Biomolecules of life ( Carbohydrate )

Subject: Biology

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This note provides information about biomolecules and carbohydrate with is types, features, and importance.concept of carbohydrate.

Biomolecules of life ( Carbohydrate )

Biomolecules of Life

Biomolecules are the molecules that occur naturally in living organisms. It includes macromolecules like protein, carbohydrates, lipids, and nucleic acids and also micro molecules like primary and secondary metabolites and natural products, Living cells consists of both organic and inorganic components which are of two kinds.

  1. Organic compounds: Carbohydrates, Proteins, Fats, and Nucleic acids.
  2. Inorganic compound: Water, Minerals, and Salts.





Essential biomolecules which are compounds of carbon, hydrogen, and oxygen where hydrogen and oxygen occur in a ratio of 2: 1, so known as "hydrates of carbon".
General formula = Cn( H2O )n
They have free aldehyde or ketone group. Carbohydrate-containing aldehyde group ( -CHO- ) are called aldoses and ketone group ( - C = O ) are called ketoses.

Categories of Carbohydrates.

Categories of carbohydrates
fig:Categories of carbohydrates

They are divided according to the complexity of chemical substances of which they are formed.


  • Simplest forms of carbohydrate.
  • Cannot be hydrolysed.
  • Highly soluble in water and sweet in taste.
  • Simple sugars are made up of polysaccharides compounds.All the carbon atoms have a hydroxyl group ( - OH -) attached except one where either an aldehyde ( - C = O ) group is attached.
  • Sugar with aldehyde group are aldoses and ketone group are ketoses.
  • Are also known as reducing sugar as free aldehyde and ketone group can reduce Cu++and Cu+ form.
  • A compound of 3 -7 carbon atoms.
  • Examples are glucose, fructose, and galactose.



Trioses C3H6O3(3carbon atoms)

Eg: Dihydroxyacetone Glyceraldehyde.


C4H8O4 (4 carbon atoms)

Eg: Erythrose, Threose.
Pentoses C5H10O5 (5 carbon atoms) Eg; Ribose, Deoxyribose.
Hexoses C6H12O6 (6 carbon atoms)

Eg: Glucose, Fructose andGalactose.

Heptoses C7H14O7(7 carbon atoms) Eg; Sedoheptulose.

Glucose or aldohexose ( C6H12O6) is the most abundant monosaccharides with 6 carbon atoms and 5 hydroxyl group and one aldehyde group. It is white, crystalline, sweet testing, and water soluble.

Glucose (ring)
fig:Glucose (ring)

Glucose open chainGlucose open chain fructose

fructose (open chain)
fig:(open chain)
Galactose(open chain)
fig:Galactose(open chain)



  • Contains 2 - 10 molecules of monosaccharides.
  • Monosaccharides are joined by glycosidic linkage.
  • On hydrolysis yields monosaccharides.
  • Simplest oligosaccharide is disaccharides.
  • General formula - C12O22O11.
  • Eg: sucrose, lactose, and maltose.


Oligosaccharides Composition Examples
Disaccharides 2 monosaccharide molecules Sucrose,Maltose,Lactose
Trisaccharides 3 monosaccharide molecules Mannatriose,Raffinose,Rabinose
Tetrasaccharides 4 monosaccharides Scorodoes,Stachyrose





  • Simplest oligosaccharides formed of 2 molecules of monosaccharides that are joined by glycosidic linkage.
  • Gives monosaccharides on hydrolysis.
  • Water soluble and sweet in taste.
  • Reducing sugars are maltose and lactose, and non-reducing sugar is sucrose.
  • Eg; Maltose, Lactose, Sucrose

    Glucose + glucose = Maltose
    Glucose + Galactose = Lactose
    Glucose + Fructose = Sucrose



  • The complex molecule formed by condensation of a large number of monosaccharides.
  • Monosaccharides are joined by glycosidic linkage.
  • On hydrolysis gives monosaccharides.
  • Water insoluble and not sweet in taste.
  • Eg; Starch( plants), cellulose ( plant cell wall ), glycogen ( animals ) and dextrin.

Functions of Carbohydrate

  • 60% of total energy is provided by carbohydrates.
  • Acts as a building blocks.
  • Help in the synthesis of fats and amino acids.
  • Acts as a reserve food like starch and glycogen.
  • Forms structural components in RNA and DNA like ribose and deoxyribose sugars.




Things to remember
  • Biomolecules are the molecules that occur naturally in living organisms.
  • Living cells consist of both organic and inorganic components.
  • Three types of carbohydrates are monosaccharides, oligosaccharides and polysaccharides.
  • Glucose or aldohexose is the most abundant monosaccharides.
  • Most common and  simplest oligosaccharide is the disaccharide.
  • Carbohydrate functions as an energy source, building blocks, structural components, and reserve food. 
  • It includes every relationship which established among the people.
  • There can be more than one community in a society. Community smaller than society.
  • It is a network of social relationships which cannot see or touched.
  • common interests and common objectives are not necessary for society.

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