My biology book states

"life on earth depends upon carbon based molecules, most of these food sources are also carbon based. Depending upon the complexity of these carbon sources, different organisms can then use different kinds of nutritional processes"

Please explain this statement.

  • $\begingroup$ They mean complex arrangement of the carbon atoms in the carbon sources. $\endgroup$ – JM97 May 17 '17 at 12:48
  • $\begingroup$ According to me Plants are autographs and they make their own food by the process called photosynthesis and they take Carbon dioxide and water directly from air and roots so Thor the simple diffusion is taking place so they are not that much complex than us so they use simple nutritional process $\endgroup$ – Tanushka Jun 24 '17 at 16:14
  • $\begingroup$ @Tanushka - On Stack Exchange we are looking for informed answers supported by citations, references or links. This allows users of the site to judge their validity. Please read the tutorial before posting or answering. $\endgroup$ – David Jun 24 '17 at 16:37

Consider all the different types of carbon molecules one can find on earth.

Proteins. Sugars like cellulose and starch. Alkanes like methane and tar. CO2. Alcohols. A boatload of variety.

Now think of how each one is used or can be used by an organism. I will chow down on a potato. And some alcohol. Termites eat cellulose. Anaerobic bacteria use methane. Plants eat up the CO2.

One carbon nothing eats is CaCO3 or limestone. I am not sure why. Oh - also diamond. Not many things can metabolize a diamond. Although maybe they don't get the opportunity to try...

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  • $\begingroup$ Have in mind that CaC03 and diamond (as well as graphite, nanotubes, carbonic acid, cyanides, carbon dioxide etc) are inorganic compounds, despite having carbon (actually, diamond is not even a compound, but just an allotrope of C). $\endgroup$ – user24284 May 18 '17 at 1:56
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    $\begingroup$ @gerardo Furtado CO2 is also technically an inorganic compound. But lots of things use it. "Complexity of carbon sources" I think encompasses traditional concepts of inorganic and organic. $\endgroup$ – Willk May 18 '17 at 12:52
  • $\begingroup$ Consider that all the various carbon compounds mentioned can react with oxygen (perhaps including other things in the reaction) to produce energy and CO2. CO2, OTOH, requires energy from sunlight for plants to turn it into more complex carbon compounts. Simplistically, CaCO3 is like CO2 in that it would require energy to metabolize, but most of it sinks to the ocean floor where there's not a lot of sunlight. $\endgroup$ – jamesqf Jun 24 '17 at 18:08

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