Bio1100 Chapter 13, Carbohydrates

Disaccharides

A disaccharide •consists of two monosaccharides linked together •is formed when two monosaccharides combine in a dehydration reaction. The most common disaccharides are maltose, lactose, and sucrose

Identify the monosaccharides in each of the following: A. Lactose (1) α-D-glucose (2) β-D-fructose (3) β-D-galactose B. Maltose (1) α-D-glucose (2) β-D-fructose (3) β-D-galactose C. Sucrose (1) α-D-glucose (2) β-D-fructose (3) β-D-galactose

A. Lactose (1) α-D-glucose (3) β-D-galactose B. Maltose (1) α-D-glucose C. Sucrose (1) α-D-glucose (2) β-D-fructose

Melibiose is a disaccharide that is 30 times sweeter than sucrose. A. What are the monosaccharide units in melibiose? B. What type of glycosidic bond links the monosaccharides? C. Identify the structure as α- or β-melibiose.

A. What are the monosaccharide units in melibiose? a-D-galactose and a-D-glucose B. What type of glycosidic bond links the monosaccharides? a-1,6-glycosidic bond C. Identify the structure as α- or β-melibiose. α-melibiose

Chemistry Link to Health: Blood Types

Blood types A, B, AB, and O are determined by terminal saccharides attached to the surface of red blood cells. Blood type •O has three common terminal monosaccharides: N-acetylglucosamine, galactose, and fucose •A contains the same three monosaccharides, but in addition, a molecule of N-acetylgalactosamine is attached to galactose in the saccharide chain •B also contains the same three monosaccharides, but in addition, a second molecule of galactose is attached to the saccharide chain •AB consists of the same monosaccharides found in blood types A and B •

Disaccharides

Lactose is a disaccharide found in milk and milk products. It contains the monosaccharides, galactose and glucose.

Carbon Cycle

Photosynthesis 6CO2 + 6H2O + energy -----> Respiration <---- C6H12O6 + 6O2

Chemistry Link to Health: Blood Types

The structures of monosaccharides N-acetylglucosamine, N-acetylgalactosamine, fucose, and galactose are as follows:

Maltose is •

a disaccharide also known as malt sugar •composed of two a -D-glucose molecules •obtained from the hydrolysis of starch •used in cereals, candies, and brewing •found in both the a and β forms. Maltose is linked by an a-1,4-glycosidic bond formed from the a —OH on carbon 1 of the first glucose and — OH on carbon 4 of the second glucose.

Lactose •is a

disaccharide found in milk and milk products •makes up 6-8% of human milk and about 4-5% of cow's milk. Lactose is a disaccharide of β-D-galactose and α- or β-D-glucose. The bond in lactose is a β-1,4-glycosidic bond because the —OH group on carbon 1 of β-D-galactose forms a glycosidic bond with the —OH group on carbon 4 of a D-glucose molecule.

Sucrose, or table sugar, •is obtained from

sugar cane and sugar beets •consists of α-D-glucose and β-D-fructose •has an α,β-1,2-glycosidic bond between carbon 1 of glucose and carbon 2 of fructose •cannot form an open chain and cannot be oxidized •cannot react with Benedict's reagent and is not a reducing sugar

Saccahrin

• •If temperatures rise above 300° C saccharin will boil. • Saccharin's relative low level of reactance makes this substance ideal for cooking because it remains stable at high temperatures. •Saccharin can also be dissolved easily into water, another good quality for food preparation. It is non-reactive in water at temperatures of as much as 150° C and at common pH levels measuring anywhere from 2 to 7. It's natural density is 0.828 g/mL. •The hydrogen bond is what reacts to cause the sensation of a sweet taste in the mouth. Upon digestion saccharin does not break down; it remains unchanged throughout digestion

Benedict's Test

•A test for monosaccharides includes the use of benedict's reagent (blue color) • •Once the reagent is added and heat is applied, the solution will change from blue to green, yellow or orange (depending on the concentration of sugar present) • •Cu 2+ reduced to Cu +

important carbohydrate affects

•Alpha amylase breaks down starches • •Pancreatic disease affects amylase levels

Plant Starch

•Composed of 2 kinds of polysaccharides: 1) Amylose (20% of starch) - composed of 250 - 4000 glucose units in an unbranched chain 2) Amylopectin (80% of starch) - branched chains of glucose units •Hydrolyze in water to form maltose and finally glucose

Carbohydrates

•Consist of carbon, hydrogen and oxygen •Also called saccharides •Simple carbohydrates are sugars -Have formulas of: Cn(H2O)n - C:H:O ratio of 1:2:1 •Complex carbohydrates are contained in many foods (bread, rice, pasta)

Glucose Isomers

•D Glucose can have two sterioisomers

Important Monosaccharides

•Galactose (C6H12O6) -doesn't occur free in nature -composes the dissacharide lactose -found in cellular membranes of brain and nervous system - •Fructose (C6H12O6) -fruit sugar -composes the dissacharide sucrose (table sugar) -sweetest of the carbohydrates -converted into glucose in the bloodstream

Important Monosaccharides

•Glucose (C6H12O6) - also known as dextrose -found in fruits, veggies, corn syrup and honey -building block for many di- and polysaccharides -can be converted to glycogen and stored in liver and muscles -normally at concentration of 70 - 100 mg / 100 ml of blood

Animal Starch: Glycogen

•Highly branched chain of glucose •Stored in liver and muscles of animals •Hydrolyzed in cells to provide glucose for energy between meals

Hydrolysis of Carbohydrates

•In the presence of water, disaccharides and polysaccharides completely hydrolyze to form monosaccharides:

Fermentation

•In the presence of yeast, glucose & fructose will produce ethanol & carbon dioxide • (glucose or fructose)C6H12O6 -->> Yeast--->>>2C2H5OH + CO2 (ethanol) • • • •The disaccharides maltose & sucrose will also undergo fermentation •Polysaccharides and lactose will not ferment

Iodine Test

•Iodine (I2) is used to test for the presence of starch • •A dark blue, black or brown color develops in the presence of starch • •Iodine will remain a yellow color in the presence of mono- and disaccharides

Common Dissacharides

•Maltose (malt sugar) -found in grains & barley -obtained from the hydrolysis of starch - •Lactose (milk sugar) -found in milk & milk products -lactose-intolerance is due to the lack of sufficient enzyme to break down lactose - •Sucrose (table sugar) -extracted from sugar cane and sugar beets

Types of Carbohydrates

•Monosaccharides -simplest carbohydrates -consist of one sugar • •Disaccharides -consist of two monosaccharides joined - •Polysaccharides -complex carbohydrates -may contain thousands of monosaccharides

Cyclic Monosaccharides

•Most 5 & 6 carbon sugars form ring structures

Carbon Cycle

•Photosynthesis: -process performed by plants that produces carbohydrates (usually glucose) and O2 -requires sunlight energy, CO2 and water • •Respiration: -occurs in the cells of living organisms -glucose is oxidized to release energy and forms carbon dioxide and water

Polysaccharides

•Polymer of many monosaccharides joined together • •Starch, glycogen and cellulose are all polymers of glucose

Cellulose

•Structural polysaccharide that composes wood and plants •Long unbranched chains of glucose •Very resistant to hydrolysis •Humans lack the enzyme to hydrolyze cellulose •Termites have the enzyme

Sacchrin

•The chemical formula for saccharin is C7H5NO3S. The molar mass for saccharin is 183.19 grams per mole. Saccharin consists mostly of carbon; carbon makes up 45.89% of the composition of saccharin by mass. •The mass of saccharin is also 2.75% hydrogen, 7.65% nitrogen, 26.20% oxygen, and 17.50% sulfur. By number saccharin is 41% carbon, 29% hydrogen, 6% nitrogen, 18% oxygen, and 6% sulfur. Saccharin melts at 228.8° to 229.7° C. •Structurally, saccharin is made up of two connected rings; the first ring is a phenyl ring and the second is a 5 membered ring with a nitrogen, a carboxyl group, and a sulfone group beside the nitrogen. Due to the presence of a nitrogen, the molecule is heterocyclic.

Monosaccharides

•Triose - 3 carbon sugar •Tetrose - 4 carbon sugar •Ribose - 5 carbon sugar •Hexose - 6 carbon sugar • •Many sugars are isomers of each other -same molecular formula -different structural formulas

Monosaccharides

•Unbranched chains of 3 - 8 carbons •One carbon is in a carbonyl group: • •Other carbons are attached hydroxyl groups (— OH)

Aspartame is

•marketed as NutraSweet and Equal •a noncarbohydrate sweetener made of aspartate and a methyl ester of the amino acid phenylalanine

Sucralose is

•marketed as Splenda •made from sucrose by replacing some of the hydroxyl groups with chlorine atoms