Carbohydrates

Discussion Questions:(Groups of 2 – 5 minutes!!!) List some food items rich in carbohydrates. What is the difference between complex

carbohydrates versus simple carbohydrates? Would you recommend a person who wants

to lose weight to adopt a low-carb diet?

Canada’s Food Guide

Carbohydrates make up the largest volume of our daily food

Carbohydrates are found in: grain flour, cereals, pasta, potatoes and other vegetables, fruits, syrups, honey, candy, pop, juice, milk as well as in the pure crystalline form of our familiar table "sugar".

Functions of Carbohydrates

Energy source Plays a vital part in the digestion,

metabolism, and oxidation of protein and fat.

Too much carbohydrate = Glycogen in liver OR Fat

Simple versus Complex Carbohydrates Simple Carbs:

Quick source of energy (do not supply other nutrients or fiber) Quickly absorbed – rapid increase in blood sugar level followed by quick decline Small molecules (glucose, fructose, maltose, sucrose, lactose) Found in: fruit, fruit juice, table sugar, honey, soft drinks, and other sweets

Complex Carbs: Supply energy and other nutrients and fiber Slowly digested – steady slow rise in blood sugar level Large molecules (starch and dietary fiber) Starch: breaks down into smaller carbs; supplies long, sustained energy to the

body bread, cereal, potatoes, pasta, rice, and legumes (dried peas and beans)

Dietary fiber: found in plant cells (non-digestible part of plants) tough and stringy it does not break down completely in the body Essential for regulating the body (digestion). bran, whole-grain foods, raw vegetables and fruit (especially the seeds and skins),

legumes, nuts, seeds and popcorn

Some General Chemical Info

Hydrophilic organic molecule General formula

(CH2O)n , n = number of carbon atoms

for glucose, n = 6, so formula is C6H12O6

Names of carbohydrates word root sacchar- or the suffix -ose often used

monosaccharide or glucose

Aldoses and Ketoses Aldoses contain the aldehyde group Ketoses contain the ketone group

Ring Formation

In aqueous solution, the aldehyde and ketone groups react with hydroxyl (-OH) group belonging to the same molecule

Monosaccharides

Simplest carbohydrates

General formula is C6H12O6

structural isomers Three major monosaccharides

glucose, galactose and fructose mainly produced by digestion of

complex carbohydrates

Sugar Derivatives The hydroxyl groups of a simple

monosaccharide can be replaced by other groups

Alpha () and Beta () Links

The hydroxyl group on the carbon that carries the aldehyde or ketone can rapidly change from one position to the other

Disaccharides

Pairs of monosaccharides

Three major disaccharides sucrose

glucose + fructose lactose

glucose + galactose maltose

glucose + glucose

Dehydration Synthesis of a Disaccharide

Dehydration synthesis of two glucose molecules results in the formation of maltose

The C-O-C bond formed is called a glycosidic bond

Polysaccharides Starch, cellulose and glycogen

long chains of glucose form these polysaccharides Starch produced by plants is digested by amylase Cellulose gives structure to plants, fiber to our diet

Starch Hydrolysis

The digestion of starch occurs by the hydrolysis of the glycosidic bond.

Amylase is the enzyme. Maltose is the product.

Polysaccharides

Glycogen is an energy storage polysaccharide produced by animals

Liver cells synthesize glycogen after a meal to maintain blood glucose levels

Carbohydrate Functions Source of energy Conjugated carbohydrates

glycolipids external surface of cell membrane

glycoproteins external surface of cell membrane mucus of respiratory and digestive tracts

proteoglycans carbohydrate component dominant cell adhesion, gelatinous filler of tissues (eye) and lubricates

joints

Moieties of Macromolecules

A moiety is a chemically different component of a conjugated macromolecule Glycolipid glycoprotein