● There is a `color{violet}("wide diversity in living organisms")` in our biosphere.

● If we perform such an analysis on a `color{violet}("plant tissue, animal tissue")` or a `color{violet}("microbial paste,")` we obtain a list of elements like `color{violet}("carbon, hydrogen, oxygen")` and several others and their respective content per unit mass of a `color{violet}("living tissue.")`

● If the same analysis is performed on a piece of `color{brown}("earth’s crust")` as an example of `color{violet}("non-living matter,")` we obtain a similar list.

● In absolute terms, `color{brown}("no such differences")` between the two lists could be made out.

● All the elements present in a sample of `color{violet}("earth’s crust")` are also present in a `color{brown}("sample of living tissue.")`

● However, a closer examination reveals that the relative abundance of `color{brown}("carbon and hydrogen")` with respect to other elements is higher in any living organism than in `color{violet}("earth’s crust.")`

● One can also find as to what type of `color{violet}("organic compounds")` are found in `color{violet}("living organisms.")`

● To get an answer, one has to perform a `color{brown}("chemical analysis.")`

● We can take any `color{brown}("living tissue")` (a vegetable or a piece of liver, etc.) and grind it in `color{brown}("trichloroacetic acid")` `(Cl_3C COOH)` using a `color{violet}("mortar and a pestle.")`

● We obtain a `color{violet}("thick slurry.")`

● If we were to `color{violet}("strain")` this through a `color{violet}("cheesecloth or cotton")` we would obtain two fractions.

● One is called the `color{brown}("filtrate")` or more technically, the `color{violet}("acid-soluble pool")`, and the second, the `color{brown}("retentate")` or the `color{violet}("acid-insoluble fraction.")`

● Scientists have found thousands of `color{violet}("organic compounds")` in `color{brown}("the acid-soluble pool.")`

● Then `color{violet}("one extracts")` the compounds, then subjects the extract to various `color{violet}("separation techniques")` till one has separated a compound from all other compounds.

● In other words, `color{violet}("one isolates")` and purifies a compound.

● `color{brown}("Analytical techniques")`, when applied to the compound give us an idea of the `color{violet}("molecular formula ")` and the probable structure of the compound.

● All the `color{violet}("carbon compounds")` that we get from `color{violet}("living tissues")` can be called `color{brown}("‘biomolecules’.")`

● However, `color{violet}("living organisms")` have also got`color{violet}(" inorganic elements")` and compounds in them.

● A slightly different but `color{violet}("destructive experiment")` has to be done.

● One weighs a small amount of a `color{violet}("living tissue")` (say a leaf or liver and this is called `color{brown}("wet weight")` ) and dry it.

● All the `color{violet}("water, evaporates.")`

● The remaining material gives `color{brown}("dry weight. ")`

● Now if the `color{violet}("tissue")` is fully burnt, all the `color{violet}("carbon compounds")` are `color{brown}("oxidised")` to gaseous form (`CO_2`, water vapour) and are removed.

● What is remaining is called `color{brown}("‘ash’.")`

● This ash contains `color{violet}("inorganic elements")` (like calcium, magnesium etc).

● `color{violet}("Inorganic compounds")` like `color{violet}("sulphate, phosphate")`, etc., are also seen in the `color{violet}("acid-soluble fraction.")`

● Therefore elemental analysis gives elemental composition of `color{violet}("living tissues")` in the form of `color{violet}("hydrogen, oxygen, chlorine, carbon")` etc. while analysis for compounds gives an idea of the kind of `color{violet}("organic and inorganic")` constituents present in `color{violet}("living tissues.")`

● From a chemistry point of view, one can identify `color{brown}("functional groups")` like `color{violet}("aldehydes, ketones, aromatic compounds")`, etc.

● But from a `color{violet}("biological point")` of view, we shall classify them into `color{violet}("amino acids, nucleotide bases, fatty acids")` etc.