Man's physical universe

xanabras

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PHOTOSYNTHESIS STORES ENERGY 721

tree adds the amount of wood in an ordinary broomstick to its size

every day.

The active material in the chloroplasts is a mixture of a bluishgreen

pigment, "chlorophyll a," and a green pigment, "chlorophyll b."

These pigments are magnesium compounds of very complex structure.

The empirical formula for "chlorophyll a" is C55H7205N4Mg.

Chlorophyll is always associated with at least twelve other yellow and

orange-red and sometimes red-brown pigments.

In some way or other

this mixture of pigments through the influence of light activates the

carbon dioxide molecules with the result that they will react with

water to form carbohydrates.

All Living Matter Is Probably Dependent on Photosynthesis.

All of the compounds in plants are believed to be produced indirectly

by photosynthesis. Animals cannot synthesize their own foods but

depend upon plants or other animals for sustenance. In the end every

animal is directly or indirectly dependent on plants for its food.

It is believed that a simple carbohydrate,^ such as glucose or fructose,

is the first product formed in photosynthesis. This simple carbohydrate

then polymerizes, i.e., several molecules unite to form

large molecules.

Starch and possibly such intermediate products as

sucrose (cane sugar), dextrinS; and gums may then be formed by the

polymerization of the simple sugars. Cellulose is a still more complex

compound — or, rather, mixture of compounds — produced by still

further polymerization.

Animals cannot utilize carbon or the hydrocarbons because they

cannot oxidize them. The reason for this probably lies in the equal

sharing of electrons by the various atoms.

Alcohols represent hydrocarbons

in which at least one pair of electrons has been partially displaced

from the carbon atoms and are therefore more readily oxidized.

H—C—

First stage

in oxidation

Second stage

in oxidation

H H O

H

H—C—O—

H—

II

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