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Published byCollin Simpson Modified over 9 years ago
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Carbohydrates: Simple Sugars and Complex Chains Chapter 5
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Carbohydrates all plant food milk carbohydrates are not equal
simple carbohydrates complex carbohydrates
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Carbohydrates Sugars, starches, and fibers Major food sources: plants
Produced during photosynthesis Two main carbohydrate types Simple and complex Photo © PhotoDisc 3
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Simple Carbohydrates sugars monosaccharides – single sugars
disaccharides – 2 monosaccharides
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Simple Sugars: Monosaccharides and Disaccharides
Simple carbohydrates Monosaccharides Glucose Fructose Galactose Disaccharides Sucrose Lactose Maltose 5
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Simple Carbs monosaccharides all are 6 carbon hexes
6 carbons 12 hydrogens 6 oxygens arrangement differs accounts for varying sweetness glucose, fructose, galactose
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Monosaccharides Glucose Is most abundant Also is called dextrose
Gives food sweet flavor Provides energy to body cells Blood sugar Found in fruits, vegetables, honey © AbleStock 7
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Monosaccharides Fructose Also called levulose or fruit sugar
Tastes the sweetest Occurs naturally in fruits and vegetables Found in fruits, honey, and corn syrup © Photodisc 8
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Monosaccharides Galactose Primary sugar in milk and dairy products
Rarely found naturally As a single sugar - Hardly even taste sweet © AbleStock 9
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Disaccharides: The Double Sugars
Two monosaccharides linked together Sucrose, lactose, and maltose 10
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Disaccharides pairs of the monosaccharides glucose is always present
2nd of the pair could be fructose, galactose or another glucose taken apart by hydrolysis put together by condensation hydrolysis and condensation occur with all energy nutrients maltose, sucrose, lactose
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Condensation making a disaccharide
chemical reaction linking 2 monosaccharides
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Hydrolysis breaking a disaccharide water molecule splits
occurs during digestion
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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 14
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Sucrose fructose and glucose tastes sweet
fruit, vegetables, grains table sugar is refined sugarcane and sugar beets brown, white, powdered
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Lactose glucose and galactose main carbohydrate in milk
known as milk sugar
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Lactose Intolerance age, damage, medication, diarrhea, malnutrition
management requires dietary change 6 grams (1/2 cup) usually tolerable take in gradually hard cheeses & cottage cheese enzyme drops or tablets lactose free diet is extremely difficult to accomplish
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Disaccharides: The Double Sugars
Maltose: glucose + glucose Product of starch breakdown Found in germinating cereal grains Not abundant
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Complex Carbohydrates
starches and fibers polysaccharides chains of monosaccharides
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Complex Carbohydrates
Chains of two or more sugar molecules Oligosaccharides Polysaccharides Structural differences Digestible or nondigestable 21
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Complex Carbohydrates
Starch How plants store energy Found in grains, legumes, and tubers Long chains of glucose units Amylose—straight chains Amylopectin—branched chains Resistant starch 22
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Starches stored in plant cells body hydrolyzes plant starch to glucose
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Complex Carbohydrates
Glycogen Body’s storage form of carbohydrate Provides glucose when blood glucose levels get low Highly branched chains of glucose units Most stored in our skeletal muscle and liver Carbohydrate “loading” 24
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Glycogen limited in meat and not found in plants BUT
not an important dietary source of carbohydrate BUT all glucose is stored as glycogen long chains allow for hydrolysis and release of energy
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Complex Carbohydrates
Fiber Indigestible chains of monosaccharides Dietary fiber: found in plants Fruits, vegetables, legumes, and whole grains Functional fiber: isolated and added to foods 26
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Fiber structural parts of plants
found in all plant derived food bonds of fibers cannot be broken down during the digestive process minimal or no energy available
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Complex Carbohydrates
Types of fiber Oligosaccharides: short chains of monosaccharides Raffinose, stachyose Dried beans, peas, lentils, human milk Cellulose In plants: grains, fruit, nuts, vegetables Hemicellulose Variety of monosaccharides 28
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Complex Carbohydrates
Pectins All plants, especially fruits Gums and cilages Gel-forming fibers that hold plant cells together Lignins Nondigestable substances in vegetables and fruit 29
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Fiber types pectins lignins resistant starches cellulose
classified as fibers escape digestion and absorption
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Fiber Characteristics
soluble fibers, viscous, fermentable easily digested by bacteria in colon associated with protection against heart disease and diabetes lower cholesterol and glucose levels found in legumes and fruits
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Fiber insoluble and not easily fermented promote bowel movements
alleviate constipation found in grains and vegetables
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Carbohydrate Digestion
break down into glucose body is able to absorb and use large starch molecules extensive breakdown disaccharides broken once monosaccharides don’t need to be broken down
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Carbohydrate Digestion and Absorption
Digestion: breaking down carbohydrates into simple sugars Begins in the Mouth – Chewing releases saliva Salivary amylase begins digestion of carbohydrates Stomach No carbohydrate digestion 35
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Carbohydrate Digestion and Absorption
Small intestine Pancreatic amylase continues starch digestion The brush border enzymes digest disaccharides Other digestive enzymes Maltose, sucrose, and lactase 36
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small intestine majority of carbohydrate digestion takes place here
pancreatic amylase reduces carbs to glucose chains or disaccharides specific enzymes finish the job maltase maltose into 2 glucose sucrase sucrose into glucose and fructose lactase lactose into glucose and galactose
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large intestine 1-4 hours for sugars and starches to be digested
only fibers remain attract water, which softens stool bacteria ferment some fibers water, gas, short-chain fatty acids (used for energy)
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Carbohydrate Digestion and Absorption
Absorption: The small intestine swings into action End products of carbohydrate digestion Glucose Galactose glucose Fructose glucose Liver stores and releases glucose To maintain blood glucose levels 39
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Carbohydrate Digestion and Absorption
Travels with carbohydrate 40
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Carbohydrates glucose provides energy for the brain and ½ of energy for muscles and tissues glycogen is stored glucose glucose is immediate energy glycogen is reserve energy
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Carbohydrates in Action
Glucose is our primary fuel Maintain normal blood glucose levels Excess glucose is stored Using glucose for energy Stored glucose as glycogen Liver Muscle 42
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Carbohydrate Metabolism
1/3 of body’s glycogen is stored in liver released as glucose to bloodstream eat – intake glucose liver condenses extra glucose to glycogen blood glucose falls liver hydrolyzes glycogen to glucose Glycogen is bulky, so we store only so much: short term energy supply Fat is the long term energy supply.
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Glucose for Energy enzymes break apart glucose – yielding energy
inadequate supply of carbohydrates ketone bodies (fat fragments) are an alternate energy source during starvation excess ketones can lead to ketosis: imbalance of acids in body minimum of 50 – 100 grams of carbs/day are needed to avoid ketosis
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Carbohydrates in Action
Using glucose for energy Sparing body protein Adequate carbohydrates spare protein Preventing ketosis Ketone bodies Ketosis dehydration
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Glucose Homeostasis maintaining an even balance of glucose is controlled by insulin and glucagon insulin moves glucose into the blood glucagon brings glucose out of storage
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Carbohydrates in Action
Regulating blood glucose Why? To maintain supply for cells Controlled by hormones Insulin Key Glucagon Breaks down glycogen Epinephrine “Fight or flight” hormone Glycemic index 47
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Maintaining Blood Glucose Homeostasis
1 Intestine Maintaining Blood Glucose Homeostasis When a person eats, blood glucose rises. 2 Pancreas High blood glucose stimulates the pancreas to release insulin. Insulin 3 Insulin stimulates the uptake of glucose into cells and storage as glycogen in the liver and muscles. Insulin also stimulates the conversion of excess glucose into fat for storage. Liver Fat cell Muscle 4 As the body's cells use glucose, blood levels decline. 5 Pancreas Low blood glucose stimulates the pancreas to release glucagon into the bloodstream. Glucagon 6 Glucagon stimulates liver cells to break down glycogen and release glucose into the blood.a Glucose Insulin Glucagon Glycogen Liver a The stress hormone epinephrine and other hormones also bring glucose out of storage. 7 Blood glucose begins to rise.
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Carbohydrates in Action: Regulating Blood Glucose
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Carbohydrates in Action
Diabetes mellitus Consequences Hyperglycemia—persistent high blood glucose levels Glucose unable to enter cells Increased risk of high blood pressure, heart disease, and kidney disease Damage to body proteins and tissues 50
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Carbohydrates in Action
Diabetes mellitus Type 1 diabetes: lack of insulin production Type 2 diabetes: cells are resistant to insulin Prediabetes Insulin resistance Gestational diabetes: occurs during pregnancy 51
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Carbohydrates in Action
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Carbohydrates in Action
Diabetes Best prevention Healthful diet Monitoring and well-balanced meals The Exchange List for Meal Planning Regular exercise 53
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Sugar ½ comes from natural sources, ½ from refined and added
sucrose, corn syrup, honey excess can lead to nutrient deficiencies and tooth decay empty calories sugar and starch break down in the mouth
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Sugar recommended intake
added sugar = no more than 10% of energy intake
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Carbohydrates in Action
Low blood glucose: 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 56
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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 Choose carbohydrates wisely Choose fiber-rich fruits, vegetables, and whole grains often 57
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Carbohydrates in Your Diet
Choosing carbohydrates 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! 58
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Starch and Fiber diet that includes starch, fiber and natural sugars
whole grains, vegetables, legumes, fruits may protect against heart disease and stroke reduces the risk of type 2 diabetes enhances the health of the large intestine can promote weight loss
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Carbohydrates in Your Diet
Moderating sugar intake Use less added sugar Limit soft drinks, sugary cereals, and candy Choose fresh fruits or those canned in water or juice Photo © CSquared Studios/PhotoDisc 60
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Carbohydrates in Your Diet
Nutritive sweeteners Natural vs. refined Sugar alcohols Non-nutritive sweeteners Saccharin Aspartame Acesulfame K Sucralose 61
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Artificial Sweeteners
help keep sugar and energy intake down anything we eat has FDA approval saccharin aspartame acesulfame potassium sucralose neotame
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Carbohydrates and Health
Sugar High sugar intake may be low in nutrients High sugar intake promotes tooth decay PhotoDisc 64
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Sugar Replacers sugar alcohols provide bulk and sweetness
cookies, gum, candy, jelly do contain minimal kcal low glycemic response absorbed slowly do not cause dental caries
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Carbohydrates and Health
Fiber Possible role in weight control Better control of blood glucose Reduced risk of heart disease Healthier gastrointestinal functioning Negative effects of excess fiber Gradual intake and increased water consumption Can bind small amounts of minerals 66
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