Carbohydrates
Discussion Questions:
(Groups of 2 – 5 minutes!!!)
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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
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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 =
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Glycogen in liver OR
Fat
Simple versus Complex Carbohydrates
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Simple Carbs:
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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:
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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
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bread, cereal, potatoes, pasta, rice, and legumes (dried peas and beans)
Dietary fiber:
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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
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Hydrophilic organic molecule
General formula
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(CH2O)n , n = number of carbon atoms
for glucose, n = 6, so formula is C6H12O6
Names of carbohydrates
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word root sacchar- or the suffix -ose often used
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monosaccharide or glucose
Aldoses and Ketoses
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Aldoses contain the aldehyde group
Ketoses contain the ketone group
Ring Formation
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In aqueous solution, the aldehyde and
ketone groups react with hydroxyl (-OH)
group belonging to the same molecule
Monosaccharides
• Simplest carbohydrates
• Mono = one, Saccharide =
sugar
• Glucose, Galactose, and
Fructose are examples of
monosaccharides
• They are all isomers of each
other because they have the
same molecular formula
(C6H12O6) but different
structures
Sugar Derivatives
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The hydroxyl groups of a simple
monosaccharide can be replaced by other
groups
Alpha (a) and Beta (b) Links
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The hydroxyl group on the carbon that carries
the aldehyde or ketone can rapidly change
from one position to the other
b
a
Disaccharides
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Pairs of
monosaccharides
Three major
disaccharides
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sucrose
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lactose
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glucose + fructose
glucose + galactose
maltose
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glucose + glucose
Dehydration Synthesis
of a Disaccharide
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Dehydration synthesis of two glucose molecules
results in the formation of maltose
The C-O-C bond formed is called a glycosidic
bond
Polysaccharides
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Starch, cellulose and glycogen
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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
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The digestion of starch occurs by the hydrolysis
of the glycosidic bond.
Amylase is the enzyme.
Maltose is the product.
Polysaccharides
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Glycogen is an energy storage
polysaccharide produced by animals
Liver cells synthesize glycogen after a meal
to maintain blood glucose levels
Carbohydrate Functions
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Source of energy
Conjugated carbohydrates
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glycolipids
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external surface of cell membrane
glycoproteins
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external surface of cell membrane
mucus of respiratory and digestive tracts
Moieties of Macromolecules
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A moiety is a chemically different component of a
conjugated macromolecule
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Glycolipid
glycoprotein