Photosynthesis in Plants

The amount of water available will affect the rate of photosynthesis because if the plants do not have enough water, stomata will be shut and plants will be deprived of carbon dioxide.

Only the autotrophs can perform photophosphorylation. It means electrons once emitted from photsystem 1(P 700) returns back to it after passing through a series of electron carriers, in an electron transport system. A P700 molecule is a pigment, which can absorb the sunlight of wavelength, around 700 nanometer.

Chlorophyll is the molecule that traps this 'most elusive of all powers' - and is called a photoreceptor. It is found in the chloroplasts of green plants, and this is what makes,  green plants, green. The basic structure of a chlorophyll molecule is a porphyrin ring, co-ordinated to a central atom, Mg. This is very similar in structure to the heme group found in hemoglobin, except that in heme, the central atom is iron, whereas in chlorophyll,  it is magnesium.

The absorbed energy is used in splitting the water molecule, into the two components (Hydrogen and Oxygen) and releasing electrons. The free molecular oxygen is given out as a by-product and the energy of electrons, is used to add one inorganic phosphate to ADP to form ATP whereas, the H⁺ ions are picked by NADP⁺ which is reduced to NADPH.

Chlorophyll, the green pigment common to all photosynthetic cells, absorbs all wavelengths of visible light, except green, which it reflects, to be detected by our eyes.

The hydrogen ions also called protons, are made available by splitting up of water. Non-cyclic photophosphorylation needs a constant supply of water molecules. The net result of non-cyclic phosphorylation is the formation of oxygen, NADPH and ATP molecules. Oxygen is produced, as a waste product of photosynthesis.

Carbon dioxide, either in the atmosphere or in solution in surface waters, is the major source of carbon for living organisms. It is converted to organic form, by the autotrophs, which use it as sole carbon source. The most important in this conversion, are the photosynthetic autotrophs (seed plants on land and algae in water) that carry out oxygen producing type of photosynthesis.

Photosynthetic phosphorylation or photophosphorylation is the process of phosphate group transfer into ADP to synthesize energy rich ATP molecule making use of light, as external energy source. Down flow of protons from high to low concentration along H⁺ conc. gradient through ATPase complex, provides the energy that allows an ATP synthase enzyme, to produce ATP from ADP + Pi

The material within the chloroplast, is called the stroma. It contains one or more molecules of small circular DNA. It also contains ribosomes, however most of its proteins, are encoded by genes contained in the host cell nucleus, with the protein products, transported to the chloroplast. The enzymes necessary for carbon fixation, occur in the stroma of the chloroplast.

Photosynthetic phosphorylation or photophosphorylation is the process of phosphate group transfer into ADP to synthesize energy rich ATP molecule making use of light, as external energy source. Down flow of protons from high to low concentration along H⁺ conc. gradient through ATPase complex provides the energy, that allows an ATP synthase enzyme, to produce ATP from ADP + Pi

The energy released in chemical reactions is known as chemical energy. Energy can also be stored in matter as chemical energy which depends on how the particles of matter are arranged. Therefore, chemical energy depends on the positions of objects and is a form of potential energy.

O₂ gas is the by product being produced during photosynthesis . It can only pass out of the leaf through the opened stomata.

Chloroplasts are specialized organelles, found in all higher plant cells. These organelles contain the plant cell's chlorophyll, hence provide the green color. They have a double outer membrane. Within the stroma are other membrane structures - the thylakoids and grana (singular = granum) where photosynthesis takes place.

Light strikes photosystem-2 by exciting the electrons. The electron comes from a water molecule that has been split into hydrogen and oxygen. The excited electrons then travel down a short electron transport chain, and while doing so, they pump H⁺ into the inner thylakoid space across the thylakoid membrane from the stroma. The electrons are then passed, at the end of the transport chain, to photosystem 1, where they are re-excited by light.

The light reaction happens in the thylakoid membrane and converts light energy to chemical energy. This chemical reaction must take place in the light.