Carbohydrates are the sugars, starches and fibers found in fruits, grains, vegetables and milk products. Though often maligned in trendy diets, carbohydrates โ one of the basic food groups โ are important to a healthy diet.
2. Introduction
Carbohydrates (or saccharides) consist of only carbon, hydrogen
and oxygen
Carbohydrates come primarily from plants, however animals can
also biosynthesize them
Energy from the sun is stored in plants, which use photosynthesis
to convert carbon dioxide and water to glucose and oxygen
In the reverse process, energy is produced when animals oxidize
glucose during respiration
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3. Definition
Carbohydrates โ poly hydroxy aldehydes or poly
hydroxy-ketones of formula (CH2O)n, or
compounds that can be hydrolyzed to them.
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8. Types of carbohydrates
Monosaccharidesโcarbohydrates that cannot be
hydrolyzed to simpler carbohydrates; eg. Glucose or
fructose.
Disaccharidesโcarbohydrates that can be hydrolyzed
into two monosaccharide units; eg. Sucrose, which is
hydrolyzed into glucose andfructose.
Oligosaccharidesโcarbohydrates that can be
hydrolyzed into a few monosaccharideunits.
Polysaccharides โ carbohydrates that are polymeric
sugars; eg Starch orcellulose.
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12. Classification of Monosaccharides
Monosaccharides have 3-8 carbons in a chain, with one carbon in
a carbonyl group, and the other carbons attached to c groups
- An aldose has the carbonyl C1 (an aldehyde)
- A ketose has the carbonyl on C2 (a ketone)
-The number of carbons is indicated as follows: triose (3 Cโs),
tetrose (4 Cโs), pentose (5 Cโs), hexose(6 Cโs)
CH2OH
O
H OH
H OH
H OH
H OH
CH2OH
O
HO H
H OH
H OHH OH
H O
H O
CH2OH
Glyceraldehyde
(aldotriose)
CH2OH
Erythrulose
(ketotetrose)
CH2OH
Ribose
(aldopentose)
CH2OH
Fructose
(ketohexose)
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23. Aldoses and ketoses
Ketoses (e.g., fructose)
have a keto group, usually
at C2.
Aldoses (e.g., glucose)have
an aldehyde group at one
end.
H O
C
H C OH
HO C H
H C OH
H C OH
CH2OH
D-glucose
CH2OH
C O
HO C H
H C OH
H C OH
CH2OH
D-fructose
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25. Three Important Monosaccharides
D-Glucose is the most common monosaccharide
- Primary fuel for our cells, required for many tissues
- Main sources are fruits, vegetables, corn syrup and honey
- Blood glucose is maintained within a fairly small range
- Some glucose is stored as glycogen, excess is stored as fat
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26. D-Galactose comes from hydrolysis of the disaccharide
lactose
- Used in cell membranes of central nervous system
-Converted by an enzyme into glucose for respiration(lack
of this enzyme causes galactosemia, which can cause
retardation in infants if not treated by complete removal
from diet)
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27. D-Fructose is the sweetest carbohydrate
- Converted by an enzyme into glucose for respiration
- Main sources are fruits and honey
- Also obtained from hydrolysis of the disaccharide sucrose
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33. Amino Sugars
Amino sugars contain an -NH2 group in place of an -
OH group
๏ก only three amino sugars are common in nature:D-glucosamine,
D-mannosamine, and D-galactosamine
CHO
H NH2
HO H
H OH
H OH
CHO
H NHCCH3
HO H
H OH
H OH
CHO OCHO
H NH2
HO H
HO4 H
H OH
H2 N 2 H
HO H
H OH
H OH
CH2OH
D-Mannosamine
(C-2 stereoisomer
of D-glucosamine
CH2OH
D-Glucosamine
CH2OH
D-Galactosamine
(C-4 stereoisomer
of D-glucosamine)
CH2OH
N-Acetyl-D-
glucosamine
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36. Reducing sugar โ a carbohydrate that is oxidizedby Tollenโs,
Fehlingโs or Benedictโs solution.
Tollenโs: Ag+ ๏ Ag (silver mirror)
Fehlingโs or Benedictโs: Cu2+ (blue) ๏ Cu1+ (red
ppt)
These are reactions of aldehydes and alpha-hydroxyketones.
All monosaccharides (both aldoses and ketoses) and most*
disaccharides are reducing sugars.
*Sucrose (table sugar), a disaccharide, is not a reducing sugar.
Identification tests
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45. Diabetes mellitus (DM),
Diabetes mellitus (DM), commonly known as diabetes, is a group of metabolic
disorders characterized by a high blood sugar level over a prolonged period of
time.Symptoms often include frequent urination, increased thirst, and increased
appetite.
If left untreated, diabetescan cause Many complications.Acutecomplications can
includediabetic ketoacidosis, hyperosmolar hyperglycemic state, or death.
Serious long-term complications include cardiovascular disease, stroke, chronic
kidney disease, foot ulcers, damage to the nerves, damage to the eyes and cognitive
impairment.
Diabetes is due to either the pancreas not producing enough insulin, or the cells of
the body not respondingproperlyto the insulin produced.There are three main types
of diabetesmellitus.
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46. Lactose intolerance
Lactose intolerance is a decreased ability to digest lactose, a sugar
found in dairyproducts.
Those affected vary in the amount of lactose they can tolerate before
symptoms develop.
Symptoms may include abdominal pain, bloating, diarrhea, gas,
and nausea.These symptoms typically start thirty minutes to two hours
after eating or drinking milk-based food. Their severity typically
depends on the amount a person eats or drinks.
Lactose intolerance does not cause damage to the gastrointestinal tract.
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47. Galactosemia
Galactosemia (British galactosaemia, from
Greek ฮณฮฑฮปฮฑฮบฯฯฮถฮท + ฮฑฮฏฮผฮฑ, meaning galactose + blood, accumulation
of galactose in blood) is a rare genetic metabolic disorder that affects
an individual's ability to metabolize the sugar galactose properly.
Galactosemia follows an autosomal recessive mode of inheritance that
confers a deficiency in an enzyme responsible for adequate galactose
degradation.
Its incidence is about 1 per 60,000 births for people of European
ancestry. In other populations the incidence rate differs. Galactosaemia
is about one hundred times more common (1:480 births) in the Irish
Traveller population.
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48. Glycogen storage disease (GSD
A glycogen storage disease (GSD,
also glycogenosis and dextrinosis) is a metabolic disorder caused
by enzyme deficiencies affecting either glycogen synthesis, glycogen
breakdown or glycolysis (glucose breakdown), typically
in muscles and/or liver cells.
GSD has two classes of cause: genetic and acquired. Genetic GSD is
caused by any inborn error of metabolism (genetically
defective enzymes) involved in these processes. In livestock,
acquired GSD is caused by intoxication with
the alkaloid castanospermine.
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