2. CARBOHYDRATES
• Carbohydrate means "watered carbon" or carbon with
attached water molecules
• Carbohydrates
• are a group of Organic compounds containing Carbon,
hydrogen and oxygen with a ratio of two hydrogens for
every oxygen atom.
• They are also Called Saccharides
• They are most abundant molecules in nature
• Defined as
• Polyhydroxy aldehyde or ketones or Compex
substances which on hydrolysis yield Polyhydroxy
aldehyde or ketones
• Examples of carbohydrates are, Glucose,
sucrose,Starch, cellulose ,etc
By Asghar khan lecturer in Botany GDC Totakan
3. Classification of carbohydrates
• Classified into three groups
• 1. Monosaccharides
• 2. Oligosaccharides
• 3.Polysaccharides
• Monosaccharides
• Mono means one and Saccharide means sugar
• They are simple sugars
• They have Empirical formula (CH2O)n
• They Can not be further hydrolyzed into more
simple units
• They are Sweet in taste, easily soluble in
water and crystalline
4. MONOSACCHARIDES
• Contains either aldehyde or ketone group.
• The carbon backbone in monosaccharide
comprises of 3 to 7 carbon atoms
• Their names are ends with –ose, with 3 carbon
atoms are called trioses, with 4 carbon atoms
tetroses and with five carbon atoms are
Pentoses and so on.
• Most monosaccharide form a ring structure in
solution
6. OLIGOSACCARIDES
• Oligo means few, saccarides means sugar
• A saccharide polymer containing a small number (2 to 10)
of simple sugar (monosaccaride) linked through gylcosidic
bond.
• Those oligosaccharides which yield two monosaccahrides on
hydrolysis are called Disaccaride
• Three monosaccaride units are called trisaccharide
• Disaccharides
• Most common oligosaccaride
• Less sweet in taste, less soluble in water as compared to
monosaccharide
• Can be hydrolyzed into two monosaccharide units
By Asghar khan lecturer in Botany GDC Totakan
7. Disaccharides
• Example of Disaccharide
• Sucrose (cane sugar),Lactose (milk sugar) ,
Maltose (malt sugar, found in fruits)
• Glucose + Fructose synthesis Sucrose +water
• Glucose+ Glucose synthesis Maltose+ Water
• Glucose+ Galactose synthesis Lactose +water
8. Polysaccharides
• Complex carbohydrate
• Are polymers of monosaccharide unit
• Yields more than ten units of glucose on hydrolysis
• They are Tasteless, insoluble in water
• Examples of polysaccharides are
• Starch, Glycogen, Cellulose,Chitin etc
• a.Starch:
• Starch is a polymer of many glucose units.
• Starch is stored in plant cells
• Exists in two forms
• Amylose : unbranched chain of glucose units, more
soluble in water
• Amylopectin : Branched chain of Glucose units, less
soluble in water.
9. Polysaccharides
• b. Glycogen are called animal starch
• They are Polymer of Glucose units (monomers)
• Extensively Branched structure
• Stored in animal cells
• c. Cellulose
• Most abundant carbohydrate in nature
• Formed of unbranched chain of Glucose units
(monomers)
• Building material of plant cell wall
• Human digestive system can not digest cellulose
due lack of an enzyme called cellulase
• Cotton fiber is a pure example of cellulose
By Asghar khan lecturer in Botany GDC Totakan
11. Polysaccharides
• d.Chitin
• Chitin is a polysaccharide
• Found in exoskeleton of Arthropods, Fungal cell
wall
• Polymer of glucose & an amino group (-NH2) is also
attached to each glucose molecule
• Like cellulose chitin is also not digestible
12. Function of carbohydrates
• 1) Source of energy :
• Carbohydrates are used as source of energy.
• During respiration C-H bonds are broken down and
energy stored in these bond are release used in
various cell functions.
• 2) Storage molecules :
• They are stored in cell as reserve food for future
use
• 3) Structural building material :
• Cellulose is the major structural component of cell
wall in green plants while,
• Chitin is the structural component of exoskeleton of
Arthropods.
By Asghar khan lecturer in Botany GDC Totakan
