Carbohydrates Capture Energy from the Sun Sugars, starches, and fibers Major food sources: plants Produced during photosynthesis Two main carbohydrate types Simple Complex Photo © PhotoDisc 1

Monomers of carbohydrates Example Hexose sugars (the hexoses shown (a) Monosaccharides Monomers of carbohydrates Example Hexose sugars (the hexoses shown here are isomers) Example Pentose sugars Glucose Fructose Galactose Deoxyribose Ribose Figure 2.15a

Monosaccharides Glucose Most abundant (dextrose) Medium flavor Usually joined to another sugar Energy for body cells Blood sugar Found in fruits, vegetables, honey Photo © AbleStock 3

Monosaccharides Fructose Fruit sugar Tastes sweetest Found in fruits, honey, and corn syrup Photo © Photodisc 4

Monosaccharides Galactose Bond to glucose - lactose Primary sugar in milk and dairy products Photo © AbleStock 5

Disaccharides: The Double Sugars 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 6

Disaccharides: The Double Sugars Maltose: glucose + glucose “Malt sugar” Seldom occurs naturally Product of starch breakdown Found in germinating cereal grains

Complex Carbohydrates Oligosaccharides Three to ten sugar molecules Beans, peas, and lentils Polysaccharides Long chains of glucose Structural differences Digestible or nondigestible 8

Complex Carbohydrates Starch Long chains of glucose Amylose—straight chains Amylopectin—branched chains Resistant starch Not digested Glycogen Stored skeletal muscle and liver 9

Complex Carbohydrates Fiber Nondigestible carbs and lignins Dietary fiber: found in plants Fruits, vegetables, legumes, and whole grains Functional: isolated and added to foods Total:sum of dietary and functional fiber 10

Complex Carbohydrates Types of fiber Cellulose Grains, fruit, vegetables, and nuts Hemicellulose Variety of monosaccharides with many branching side chains 11

Complex Carbohydrates Pectins Especially fruits Gums and cilages Gel-forming fibers Lignins Nondigestable 12

Complex Carbohydrates Beta-glucans Branched polysaccharides Barley and oats Helps decrease blood cholesterol Chitin and chitosan Primarily consumed in supplement form Marked as weight-loss supplements May impair absorption of fat-soluble vitamins and some minerals 13

Digestion and Absorption Mouth Salivary amylase begins digestion Stomach Acidity of stomach juices halt action of salivary amylase 14

Digestion and Absorption Small intestine Pancreatic amylase Brush border enzymes digest disaccharides Other enzymes Maltase, sucrase, and lactase 15

Digestion and Absorption Enzymes Highly specific Examples: lactase & Beano Some carbs remain intact; fiber and resistant starch 16

+ + + Figure 2.14 (a) Dehydration synthesis Monomers are joined by removal of OH from one monomer and removal of H from the other at the site of bond formation. + Monomer 1 Monomer 2 Monomers linked by covalent bond (b) Hydrolysis Monomers are released by the addition of a water molecule, adding OH to one monomer and H to the other. + Monomer 1 Monomer 2 Monomers linked by covalent bond (c) Example reactions Dehydration synthesis of sucrose and its breakdown by hydrolysis Water is released + Water is consumed Glucose Fructose Sucrose Figure 2.14

Digestion and Absorption 18

Carbohydrates in the Body Glucose primary fuel Glucose needed to burn fat efficiently Maintain blood glucose Excess glucose is stored Using glucose for energy Liver glycogen (1/3) Maintain normal blood glucose Muscle glycogen (2/3) Muscle activity 19

Carbohydrates in Action Using glucose for energy Sparing body protein Adequate carbs prevent body from making glucose from proteins Preventing ketosis Ketone bodies  ketosis  dehydration Body needs a min of 50 to 100 g of carbo/d to prevent

Carbohydrates in Action Regulating blood glucose Controlled by hormones Insulin Key Glucagon Breaks down glycogen to glucose Epinephrine “Fight or flight” hormone 21

Carbohydrates in Action Regulating blood glucose Glycemic index Different foods vary in their effect on blood glucose Measure effect of food on blood glucose

Carbohydrates in Action: Regulating Blood Glucose 23

High Blood Glucose: Diabetes Mellitus What is diabetes? Disorder of total energy metabolism After dig, glucose into blood and to cells Requires insulin Hyperglycemia: high blood glucose Glucose unable to enter cells Increased risk of high BP, heart and kidney disease

High Blood Glucose: Diabetes Mellitus Consequences Hyperglycemia “Starvation in the midst of plenty” Lose access to its main source of fuel Use of fat and protein for energy sources  ketosis and acidosis Over time, damage to body proteins and tissues 25

High Blood Glucose: Diabetes Mellitus Forms of diabetes mellitus Type 1 diabetes: lack of insulin production Type 2 diabetes: cells resistant to insulin Prediabetes Gestational diabetes: occurs during pregnancy 26

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Hypoglycemia Symptoms Nervousness, irritability, hunger, headache, shakiness, rapid heart rate, and weakness Results from Too much insulin, missed meals, and vigorous exercise Reactive hypoglycemia Fasting hypoglycemia 28

Carbohydrates in Your Diet Recommended carbohydrate intake RDA = 130 grams per day AMDR = 45–65% of calories Daily Value (for 2,000 kcal) = 300 grams Dietary Guidelines “Reduce intake of added sugars” < 25% of daily energy intake Choose whole grains, vegetables, fruits, beans and peas > ½ of all grains as whole grains 29

Carbohydrates in Your Diet Current consumption How much are we eating? AMDR = 45–65% of kcal Average American adult = 49–50% of kcal 13% of population has added sugar intake > 25% of kcal Soft drinks! At the same time, milk consumption and vitamin and mineral quality of diet is declining

Carbohydrates in Your Diet Choosing carbs wisely Increase fruit, vegetables, whole grains, low-fat milk Strategies Eat peel of fruit/vegetables Eat legumes Choose brown rice Choose high-fiber cereal Gradually increase and drink plenty of water! 31

Carbohydrates in Your Diet Nutritive sweeteners Natural vs. refined Non-nutritive sweeteners Saccharin Aspartame Acesulfame K Sucralose 32

Carbohydrates and Health Sugar and dental caries promoted by: Carb remaining in the mouth Food that sticks to teeth Frequent consumption Sip high sugar drinks over time Photo @ PhotoDisc 33

Carbohydrates and Health Fiber and obesity ? Fiber and type 2 diabetes Fiber and cardiovascular disease Fiber and gastrointestinal disorders 34

Carbohydrates and Health Negative effects of excess fiber Constipation? Gas and bloating? Can bind small amounts of minerals