Where do we get all our energy from and how? Not from the Middle East. Not via Tankers!

In this lecture you will learn photophosphorylation, photosynthesis, Adenosine, adenosine monophosphate, adenosine diphosphate, adenosine triphospahte, chlorophyll, glucose, glycogen, metabolism, respiration, xanthophylls, stomata, carotenoids.

We get all our energy from the sun. However, we cannot sit in the sun and get all the glucose/glycogen which we need for our metabolic processes. So we are fortunate in that all the green plants you see with your eyes are working for you and me. Read on for more details.

Figure A. Diagrammatic representation of photosynthesis

All green plants contain a substance called chlorophyll. Plants containing chlorophyll in their leaves and elsewhere can photosynthesize in the presence of sunlight and the following equation will take place at a molecular level.

The overall equation is: 6H2O + 6CO2 ———-> C6H12O6+ 6O2

Equation 1 Photosynthetic equation – discussed in detail below.

Six molecules of water combine with six molecules of carbon dioxide to give one molecule of sugar (carbohydrate) and six molecules of oxygen.

This reaction, photosynthesis, takes place in the green part of the plant called the chloroplast. The chloroplast is located in the leaf. Please see a cross section of the leaf in a standard text book or you can review the diagram below which is obtained from www.emc.maricopa.edu/faculty .

The practical relevance of this understanding is that green plants obtain water through their roots and carbon dioxide through their stomata from the immediate environment. Water and carbon dioxide are converted into glucose and oxygen both. Glucose and oxygen keep all the animals on the surface of this earth alive.

In plants, water enters the plant through the root cap of the root. From here it is transported up to the leaves by specialized cells known as xylem. All land plants must guard against drying out and often have specialized stomatal structures for this purpose. Carbon dioxide cannot enter the plant through the waxy leaf. It must enter the leaf through the stomata. Similarly, oxygen produced during photosynthesis must leave the leaf through the stomata.

We all know that chlorophyll is green, when we talk about chlorophyll we generally mean chlorophyll a. There are other types of chlorophylls which are not green. These are called accessory pigments and include chlorophyll b, c, d, and e, xanthophylls and carotenoids such a beta-carotene. Accessory pigments (chlorophylls) absorb energy which is not absorbed by chlorophyll a.

Chlorophyll a absorbs its energy from the intermediate (Green Yellow-Orange) wavelengths.

Figure B. Cross section of a leaf.

In equation 1, above we saw that 6 molecules of water combined with 6 molecules of carbon dioxide to give one molecule of sugar (carbohydrate) and six molecules of oxygen. This reaction takes place in the chloroplast. The chloroplast is a highly specialized cell. The structure of the cell is as given below.