11 of 29

Write now Article Tools

Vegetables use the photosynthesis to normally perform a reaction, the synthesis of carbohydrates from little and simple molecules (H2O and CO2), that we humans can't reproduce in any way in our laboratories; this shows that the creative fantasy of Nature is infinite, able to resolve every biological problem.

The first problem for vegetables is the production of the necessary fundamental fuels for their metabolic needs: these are glucose (C6O6H12) and fructose (C5O5H10), synthesized from very simple reagents, CO2, absorbed from the air, and H2O, from the soil.

Starch and cellulose are natural polymers of these two molecules, but only starch is used as energy source, mainly by seeds for feeding new plants; instead, cellulose has the structural function of making rigid vegetables' tissues by forming wood, leaves, seeds and fruits skin.

The fascinating feature of photosynthesis is that glucose and fructose are rather complex and particular molecules for their structure and I'm sorry I can't draw them on this site for Chemistry students, only limiting myself to write their raw formulas, as reported above.
Glucose synthesis is very complex and it needs a lot of energy and the work of many specific enzymes that drive the overall reaction (the sum of many intermediate reactions) just towards a precise direction, with an impressive yield of 100%.

The energy needed is provided by the "chlorophyll", a complex green pigment with a Mg++ ion in its centre, contained in the leaves of all plants and algae.
This molecule absorbs the energy photons by solar light, reaches an excited state and immediately abandons it using this energy to break the H2O, to release its O2 directly in the atmosphere and to provide electrons and energy for the synthesis of the energy-carrying molecules of ATP (Adenin TriPhosphate).
The ATP is the main energy carrier of living beings and it makes the H+ available for the production of NADPH (Nicotin Adenin DiPhosphate Hydrogenated), a reducing molecule because source of H+ ions.

In the reality, what we call chlorophyll is formed by 2 distinct molecules: the A-chlorophyll and the B-chlorophyll that, together, can absorb the light of the whole spectrum of visible light (400-750 nm of wavelength).
This is the first phase of the photosynthesis, the "luminous phase".

At this point, the "dark phase" follows, with the effective synthesis of the glucose; other H2O molecules are broken and the CO2 absorbed by leaves is reduced in many steps (Calvin's cycle), with

• 1
• 2
• next page >>

Add your voice

Know something about How photosynthesis works?
We want to hear your view. Write now!