The Basic Needs For Photosynthesis

The Basic Needs For Photosynthesis

Plants, as well as some Protists and Monerans, can take small

molecules from the environment and bind them together using the energy

of light. The incoming light energy is transformed into the energy

holding the new molecules together, and the organisms use those

molecules as an energy "fuel." The basic process can be represented

this way:

CO2 + H2O light> C6H12O6 + O2

Carbon Dioxide Water (sugar) Oxygen

In the case of water organisms, the carbon dioxide and water are from

their immediate surroundings; for most land plants, the water is

absorbed from the soil and the carbon dioxide from the atmosphere.

The glucose is used for two major purposes: 1) it serves as an energy

reserve for periods of darkness (don't forget that photosynthesizers,

like any living things, require energy and get it through respiration

processes, commonly aerobic respiration, and 2) it is used as a major

component of structure: the cell walls that surround almost all

photosynthetic cells are made of starches, huge molecules made up of

hundreds, commonly thousands, of sugar molecules bound together. This

is why plant fibers are great sources of nutrition if you can break

them down, which is difficult - we humans can't, being limited to the

simpler starches put into seeds and fruits and tubers as accessible

energy stores.

Keep in mind that photosynthetic organisms are still living things,

with protein-based chemistry, which means that they have nutritional

requirements beyond carbon dioxide and water. Proteins, unlike sugars

and starches, contain a significant amount of nitrogen, which usually

needs to be absorbed as nitrates (a nitrogen-oxygen molecule) to be

usable. The production and use of glucose for energy also requires ATP

as an energy carrier; ATP contains phosphorus, usually absorbed as

phosphates (a phosphorus-oxygen molecule). Anyone who takes care of

plants knows that nitrates and phosphates are important ingredients in

fertilizers. Most photosynthesizers have a few critical molecules that

contain other materials as well, such as iron, or need small ions,

such as sodium, for some of their chemical processes.