chapter4 &carbohydrates:&simple&sugars&and&...

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Chapter 4 Carbohydrates: Simple Sugars and

Complex Chains BIOL 103

What Are Carbohydrates?

•  Sugars, starches, and fibers •  Major food sources: Plants – Produced during photosynthesis

•  Two main carbohydrate types – Simple – Complex

Simple Sugars

•  Monosaccharides – Glucose – Fructose – Galactose

Monosaccharides

•  Glucose/Dextrose – Most ___________ 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

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Monosaccharides

•  Fructose/Levulose –  “__________________” –  Tastes the _________ of all the sugars

–  Occurs naturally in fruits and vegetables

–  Found in fruits, vegetables, honey, and corn syrup

High Fructose 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

Why is High Fructose Corn Syrup associated with weight gain?

1.  Cheap corn à supersize 2.  Fructose does not release ______ à less _____ produc[on à eat more à fat produc[on •  Compared to glucose, fructose is preferen[ally metabolized to lipid in the liver.

•  However, note that overconsump[on of ANY forms of sugar will contribute to weight gain.

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Monosaccharides

•  Galactose –  Rarely occurs as a monosaccharide in food

–  Usually bonds to glucose to form ____________

Simple Sugars

•  Disaccharides: Consist of two monosaccharides linked together – Sucrose: glu + fru – Lactose: glu + gal – Maltose: glu + glu

•  Linked by ______________ bonds

Disaccharides

•  Sucrose: glucose + fructose –  “__________________” – Made from sugar cane and sugar beets

–  Listed as sugar on food labels •  Lactose: glucose + galactose –  “__________________” –  Found in milk and milk products

Lactose Intolerance

•  Who has it? – Anyone who does not have enough ___________

•  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

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Disaccharides

•  Maltose: glucose + glucose – ___________________ – 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 or non-‐diges[ble

Complex Carbohydrates •  Starch

–  Storage form of energy in __________________

–  Found in grains, legumes, and tubers

–  Long chains of glucose units •  Amylose •  AmylopecCn

– Digested more rapidly than amylose

–  Resistant starch: A starch that is not digested

Complex Carbohydrates

•  Glycogen – Storage form of carbohydrates in ______

– Highly branched chains of glucose units

– Blood glucose – Most stored in our ________ and ________

– Carbohydrate “loading”

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Complex Carbohydrates

•  Fiber – Non-‐diges[ble carbohydrates and lignins – Dietary fiber: soluble + insoluble fiber • Fruits, vegetables, legumes, and whole grains

– FuncConal 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

•  Fermentable •  Example: Fruits, vegetables,

legumes, oats, oat bran, legumes (dried beans and peas)

Insoluble •  Does not dissolve in water

•  Fermentable vs. Non-‐

fermentable •  Example: Bran por[on of

whole grains, skins of fruits/vegetables, cauliflower, potato skins

Dietary Fiber

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Review Ques[ons

1.  What is the difference between starch and glycogen?

2.  What is the difference between starch and fiber in terms of diges[on in the human body?

3.  What is HFCS 65 made up of? 4.  In your own words, why is consuming high fructose

corn syrup associated with weight gain? 5.  What are the health benefits of consuming soluble

fiber? How about for insoluble fiber?

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


•  Diges[on – Small intes[ne • PancreaCc amylase con[nues starch diges[on • Brush border enzymes digests disaccharides • Other diges[ve enzymes: – Maltase, sucrase, and lactase


•  Diges[on – Bonds that link glucose molecules • Alpha bonds – starch

• Beta bonds – cellulose/fiber, resistant starch

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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) – Muscle glycogen (~2/3)

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•  Glucose is our primary fuel 1.  To drive chemical processes 2.  To maintain normal blood glucose levels

•  Other sources of energy: •  What is the order of energy usage by body?

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


•  Regula[ng blood glucose – Hyperglycemia vs. Hypoglycemia

Blood Glucose (FasCng)

Blood glucose (2 hrs aOer meal)

Normal 70-‐99 mg/dL <140 mg/dL

Hyperglycemia >126 mg/dL >200 mg/dL

Hypoglycemia <72 mg/dL N/A


•  Regula[ng blood glucose – Controlled by hormones: •  Insulin: • Glucagon: • Epinephrine (Adrenaline): – “Fight-‐or-‐flight” hormone

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Regula[ng Blood Glucose

•  Glycemic Index measures effect of food on blood ________________ levels

– Different foods vary in their effect on blood glucose levels

– Foods with ______ Glycemic Index cause faster and higher rise in blood glucose

Glycemic Index High Blood Glucose: Diabetes Mellitus

•  What is diabetes? •  A chronic disease in which the body’s ability to produce or respond to insulin is impaired, resul[ng in prolonged high blood sugar

•  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:

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High Blood Glucose: Diabetes

•  Forms of diabetes mellitus: – Diabetes Type I:

– Diabetes Type II:

– GestaConal diabetes: Postprandial (1-‐2 hrs aOer eaCng) Blood Sugar Measurements •  Normal: postprandial blood glucose <140 mg/dL •  Diabe[cs: postprandial blood glucose is >200mg/dL •  Pre-‐diabe[c: postprandial blood glucose 140mg/dL-‐200mg/dL

Consequences of hypo/hyperglycemia

•  Severe hypoglycemia •  Ketosis, ketoacidosis •  Coma, death

•  Short-‐term hyperglycemia •  Ketosis, ketoacidosis (more common in type-‐I)

•  Long-‐term hyperglycemia •  Diabetes complica[ons – damages to nerves, blood vessels, and thus, result in impaired func[ons of our organs

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

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Carbohydrates and Health

•  Fiber and obesity – Possible role in weight control

•  Fiber and type 2 diabetes – Berer control of blood glucose

•  Fiber and cardiovascular disease – Can lower blood cholesterol levels

•  Fiber and gastrointesCnal disorders – Healthier gastrointes[nal func[oning


•  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.


•  Modera[ng sugar intake • Use less added sugar • Limit sot drinks, sugary cereals, candy, ice cream, and sweet desserts • Choose fresh fruits or those canned in water

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!

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•  NutriCve sweeteners: – Monosaccharides, disaccharides, and sugar alcohols – Natural vs. refined

•  Non-‐nutriCve sweeteners: – Saccharin – Aspartame – Acesulfame K – Sucralose

Nutri[ve Sweeteners NutriCve Sweeteners:

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, and low in calories. e.g. xylitol, mannitol, sorbitol

Sugar-‐Free Candies

•  MalCtol = sugar alcohol –  From plants –  Benefits:

•  No tooth decay •  Nearly as sweet as sugar à “I can eat more”

•  Laxa[ve effect: –  15 gummy bears (40g) = 1 dose

Non-‐Nutri[ve Sweeteners •  Non-‐nutriCve 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.)

•  Saccharin: Sweet’N Low •  Aspartame: NutraSweet, Equal •  Acesulfame K: Sweet One, Sunere •  Sucralose: Splenda

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