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Carbohydrates
• carbohydrates, also known as sugars, are found in all living organisms.
• They are essential to the very source of life (ex. Ribose sugars in DNA and RNA) or sustaining life itself (ex. Metabolic conversion of carbohydrates into usable biochemical energy, ATP).
• Another important role of carbohydrates is structural (ex. Cellulose in plants).
Carbohydrates names
• General names for carbohydrates include sugars, starches, saccharides, and polysaccharides.
• The term saccharide is derived from the Latin word "sacchararum" from the sweet taste of sugars.
• The name "carbohydrate" means a "hydrate of carbon."
• General formula of carbohydrates
Where do Carbohydrates originate?
• As glucose in plants!
• Glucose
• Most abundant carbohydrate
• Produced by plants (& other photosynthetic organisms) via photosynthesis
• Simple or complex
•This is the general equation for photosynthesis—the
process of capturing sunlight energy and converting it to
chemical energy.
•C6H12O6 and O2. = products
•CO2 and H2O. = reactants
General properties of carbohydrates
• Many carbohydrates are soluble in water.
• The usual chemical test for the simpler carbohydrates is
heating with Benedict's solution.
• The formula for a carbohydrate is (CH2O)n or Cn(H2O)n
• The n represents the number of atoms for each element.
• A primary energy source, especially for neurons (nerve cells)
• found in Grains, fruits and vegetables
Carbohydrates • Carbohydrates Contain the Elements:
Carbon
Hydrogen
Oxygen
• They Are divided Into four Groups Known As:
Monosaccharides
Disaccharides
Oligosaccharides
Polysaccharides
Classification of carbohydrates
Carbohydrates can be classified according to size into:
• Monosaccharides
• Disaccharides
• Oligosaccharides
• Polysaccharides (or glycans)
Monosaccharides
• Monosaccharides contain one sugar
unit such as glucose, galactose, fructose,
etc.
11
Monosaccharides consist of 1
sugar unit and this sugar unit may
contain: • Three Carbons = Triose
• Four Carbons = Tetrose
• Five Carbons = Pentose
• Six Carbons = Hexose
Glucose
The chemical formula
for glucose is C6H12O6.
It is a six sided ring.
Different forms of glucose structure
Importance of glucose
• Glucose serves as the primary energy source for the brain
and is also a source of energy for cells throughout the body.
• This energy helps the cells carry out the following
processes:
• nerve cell conduction.
• muscle cell contraction.
• active transport and the production of chemical
substances..
Other Monosaccharides
Disaccharides
• contain two sugar units. In almost all cases one
of the sugars is glucose, with the other sugar
being galactose, fructose, or another glucose.
Common disaccharides are maltose, lactose,
and sucrose.
In order to have a disaccharides
we should have Glycosidic Bond
• This is when two monosaccharides join to form a Disaccharide.
• The water is removed in this reaction in order to form this type of bond..
Glycosidic Bond
Above is the structures of a
Glycosidic bond.
It forms a Disaccharide
How to break the Glycosidic bond?
By hydrolysis (( dissolving it in water)) of the
disaccharides (( opposite to the way of its formation)).
Instead of water been taken away water is added.
By this reaction the disaccharides are simplified again into
two monosaccharides
Disaccharides • Lactose: Milk sugar (glucose + galactose)
• Maltose: Malt sugar (glucose + glucose); by-product of digestion & fermentation in our bodies; substrate for fermentation in beer and liquor)
• Sucrose: Naturally occurring fruit sugar
Oligosaccharides
• They are formed of 3 to 10 sugar units
• A large number of oligosaccharides have been prepared
by partially breaking down more complex carbohydrates
(polysaccharides).
• Most of the few naturally occurring oligosaccharides are
found in plants.
• Raffinose, a trisaccharide found in many plants, consists
of melibiose (galactose and glucose) and fructose.
• Another plant trisaccharide is gentianose. Maltotriose, a
trisaccharide of glucose, occurs in some plants and in the
blood of certain arthropods.
Polysaccharides
• contain many sugar units in long polymer chains of many
repeating units. The most common sugar unit is glucose.
Common poly saccharides are starch, glycogen,
and cellulose..
Polysaccharides examples
• Starch: Storage form of glucose in plants
• Glycogen: Storage form of glucose in animals
• Fiber: Form of structural support elements of plants
Table of common carbohydrates
Name Derivation of name and Source Monosaccharides
Glucose From Greek word for sweet wine; grape sugar, blood
sugar, dextrose.
Galactose Greek word for milk--"galact", found as a component of
lactose in milk.
Fructose Latin word for fruit--"fructus", also known as
levulose,found in fruits and honey; sweetest sugar.
Ribose Ribose and Deoxyribose are found in the backbone
structure of RNA and DNA, respectively.
Table of common carbohydrates
Name Derivation of name and Source Disaccharides - contain two monosaccharides
Sucrose French word for sugar--"sucre", a disaccharide
containing glucose and fructose; table sugar, cane
sugar, beet sugar.
Lactose Latin word for milk--"lact"; a disaccharide found
in milk containing glucose and galactose.
Maltose French word for "malt"; a disaccharide containing
two units of glucose; found in germinating grains,
used to make beer.
Table of common carbohydrates
Name Derivation of name and Source Common Polysaccharides
Starch Plants store glucose as the polysaccharide starch. The cereal
grains (wheat, rice, corn, oats, barley) as well as tubers such
as potatoes are rich in starch.
Cellulose The major component in the rigid cell walls in plants is
cellulose and is a linear polysaccharide polymer with many
glucose monosaccharide units.
Glycogen This is the storage form of glucose in animals and humans
which is analogous to the starch in plants. Glycogen is
synthesized and stored mainly in the liver and the muscles.
Illustrating video
How to test the presence of
carbohydrates
(( By using Benedict reagent))
Will be
discussed in
the lectures
of lab 2
1-Digestion of Carbohydrates
2- Regulation of Blood Glucose
• Begins in the mouth
• Saliva hydrolyzes starch to short polysaccharides &
maltose
• Mechanical digestion with teeth
• Stops in stomach
• Resumes in Small Intestine
• Pancreatic amylase also digests carbohydrates to maltose
Digestion of Carbohydrates
Transport & Use
• ALL monosaccharides are converted to glucose by the liver
• Glucose circulating in the blood is our primary energy source
• Excess glucose is converted to glycogen by the liver
Storage of Glycogen
Regulation of Blood Glucose
1. Amount of glucose (and therefore, access to quick energy) in the blood
2. Pancreatic cells secrete two hormones, insulin and glucagon, which control level of glucose in the blood
Regulation of Blood Glucose:
Insulin
• After eating, pancreas releases:
• Insulin
• Stimulates cells of the body to absorb glucose from the bloodstream
• Stimulates the liver to absorb glucose and convert it to glycogen
Regulation of Blood Glucose: Insulin
Regulation of Blood Glucose:
Glucagon
• Glucagon
• Stimulates the breakdown (hydrolysis) of glycogen
to glucose to make quick energy available to cells
of the body
Regulation of Blood Glucose:
Glucagon
Illustrating video
