1. 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

2. 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

3. 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

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

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

6. 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

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

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

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

10. 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

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

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

13. 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

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

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

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

17. + + + 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

18. Digestion and Absorption18

19. 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

20. 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

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

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

23. Carbohydrates in Action: Regulating Blood Glucose23

24. 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

25. 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

26. 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

27. 27

28. 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

29. 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

30. 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

31. 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

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

33. 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
PhotoDisc 33

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

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