CARBOHYDRATES – PROPERTIES AND FUNCTIONS.ppt

Carbohydrates are essentially substances that are made up of carbon, hydrogen and oxygen only.
The carbohydrates are divided into three broad categories, namely, monosaccharides, oligosaccharides and polysaccharides.
Carbohydrates function as lubricants in skeletal joints and help the cells to stick with each other and remain in place.

1. Mrs. R.Subha, M.Sc., M.Phil., D.C.T.,
Assistant Professor of Home Science

2. Carbohydrates are essentially substances that are made
up of carbon, hydrogen and oxygen only.
The carbohydrates are divided into three broad
categories, namely, monosaccharides, oligosaccharides
and polysaccharides.
Monosaccharidesrepresent the group of carbohydrates
that cannot be further hydrolyzed to smaller molecules.
They form the building blocks of the more complex
carbohydrates.
Oligosaccharidescomprise the low molecular weight
polymers that include the disaccharides and
trisaccharidesand compounds with as many as ten
monosaccharideslinked into single molecules.

3. Polysaccharidesare the carbohydrates which contain more than 10
monosaccharide units. They can be hydrolyzed into hundred or even thousands
of monosaccharide units.
The suffix –osein sugar is changed to –ansto describe the corresponding
polysaccharide.
Examples:
(1)Pentosans
(a) Arabans
(b) Xylans
(2)Hexosans
(a) Glucansàstarch, dextrin, glycogen, cellulose, inulin
(b)Mannans
(c)Galactans
(3)Complex polysaccharides
(a)Pectinsor pecticsubstances
(b)Gums
(c)Mucilages
(d)Algal polysaccharidesàAlginicacid and carrageenan.
(e)Bacterial polysaccharidesàXanthangum.

5. defined as polyhydroxyaldehydesor ketonesand
their derivatives.
Their general formula can be represented as
C
x(H
2O)
y.
Carbohydrates are formed in plant cells from
carbon dioxide and water in a process called as
photosynthesis.
1 g of carbohydrates provide 4 kcal energy.
In human food, the sources of carbohydrates are
cereals, roots, tubers, sugarcane and sugarbeet.
Carbohydrates are named according to sources
from which they are obtained e.g., fructose (fruit
sugar), lactose (milk sugar), xylose(wood sugar)
and cellulose (from cell membrane).

6. Most of the monosaccharides, disaccharides
and lower polysaccharides are sweet in taste,
whereas starch and cellulose are tasteless.
They exhibit stereoisomerism. Stereoisomers
are compounds whose structural formula is
same but arrangement of atoms in 3-
Dimensional space is different. E.g., with
respect to Carbon no. 5, Glucose has two
forms, D-glucose and L-glucose.

7. Theyexhibitopticalactivity.(Optical
activityisaphenomenoninwhicha
moleculerotatesplaneofplain
polarisedlight.Ifthemolecule
rotatestheplanetowardsleft,itis
designatedlevorotatory(-sign)and
iftheplaneisrotatedtowardsright,
themoleculeisdesignateddextro
rotatory(+sign).D-glucoserotates
planeofplainpolarisedlighttowards
rightwhileL-fructoserotatesit
towardsleft.

8. Thesugarsinwhichfreealdehydeorketone
groupsarepresentcanreduceFehling’s
solutionandBenedict’ssolutionarecalled
reducingsugars.Thesugarsinwhichfree
aldehydeorketonegroupsareabsentare
calledasnon-reducingsugars.Glucose,
fructose,lactoseetc.,arereducingsugars
whereassucroseisanon-reducingsugar.

9. They are a major part of total caloric intake.
Starch and glycogen serve as temporary
stores of glucose.
Water insoluble carbohydrates are major
components of cell wall in plant cells and cell
membrane in animal cells.
Carbohydrates function as lubricants in
skeletal joints and help the cells to stick with
each other and remain in place.

10. Satyanarayana U. & Chakrapani U. (2011),
“Biochemistry”. Books and Allied (P) Ltd. pp.
N. Shakuntala Manay & M. Shadaksharaswamy
(2001), “Foods: Facts and Principles”. New Age
International Publishers.