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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