• Carbohydrate – (hydrated carbon)

• Carbohydrates have empirical formula Cx(H2O)y.

• Most abundant carbohydrate is glucose, C6H12O6.

• Two types of Carbohydrates – monosaccharides (simple sugars and polysaccharides.

CarbohydratesCarbohydrates

Monosaccharides – 1st type

Simplest form of carbohydratesClassified according to number of carbons

Triose – 3C’sPentose – 5C’sHexose – 6C’s

All have 2 or more alcohols and a carbonyl group

General Formula – CH2O

These simple sugars that cannot be broken down by hydrolysis with aqueous acids.

Examples - Glucose and Fructose are the main substrate for respiration, releasing energy for all cell processes.

Aldose sugar Ketose sugar

2 Common Mono-saccharides – both isomers C6H12O6

Each containmany OH groupswhich make thesemolecules solublein water.

This are the straightchain form ofthese sugars.

Monosaccharides

When these sugars are put in an (aq) solution, they undergo and internal reaction which results inthe more familiar ring structure

• Most glucose molecules are in the ring form.• Note the six-membered rings are not planar.• Focus on carbon atoms 1 and 5: if the OH groups are on

opposite sides of the ring, then we have -glucose; if they are on the same side of the ring, then we have -glucose.

• The - and - forms of glucose form very different compounds.

The ring form of sugars make it possible for another typeof isomer.

This OH is below the plane of the ring

This OH is above the plane of the ring

Disaccharides• Disaccharides are sugars formed by the condensation of

two monosaccharides. • Examples: sucrose (table sugar) and lactose (milk

sugar).• Glycoside linkage – “ether” bond formed when

monosaccharides combine to form disaccharides or polysaccharides (C-O-C).

• Disaccharides can be converted into monosaccharides by treatment with acid in aqueous solution.

Disaccharides

Lactose – glucose + galactose – found in milk

Maltose – glucose + glucose – product from starch digestion

Sucrose – glucose + fructose – table sugar

All have same molecular formula – C12H12O11

glycosidic linkage (known as 1,4 b/c of C’s involved

Polysaccharides• Polysaccharides are formed by condensation of several

monosaccharide units. • All polysaccharides are insoluble so they are ideal for

storage.• 3 common glucose based polysacch. = starch, glycogen,

and cellulose

• Main storage carbohydrate in plants – this is why food from plants are rich sources of starch – Ex. potatoes, rice, flour…

• Starch is a polymer of -glucose.• Made from two polysaccharides – amylose (straight

chain) and amylopectin (branched) • Starch contains 1,4 and 1,6 linkages.

1. Starch

Starch

Amylose – 1,4 linkage of -glucose monomers

Amylopectin – 1,4 and 1,6 linkageof -glucose monomers

• Also a polymer of -glucose.

• Sometimes called “animal starch” as it is the main storage carb in animals – found in the liver and muscles

• Contains many 1,6 branches

2. Glycogen

3. Cellulose• Cellulose is a structural material in plant cell walls.• Cellulose is a polymer of -glucose. It is linear.• Every other monomer is upside down – enables to

hydroxyl groups to form hydrogen bonds –gives support• The 1,4 linkage can be hydrolyzed by cellulase which is

absent in most animals, including mammals. (humans have some from bacteria in our gut, but not much)

Major Functions of Carbohydrates

1. Energy sources – (glucose)

2. Energy reserves (glycogen)

3. Structure (cellulose)Dietary Fiber – mainly plant material (lots of veggies and salad)

that is not hydrolyzed by enzymes secreted in the human digestive tract. (may be digested by microflora in the gut) Most is excreted intact by the body. Ex. Cellulose, hemicellulose, lignin and pectin

Starch and glycogen are easily broken down and absorbed in the body.

Importance –as fiber passes through the digestive system it helps stimulate the lining to produce mucus which helps smooth passage of undigested foods. May help prevent diverticulitis, IBS, colorectal cancer, constipation, obesity, Crohn’s disease, hemorrhoids, and diabetes mellitus.