Carbohydrates - Chemistry

Carbohydrates - Chemistry

Carbohydrates CHEM 2030 Carbohydrates polyhydroxyaldehydes or polyhydroxy-ketones of formula (CH2O)n, or compounds that can be hydrolyzed to them. (aka sugars or saccharides) Monosaccharides carbohydrates that cannot be hydrolyzed to simpler carbohydrates; eg. Glucose or fructose. Disaccharides carbohydrates that can be hydrolyzed into two monosaccharide units; eg. Sucrose, which is hydrolyzed into glucose and fructose. Oligosaccharides carbohydrates that can be hydrolyzed into a few monosaccharide units. Polysaccharides carbohydrates that are are Aldose polyhydroxyaldehyde, eg glucose Ketose polyhydroxyketone, eg fructose Triose, tetrose, pentose, hexose, etc.

carbohydrates that contain three, four, five, six, etc. carbons per molecule (usually five or six); eg. Aldohexose, ketopentose, etc. Epimers stereoisomers that differ only in configuration about one chiral center. H HO H H CHO OH H OH OH CH2OH D-glucose

HO HO H H CHO H H OH OH CH2OH D-mannose epimers glyceraldehyde an aldotriose CHO H OH

CH2OH D-(+)-glyceraldehyde * CH2CHCH O OH OH CHO HO H CH2OH L-(-)-glyceraldehyde D & L are used to relate configuration of the chiral center most removed from the reducing group ( C=O ). If the -OH is on the right in the Fischer projection, then it is D, if the -OH is on the left, then it is L 23.2: Fischer Projections and the D, L Notation. Representation of a three-dimensional molecule as a flat structure (Ch. 7.7). Tetrahedral carbon represented by two crossed lines:

horizontal line is coming out of the plane of the page (toward you) substituent (R)-(+)-glyceraldehyde (S)-(-)-glyceraldehyde vertical line is going back behind the plane of the paper (away from you) carbon 6 before the R/S convention, stereochemistry was related to (+)-glyceraldehyde 7 D-glyceraldehyde L-glyceraldehyde

R-(+)-glyceraldhyde S-(-)-glyceraldhyde (+)-rotation = dextrorotatory = d (-)-rotation = levorotatory = l D-carbohydrates have the -OH group of the highest numbered chiral carbon pointing to the right in the Fischer projection as in R-(+)-glyceraldhyde For carbohydrates, the convention is to arrange the Fischer projection with the carbonyl group at the top for aldoses and closest to the top for ketoses. The carbons are numbered from top to bottom. Carbohydrates are designated as D- or L- according to the stereochemistry of the highest numbered chiral carbon of the Fischer projection. If the hydroxyl group of the highest numbered chiral carbon is pointing to the right, the sugar is designated as D (Dextro: Latin for on the right side). If the hydroxyl group is pointing to the left, the sugar is designated as L (Levo: Latin for on the left side). Most naturally occurring carbohydrates are of the D-configuration.

8 23.3: The Aldotetroses. Glyceraldehyde is the simplest carbohydrate (C3, aldotriose, 2,3-dihydroxypropanal). The next carbohydrate are aldotetroses (C4, 2,3,4-trihydroxybutanal). 9 Manipulation of Fischer Projections 1. Fischer projections can be rotate by 180 (in the plane of the page) 10 only! 180 180 Valid Fischer projection

Valid Fischer projection a 90 rotation inverts the stereochemistry and is illegal! 11 90 This is not the correct convention for Fischer projections Should be projecting toward you Should be projecting away you This is the correct convention for Fischer projections and is the enantiomer 2. If one group of a Fischer projection is held steady, the other three groups can be rotated clockwise or counterclockwise. 120

hold steady hold steady 120 hold steady 120 hold steady 120 hold steady hold steady

12 Symmetry 13 Monarch butterfly: bilateral symmetry= mirror symmetry Whenever winds blow butterflies find a new place on the willow tree -Basho (~1644 - 1694) I anticipate organic chemistry class highlight of my day - Rizzo 13

aldotetroses * * CH2CHCHCH O OH OHOH CHO H OH H OH CH2OH CHO HO H HO H CH2OH D-erythrose

L-erythrose CHO H OH HO H CH2OH CHO HO H H OH CH2OH L-threose D-threose

(+)-glucose? An aldohexose Emil Fischer (1902) Four chiral centers, 24 = 16 stereoisomers * * * * CH2CHCHCHCHCH O OH OHOHOHOH CHO OH? CH2OH Epimers stereoisomers that differ only in configuration about one chiral center. H HO H H CHO

OH H OH OH CH2OH D-glucose HO HO H H CHO H H OH OH CH2OH D-mannose

epimers H OH H HO H H HO HO HO H H H OH OH

CHO OH H OH OH CH2OH H OH HO HO H H H OH OH H

OH H beta-(+)-glucose CH2OH O OH H H alpha-(+)-glucose H HO OH

CH2OH O OH OH H H OH H OH OH Addition of alcohols to aldehydes/ketones: R O

C H + R'OH OH R C H OR' hemiacetal geminal ether/alcohol reducing! OR' R C H OR' acetal geminal diether non-reducing!

H OH HO HO HO H H OH H OH H HO H H CHO

OH H OH OH CH2OH H OH HO HO HO H H H OH OH nucleophilic addition of -OH on carbon 5 to the aldehyde functional group

H OH H HO H H CHO OH H OH OH CH2OH H HO H HOH2C CH O OH H

OH H OH rotate C-5 OH to rear HO HO HO H H H OH OH H OH

HO HO HO H H OH H OH H OH H OH HO HO HO

H H alpha O 4H-Pyran H OH OH HO HO HO H H

hemiacetal OH H beta D-glucopyranoses OH H H H HOHO O HO H H OH

OH H HOHO O HO H H H OH H alpha furanose form beta furanose form D-glucofuranoses O furan OH

H OH H OH HO HO HO H H H OH OH HO HO

HO alpha H H OH H OH beta anomers - epimers at C-1 chair conformations - alpha has one group axial beta has all groups equatorial mutarotation in solution to 63.6% beta/36.4% alpha CH2OHO H

H OH CH2OH OH H OH alpha-D-fructofuranose CH2OH O HO H H OH H OH CH2OH D-fructose

CH2OHO H H OH OH OH H CH2OH beta-D-fructofuranose Disaccharides: (+)-maltose malt sugar two glucose units (alpha) (+)-cellobiose

two glucose units (beta) (+)-lactose milk sugar galactose & glucose (+)-sucrose table sugar glucose & fructose H OH HO HO HO H H

OH H H OH HO O HO HO HO HO H H H H

(+)-maltose H OH two glucose units alpha C-1 to C-4 OH H OH reducing sugar H OH O OH HO H HO H

H (+)-cellobiose OH H OH two glucose units beta C-1 to C-4 reducing sugar HO OH H OH HO H

HO H H O OH HO H galactose beta C-1 to C-4 glucose HO H H (+)-lactose OH H

OH reducing sugar HO HO HO H H OH acetal non-reducing H CH2OH H OH

OH O H OH CH2OH HO H (+)-sucrose glucose alpha C-1 to beta C1 fructose Polysaccharides starch cellulose Starch

20% amylose (water soluble) 80% amylopectin (water insoluble) amylose + H2O (+)-maltose (+)-maltose + H2O (+)-glucose starch is a poly glucose (alpha-glucoside to C4) O O O O O O O O O O

O O O O O O Amylopectin + H2O (+)-maltose (+)-maltose + H2O (+)-glucose Also a polyglucose, but branched every 20-25 units: O O O O O

O O O O O O O O O O O O O

O CH2 O O O O O O O O O Cellulose is a polyglucose with a beta-linkage: O O

O O O O O O O O O O O O O O The Complex Carbohydrates Fiber Sources Dietary fibers are found in plant foods. Functional fibers are health-benefiting fibers that are added to foods or supplements. Total fiber considers both dietary and functional fibers. Resistant starches escape digestion and are found in legumes, raw potatoes and unripe bananas. Phytic acid or phytate has a close association with

fiber and binds some minerals. 2008 Thomson - Wadsworth Carbohydrate Digestion In the mouth, the salivary enzyme amylase begins to hydrolyze starch into short polysaccharides and maltose. In the stomach, acid continues to hydrolyze starch while fiber delays gastric emptying and provides a feeling of fullness (satiety).

2008 Thomson - Wadsworth Digestion and Absorption of Carbohydrates Carbohydrate Digestion In the small intestine, pancreatic amylase among other enzymes (maltase, sucrase, and lactase) hydrolyzes starches to disaccharides and monosaccharides. In the large intestine, fibers remain and attract water, soften stools and ferment. 2008 Thomson - Wadsworth

Digestion and Absorption of Carbohydrates 2008 Thomson - Wadsworth Carbohydrate Absorption Primarily takes place in the small intestine Glucose and galactose are absorbed by active transport. Fructose is absorbed by facilitated diffusion.

2008 Thomson - Wadsworth Digestion and Absorption of Carbohydrates 2008 Thomson - Wadsworth Monosaccharides, the end products of carbohydrate digestion, enter the capillaries of the intestinal villi. In the liver, galactose and fructose are converted to glucose. Small intestine Monosaccharides travel

to the liver via the portal vein. Stepped Art Fig. 4-11, p. 110 Lactose Intolerance Symptoms include bloating, abdominal discomfort, and diarrhea. Causes include lactase deficiency due to a natural decrease that occurs with aging or damaged intestinal villi. Prevalence

Lowest in Scandinavians and northern Europeans Highest in Southeast Asians and native North Americans 2008 Thomson - Wadsworth Digestion and Absorption of Carbohydrates Lactose Intolerance - Dietary Changes Increase consumption of milk products gradually. Mix dairy with other foods. Spread dairy intake throughout the day.

Use of acidophilus milk, yogurt, and kefir (fermented products) Use of enzymes Individualization of diets Must be careful that vitamin and mineral deficiencies do not develop 2008 Thomson - Wadsworth Digestion and Absorption of Carbohydrates Glucose in the Body A Preview of Carbohydrate Metabolism The body stores glucose as glycogen in liver and muscle cells. The body uses glucose for energy if glycogen stores are available. If glycogen stores are depleted, the body makes

glucose from protein. Gluconeogenesis Protein-sparing is the conversion of protein to glucose. action is having adequate carbohydrate in the diet to prevent the breakdown of protein for energy. 2008 Thomson - Wadsworth Glucose in the Body A Preview of Carbohydrate Metabolism Making ketone bodies from fat fragments The

accumulation of ketone bodies in the blood is called ketosis. Ketosis The upsets the acid-base balance in the body. body can use glucose to make body fat when carbohydrates are consumed excessively. 2008 Thomson - Wadsworth Glucose in the Body The Constancy of Blood Glucose Maintaining Glucose Homeostasis

Low blood glucose may cause dizziness and weakness. High blood glucose may cause fatigue. Extreme fluctuations can be fatal. 2008 Thomson - Wadsworth Glucose in the Body The Constancy of Blood Glucose The Regulating Hormones

Insulin levels. moves glucose into the cells and helps to lower blood sugar Glucagon brings glucose out of storage and raises blood sugar levels. Epinephrine of stress. Balance acts quickly to bring glucose out of storage during times glucose within the normal range by eating balanced meals regularly with adequate complex carbohydrates.

Blood glucose can fall outside the normal range with hypoglycemia or diabetes. 2008 Thomson - Wadsworth 2008 Thomson - Wadsworth Glucose in the Body The Constancy of Blood Glucose Diabetes Type 1 diabetes is the less common type with no insulin produced by the body. Type 2 diabetes is the more common type where fat cells resist insulin.

Prediabetes is blood glucose that is higher than normal but below the diagnosis of diabetes. Hypoglycemia is low blood glucose and can often be controlled by dietary changes. 2008 Thomson - Wadsworth Glucose in the Body The Constancy of Blood Glucose Glycemic response is how quickly the blood glucose rises and elicits an insulin response.

Glycemic index classifies foods according to their potential for raising blood glucose. Glycemic load refers to a foods glycemic index and the amount of carbohydrate the food contains. The benefit of the glycemic index is controversial. 2008 Thomson - Wadsworth 2008 Thomson - Wadsworth Health Effects and Recommended Intakes of

Sugars Sugar poses no major health problem except dental caries. Excessive intakes may displace nutrients and contribute to obesity. Consuming foods with added sugars should be limited. Naturally occurring sugars from fruits, vegetables and milk are acceptable sources. 2008 Thomson - Wadsworth

Health Effects and Recommended Intakes of Sugars Health Effects of Sugars Foods with added sugars have sugars listed as a first ingredient. Nutrient deficiencies may develop from the intake of empty kcalories. Just because a substance is natural does not mean it is nutritious. (Example: honey) Dental caries may be caused by bacteria residing in dental plaque and the length of time sugars have

contact with the teeth. 2008 Thomson - Wadsworth 2008 Thomson - Wadsworth Enam el Caries Dentin Gu m Pulp (blood vessels, nerves) Crow n

Bon e Root canal Nerv e Blood vessel Stepped Art Fig. 4-14, p. 119 Health Effects and Recommended Intakes of Sugars Controversies Surrounding Sugars Excessive sugar intake can contribute to the

development of body fat. Sugar may be able to alter blood lipid levels and contribute to heart disease in some. There is no scientific evidence that sugar causes misbehavior in children and criminal behavior in adults. There is a theory that sugar increases serotonin levels, which can lead to cravings and addictions. 2008 Thomson - Wadsworth Health Effects and Recommended Intakes of Sugars Recommended Intakes of Sugars The USDA Food Guide states that added sugars can be included in the diet as part of discretionary kcalories.

Dietary Guidelines state to limit intake of foods and beverages that are high in added sugars. DRI suggest added sugars should contribute no more than 25% of a days total energy intake. 2008 Thomson - Wadsworth Health Effects and Recommended Intakes of Starch and Fibers Health Effects of Starch and Fibers May be some protection from heart disease and stroke

Soluble fibers bind with bile and thereby lower blood cholesterol levels. Fiber may also displace fat in the diet. Reduce the risk of type 2 diabetes by decreasing glucose absorption Enhance the health of the GI tract which can then block the absorption of unwanted particles May protect against colon cancer by removing potential cancer-causing agents from the body 2008 Thomson - Wadsworth

Health Effects and Recommended Intakes of Starch and Fibers Health Effects of Starch and Fibers Promote weight control because complex carbohydrates provide less fat and added sugar. Harmful effects of excessive fiber intake Displaces energy and nutrient-dense foods Abdominal discomfort and distention

May interfere with nutrient absorption 2008 Thomson - Wadsworth Health Effects and Recommended Intakes of Starch and Fibers Recommended Intakes of Starch and Fibers RDA for carbohydrate is 130 g per day, or 45-65% of energy intake. Daily Value is 300 grams per day. Dietary Guidelines encourage a variety of whole grains, vegetables, fruits and legumes daily. Healthy People 2010 recommends six servings of grains and five servings of fruits and vegetables. 2008 Thomson - Wadsworth

Health Effects and Recommended Intakes of Starch and Fibers Recommended Intakes of Fiber FDA recommends 25 grams for a 2,000-kcalorie diet. DRI at 14 g per 1000 kcalorie intake (28 grams for a 2,000 kcalorie diet) American Dietetic Association recommends 20-35 g per day.

World Health Organization suggests no more than 40 g per day. 2008 Thomson - Wadsworth 2008 Thomson - Wadsworth Health Effects and Recommended Intakes of Starch and Fibers From Guidelines to Groceries Grains encourage whole grains Vegetables starchy and nonstarchy vegetables differ in carbohydrate content Fruits vary in water, fiber and sugar content Milks and Milk Products contain carbohydrate;

cheese is low Meat and Meat Alternates meats are low but nuts and legumes have some carbohydrate Food labels list grams of carbohydrate, fiber and sugar; starch grams can be calculated. 2008 Thomson - Wadsworth 2008 Thomson - Wadsworth 2008 Thomson - Wadsworth Alternatives to Sugar Artificial Sweeteners Also called nonnutritive sweeteners Saccharin

Used primarily in soft drinks and as a tabletop sweetener Rapidly excreted in the urine Does not accumulate in the body Has been removed from list of cancer-causing substances 2008 Thomson - Wadsworth Artificial Sweeteners

Aspartame General purpose sweetener Warning about phenylalanine for those with PKU Controversial finding that aspartame may have caused cancer in rats Excessive intake should be avoided by those with epilepsy 2008 Thomson - Wadsworth

2008 Thomson - Wadsworth Asparti Phenylalani c acid ne Methyl group hydrolyz ed Methan ol Oxidize d Formaldehy de Oxidize d Stepped Art Carbon

Fig. H4-2, p. 134 Artificial Sweeteners Acesulfame-K (acesulfame potassium) Research confirms safety 2008 Thomson - Wadsworth Artificial Sweeteners Sucralose Made from sugar

Passes through digestive tract Neotame Most recent on the market Very sweet Phenylalanine not an issue 2008 Thomson - Wadsworth

Artificial Sweeteners Tagatose Used for foods and beverages Provides less kcalories than sugar High doses can cause flatulence and loose stools. Alitame and Cyclamate

Pending FDA approval Approved in other countries 2008 Thomson - Wadsworth Artificial Sweeteners Acceptable Daily Intake (ADI) is the level of consumption, maintained every day and still safe by a wide margin. Moderation and variety are still recommended. Artificial Sweeteners and Weight Control

Much Using research still being done artificial sweeteners will not automatically reduce energy intake. 2008 Thomson - Wadsworth Stevia An Herbal Alternative Lacks research Classified as a dietary supplement

Not required to have testing and FDA approval 2008 Thomson - Wadsworth Sugar Replacers Also called nutritive sweeteners, sugar alcohols, and polyols Maltitol, mannitol, sorbitol, xylitol, isomalt, and lactitol Absorbed more slowly and metabolized differently in the body Low glycemic response

Side effects include GI discomfort 2008 Thomson - Wadsworth What Is Diabetes? Learning Points Know the difference between Type 1 and Type 2 diabetes Know the job of glucose

Know the job of insulin List some health factors related to getting Type 2 diabetes Type 1 Diabetes Body does not make insulin Usually develops in children or young adults Normal Weight

Must take insulin daily to live Type 2 Diabetes Cells do not use insulin properly Not enough insulin being produced Generally develops in adulthood Becoming more common in children due to obesity Common in persons who are overweight

Many different ways to treat, including diet and exercise, pills, or insulin Type 2 Diabetes, Key Concepts Obesity Insulin Resistance Elevated Insulin Levels

Reduced ability to make insulin Insulin Resistance Common in persons who are overweight Insulin not as effective, and does not allow glucose into cells efficiently, causing blood sugar levels to rise There is enough insulin activity to prevent diabetic coma What Is Diabetes: How Insulin Works Insulin Insulin Receptor

How Insulin Works Insulin is a hormone made in your pancrease It works like a key to unlock cells so that blood sugar (glucose) can enter Glucose is then used by the body as fuel What Is Diabetes: How Insulin Works Insulin Fills Receptor Sites

insulin cell cell Receptor Site insulin glucose Insulin Passageways glucose glucose What Is Diabetes: Insulin Resistance Due to Excess Weight glucose

insulin insulin glucose cell glucose glucose What Is Diabetes: Normal Blood Glucose & Insulin Levels Normal Blood Glucose & Insulin Levels mg/dL 150 100

50 0 Early am Early pm Overnight Blood Glucose Level Plasma Insulin Level 2008 Thomson - Wadsworth Diabetes Pills: Oral Medications Diabetes Pills: Sulfonylureas These tell the pancreas to

make more insulin Diabetes Pills: Names of Sulfonyureas Brand Name Generic Name Diabeta Micronase Glynase glyburide Glucotrol Glucotrol XL glipizide Amaryl

glimepiride Diabetes Pills: Things to know about sulfonylureas Main thing to watch out for is having too many blood sugars. low If this happens, your doctor will give you a lower dose. Take the same way everyday

Glucotrol XL cannot be crushed or cut in half; might see its empty shell in toilet Diabetes Pills: Metformin Tells the liver to stop sending out sugar Diabetes Pills: Metformin Comes as generic metformin or brand name Glucophage Also comes in a long-acting form Diabetes Pills:

Things to know about metformin Can help people lose some weight Main side effects are upset stomach and diarrhea These usually get better after about 1 week Taking with food can help Does not cause blood sugar to go too low

Cannot be used in kidney disease or certain kinds of heart failure. Talk with doctor if you have these. Contact doctor if you notice new fatigue, nausea, muscle pain/weakness, or fast breathing because these could be signs of a serious side effect Diabetes Pills: Glitazones These help insulin in your body work better Diabetes Pills: Names of Glitazones Avandia and Actos

Only come as brand name pills Diabetes Pills: Things to know about glitazones The more common side effects of these are weight gain and swelling People with heart failure should discuss this with their doctor before taking Occasional blood work to test the liver is recommended, although liver problems on

this medicine are very rare These pills usually take 6 to 12 weeks before you can see their full benefit on blood sugar These are expensive Diabetes Pills: Meglitinides These tell the pancreas to make more insulin These are taken with meals, so you skip a dose if you

skip a meal Diabetes Pills: Names of Meglitinides Prandin and Starlix Only come as brand name pills Diabetes Pills: Meglitinides Things to know Main side effect to watch out for is low sugars

Might have a lower chance of having lows compared with sulfonylureas These are expensive

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