Ch. 19 Carbohydrates

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Ch. 19Carbohydrates

• Milbank High School

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Chapter Objectives

• 1.What are carbohydrates? What is the difference
  between mono-, di-, and polysaccharides?
• 2.What are the structures of the most commonly
  occurring monosaccharides? Be able to classify
  them as aldoses or ketoses and as trioses,
  pentoses, or hexoses.
• 3.What is the difference between a D and an L
  sugar?

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Chapter Objectives

• 4.What is mutarotation? How does it occur?
• 5.What are the structures of sucrose, lactose,
  and maltose, the most common disaccharides? What
  monosaccharides make up each of these
  disaccharides?
• 6.Compare and contrast starch, glycogen, and
  cellulose.

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What is Biochemistry?

• The chemistry of molecules and reactions found in
  living organisms

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Carbohydrates

• Carbon hydrates
• Compounds containing carbon, hydrogen, and oxygen
• Starches and fibers (complex carbohydrates)
• Sugars
• Cellulose
• Contain hydroxyl groups
• And either an aldehyde or ketone
• Known as polyhydroxy aldehydes or ketones

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Monosaccharides

• Simple carbohydrates
• Cannot be further hydrolyzed
• Contain 3-7 carbons
• Readily dissolve in water
• Can link together to form more complex
  carbohydrates
• Disaccharides
• Trisaccharides
• Polysaccharides

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Sec. 19.1General Terminology and Stereochemistry

• Named using IUPAC to name monosaccarides
• Name the number of carbons, then add -ose
• Trios, tetrose, pentose, hexose etc
• If aldehyde is attached aldotetrose
• If ketone is attached ketotetrose

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Common monosaccharides

• Glucose
• Fructose

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Enantiomers

• Molecules that are nonsuperimposable mirror
  images of each other
• Have identical physical properties except one
• They rotate plane-polarized light in opposite
  directions

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Trioses

• Simplest sugars
• Two enantiomers
• D sugars
• L sugars

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Sec. 19.2Hexoses

• Aldohexoses
• 16 isomers (8 enantiomeric pairs)
• 3 most common
• Glucose, mannose, galactose
• Ketohexoses
• 8 isomers
• fructose

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Glucose

• Most abundant sugar in nature
• Fruits
• grape sugar
• Dextrose b/c it is dextrorotatory
• Carbs converted to glucose
• Produces energy for our cells
• Circulating carbohydrate
• Blood sugar

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Glucose Cont

• Synthetically made by the hydrolysis of starch
• Corn starch
• corn sugar

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Mannose

• Component of polysaccharide mannan
• Berries
• Vegetable ivory endosperm
• Differs from glucose at only one point

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Galactose

• Needed by human body for synthesis of lactose
• In mammary glands
• Also important constituent of the glycolipids
• Occur in brain in myelin sheath of nerve cells
• brain sugar
• Differs from glucose at only one point

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Fructose

• Only naturally occurring ketohexose
• Also similar structure to that of glucose
• Found in honey (40)
• Formed in prostate gland
• Energy source for spermatozoa

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Artificial Sweeteners

• High-intensity sweeteners
• Manufactured in place of mono- and disaccharides
• Saccharin
• 1890s
• 500-700 times sweeter than sucrose
• Carcinogenic

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Artificial Sweeteners

• Aspartame
• 1967
• 160 times sweeter than sucrose
• Used in diet soda
• Sucralose
• 1998
• 600 times sweeter than sucrose
• Passes through body unchanged

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Sec. 19.3Cyclic Structures of Monosaccharides
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Sec. 19.4Properties of Monosaccharides

• Crystalline solids at room temperature
• Quite soluble in water
• Converted to anions when Tollens and Benedicts
  reagents are used
• Used in simple and rapid diagnostic tests for the
  presence of glucose in blood or urine

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Sec. 19.5 Disaccharides
                                                                                                                                                                 

• Composed of two monosaccharide units
• Joined when one monosaccharide reacts with the
  hydroxyl group of a second monosaccharide
• Forms a carbon-oxygen-carbon linkage
• glycosidic linkage

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Maltose

• Occurs in sprouting grain
• Forms malt in the manufacture of beer
• malt sugar
• About 30 as sweet as sucrose
• Body cant utilize it directly
• Must be broken down by enzymes

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Lactose

• Milk sugar
• Occurs in the milk of humans, cows, and other
  mammals
• Human milk 7.5 lactose
• Cows milk 4.5 lactose
• Synthesized only by mammary tissue in nature
• Commercial produced from whey (from cheese)
• 1/6th as sweet as sucrose

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Lactose Intolerance

• People are unable to digest lactose in milk
• Need lactase in small intestine to digest it
  properly
• Up to 20 of US population suffer some degree of
  lactose intolerance
• Produces bacteria in colon if not broken down
  properly
• Leads to abdominal distension, cramps, diarrhea

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Lactose Intolerance Cont

• Foods can be treated with lactase
• Lactaid
• Tablets taken orally with dairy foods to assist
  in their digestion

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Sucrose

• Beet sugar, cane sugar, table sugar, or just
  sugar
• Largest selling pure organic compound in the
  world
• Obtained from sugar canes and beets
• Average American 100 pounds of sucrose every
  year

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Sucrose Cont

• May cause cancer, heart disease, migraine
  headaches, hyperactivity in children, obesity,
  and tooth decay

                                                                                                                                   
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Sec. 19.6Polysaccharides

• Most abundant carbs in nature
• Store energy and make up plant cells
• High-molar mass
• Starch, glycogen, and cellulose

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Starch

• Most important source of carbs in the human diet
• More than 50 of our carb intake
• Granule form
• Storage
• Potatoes 15
• Wheat 55
• Corn 65
• Rice 75

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Starch Cont

• Mixture of amylose and amylopectin
• Amylose 60-300 glucose units per chain
• Amylopectin 300-6000 glucose units
• Commercial starch
• White powder
• Stamps, envelopes, labels (sticky upon wetting)

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Glycogen

• animal starch
• Reserve carb of animals
• All mammalian cells contain glycogen
• Liver and skeletal cells the most
• Used when fasting

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Cellulose

• Fibrous carb found in all plants
• Cell walls
• Most abundant of all carbs
• Makes up 50 of all carbon in the vegetable world
• Much hydrogen bondinginsoluble in water

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Cellulose Cont

• Cant be digested by humans
• Herbivores contain special enzymes to digest it
  and use it for energy
• Termites

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Dietary Fiber

• Insoluble fiber (cellulose)
• Reduces risk of colon cancer and heart disease
  (reduces cholesterol)
• ADA recommends 20-35 g a day
• Most Americans get 14-15 g a day