Micromolecules and Macromolecules?

Micromolecules and Macromolecules:

The molecules found in the cellular pool may be divided into two categories: Micromolecules and Macromolecules

A: Micromolecules:

The micromolecules are small in size and have low molecular weights ( i.e, less than 1000 daltons), simple molecular structure and often high solubility in the intracellular fluid. These include inorganic compounds such as water,mineral salt and gases, as well as organic compounds, namely, sugars, lipids, amino acids and nucleotides. The small molecules are the substrates and products of metabolism in the cell. The micromolecules act as buildings blocks for the macromolecules.



   In higher classes, you will learn about how to analyse a living tissue sample and identify particular inorganic elements, inorganic compounds and organic compounds. To analyse inorganic elements and compounds, weight a small amount of a living tissue ( e.g.,leaf or liver) and dry it. All the water is evaporated and the remaining material gives dry weight. Burn the tissue so that all the organic compounds are oxidized to gaseous form ( CO2 and water vapour) and are removed. The material left is termed ' ash' which contains inorganic elements ( e.g., calcium, magnesium etc.) .Inorganic compounds like sulphate, phosphate etc. can also identified in the acid__ soluble fraction.

          All organic compounds can also be extracted. These are then separated using appropriate separation techniques and finally purified.

B: Macromolecules:

The macromolecules are large in size, have high molecular weights( usually 10000 daltons and above), complex molecular structure and occur in colloidal state, being insoluble in intracellular fluid. They include only organic compounds, viz.,polysaccharides, proteins and nucleic acids.They are formed by polymerization of large  numbers of micromolecules. Macromolecules account for over 90% of the dry mass of cells. Lipid molecules may be large, but are usually not large enough to be considered macromolecules. 

Biochemical Similarity of Organisms:
The presence of the same organic compounds in approximately the same proportions in all living organisms points to a fundamental similarity between them. This is due to common origin of life. 

Differences between Micromolecules and Macromolecules ?


1) Are small in size.

2) Have low molecular weights.

3) Have simple structure. 

4) Occur as molecular solution in the intracellular fluid.

5) Form building blocks ( monomers) of macromolecules. 

6) Examples: inorganic compounds ( H2O, mineral salts, gases) as well as organic compounds ( sugars lipids, amino  acids, nucleotides). 


1) Are large in size.

2) Have high molecular weights.

3) Have complex structure. 

4) Occur as colloidal solution in the intracellular fluid. 

5) Formed by polymerization of micromolecules .

6) Examples: only organic compounds ( polysaccharides, proteins, nucleic acids).


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