body? 8 2/16/16 Consequence of Low Blood Sugar •  Sparing body protein – Adequate carbohydrates prevent body from making glucose from body proteins – Preven]ng ketosis •  Ketone bodies à ketosis à dehydra]on •  Body needs a minimum of 50 to 100 grams of carbohydrate/day to prevent ketosis Carbohydrates and Glucose in the Body •  Regula]ng blood glucose – Hyperglycemia vs. Hypoglycemia – Controlled by hormones: •  Insulin •  Glucagon •  Epinephrine (Adrenaline) – “Fight-­‐or-­‐flight” hormone Regula]ng Blood Glucose •  Glycemic Index measures effect of food on blood glucose levels – Different foods vary in their effect on blood glucose levels – Foods with High Glycemic Index cause faster and higher rise in blood glucose 9 2/16/16 Glycemic Index High Blood Glucose: Diabetes Mellitus •  What is diabetes? •  Normally: •  Eat food with glucose à blood and cells •  If too much blood glucose à pancreas releases insulin à blood glucose decreases – If you have diabetes: •  Pancreas: liqle or no insulin OR cells do not respond appropriately to insulin à hyperglycemia High Blood Glucose: Diabetes •  Forms of diabetes mellitus: – Diabetes Type I: – Diabetes Type II: – Gesta:onal diabetes: The Role of Carbohydrates in Our Diet •  Cons: excess simple sugar à weight gain, poor nutrient intake, tooth decay •  Pros: high intake of foods rich in dietary fiber offers many health benefits, including reduced risk of: –  Obesity –  Type 2 diabetes –  Cardiovascular disease –  Gastrointes]nal disorders •  Increase fiber intake gradually while drinking plenty of fluids 10 2/16/16 Carbohydrates and Health •  Fiber and obesity – Possible role in weight control •  Fiber and type 2 diabetes – Beqer control of blood glucose •  Fiber and cardiovascular disease – Can lower blood cholesterol levels •  Fiber and gastrointes:nal disorders – Healthier gastrointes]nal func]oning Carbohydrates and Health •  Modera]ng sugar intake – Use less added sugar – Limit so` drinks, sugary cereals, candy, ice cream, and sweet desserts – Choose fresh fruits or those canned in water Carbohydrates and Health •  Nega]ve effects of excess fiber: – If add supplemental fiber too quickly, may have side effects: abdominal bloa]ng, gas – Can bind small amounts of minerals à prevent some mineral absorp]on •  Examples: Zinc, Calcium, Iron •  Fiber does not have UL: because ea]ng a lot of fiber (found naturally in foods) doesn’t really affect overall health of healthy people. The Role of Carbohydrates in Our Diet •  Choosing Carbohydrates Wisely – Increase fruit, vegetables, whole grains, low-­‐fat milk •  Strategies – Eat peel fruit/vegetables – Eat legumes – Choose brown rice – Choose high-­‐fiber cereal – Drink plenty of water! 11 2/16/16 Carbohydrates and Health •  Nutri:ve sweeteners: – Monosaccharides, disaccharides, and sugar alcohols – Natural vs. refined •  Non-­‐nutri:ve sweeteners: – Saccharin – Aspartame – Acesulfame K – Sucralose Nutri]ve Sweeteners Nutri:ve Sweeteners: substances that sweeten food and can absorbed and yield energy in the body. •  Types: 1.  Natural: mono + di-­‐saccharides •  e.g. honey, maple syrup 2.  Refined: mono + di-­‐saccharides extracted from plant food •  e.g. white sugar, fructose 3.  Sugar Alcohol/Polyols: may be sugar/sucrose free, but not always calorie free •  e.g. xylitol • 
Non-­‐Nutri]ve Sweeteners •  Non-­‐nutri:ve sweeteners: “ar]ficial sweeteners”; yields almost no energy •  Types: 1.  Saccharin (1970s; bladder cancer) 2.  Aspartame (phenylalanine + aspar]c acid; PKU) 3.  Acesulfame K (stable under heat) 4.  Sucralose (used in baked goods, beverages, gela]n, etc.) 12