Carbohydrates

What are Carbohydrates? Put simply…hydrocarbons. Empirical Formula CnH2nOn

Divided into three groups Monosaccharides Disaccharides Polysaccharides

Monosaccharides Monomers…single sugar molecules.

Let’s build glucose and fructose.

How are the molecules different? What functional groups are present?

Monomers in Use Ribose and 2-deoxyribose are pentoses

Used in DNA and RNA

Glucose, Galactose, and Fructose are hexoses Used in plants and animals for energy Build into larger biological molecules like

insulin.

Disaccharides Two monosaccharides joined by a

glycosidic bond. (ether) A water molecule is generated in the

process of bond formation. (condensation polymerization)

Disaccharides in Use Sucrose

Table Sugar Let’s build it! Join the glucose and fructose from earlier.

Lactose Milk sugar: glucose and galactose Lactose intolerant people lack the enzyme needed to

break lactose’s glycosidic bond.

Invert Sugar Bees use enzymes to break sucrose’s glycosidic bond to

create invert sugar, which is the sweet flavor in honey.

Polysaccharides Strings of more than 20

monosaccharides. Starch

Major source of food calories consumed by people Amylose (in rice!)= linear polysaccharide Amylopectin = branched polysaccharide Glycogen = highly branched, stored in muscles

and liver until converted to fat for long term storage.

Alpha and Beta Linkages Starch and Cellulose are

made of glucose. 2 isomer forms for

linkages- alpha and beta. Starch has alpha

linkages. (cis) Cellulose has beta

linkages. (trans)

Food uses of Carbohydrates Reducing sugars react with amino acids

in the Maillard Reaction (causes browning)

Polysaccharides bind water to thicken liquids into gels.

Used to stabilize suspensions, emulsions.

Pectin Pectin is a polysaccharide

made of galacturonic acid (galactose) molecules with beta linkages.

Found in green apples, lime peel, lemon peel

When heated with sugar at low pH, branched polymerization occurs to create a thick gels.