Carbon Cycle Basics - Step II - CO2 Uptake, Storage, and Release

Low energy carbon dioxide (CO2) is available in the "normal" near Eaarth atmosphere in very small but reliable quantities, as of 2010 393 parts per million molecules per unit of measure (PPM). NOTE: Bill McKibben has renamed our planet - Eaarth - to reflect the changed situation we will soon face in this changed world.

Plants (and only plants- with a few exceptions) take in CO2 through holes in foliage to make energy storage compounds.  Other living things use this stored energy for all life processes (with a few exceptions*).

Plants use light energy to break up water (H2O) into 2 hydrogen atoms that are attached to a carrier and moved to another site where it can be combined with CO2.  The other part of the water, oxygen (O), is collected combined into a stable form (O2) and released back to the air as a waste product by this process.

This energy conversion (and most other Plant activities) happen inside special containers called cells.  Plant cells generally have two boundary structures, a strong cell wall made of cellulose and a membrane that controls the movement of water and compounds in and between cells.

The hydrogen, carbon and oxygen, (H from water, C & O from CO2) is formed in the absence of light into sugar (a carbohydrate, something that has C,O, & H) which is used throughout the plant.

Plants use sugar as a "currency"!  There are sugar savings accounts, there are sugar transport systems, there are sugar converters that change it into many different kinds of things, and there are sugar structures (wood cells, non-woody fibers (strong cells with no lignin), cell walls of non-fibrous plants, like algae).

Any sweet plant part is probably associated with some of those three kinds of cells.  The sweetness comes from the sugar that is present either as a building block or as a storage product in a "savings account", or is part of a compound that your body can

* We will drop the mention of these exceptions but they include some bacteria which are not technically plants.
Alan Page,
May 29, 2014, 6:13 PM