Photosynthesis: The Role of Light - Essay Example

Morphology of the plant leaf The morphology of the leaf encompasses upper and lower epidermis- the outer later, possessing minute openings called the stomata through which gaseous exchange (CO2 is taken in and O2 is given out of the leaf), as well as elimination of water takes place through stomata (transpiration). Between these two layers is a layer of mesophyll cells they could be compact or spongy (filled with air) depending upon the plant adaptation to its habitat. Vascular bundle(s) are present inside the leaf.

They have vascular tissues xylem (to carry water and minerals from the roots to the leaf) and phloem (to carry prepared food to the different plant parts and also to the storage parts such as fruits and stem or roots depending on the plant). The epidermis, both upper and lower do not contain chloroplast and therefore no photosynthesis takes place in these set of cells. They provide protection to the inner cells of the leaf (“Photosynthesis”). Structure of Chloroplast Mesophyll cells contain the organelle chloroplast, a typical characteristic feature of the plants, it contains outer membrane, inner membrane, stroma- the space, thylakoids- disc like structure, stacked one above the other to form a structure called grana (“Photosynthesis”). . Light Reaction B.

Dark Reaction. A. Light Reaction- occurs in the presence of light and hence it is Light Dependent Reaction. During the process a molecule of chlorophyll in the thylakoids, absorbs a photon of light and eliminates an electron. Various other pigment molecules such as ?- carotene form a cluster and play an imperative role in absorbing a different color of light spectrum and pass the energy to the chlorophyll molecule (the elimination of hydrogen (H) atoms from the water molecule). The electron travels through the ETC (electron transport chain), during the process ATP (Adenosine triphosphate), an energy molecule is produced as well as NADP+ is reduced to NADPH.

As a result of this reaction water molecule splits into H+ and O2 is released. The reaction is: 2H2O + 2 NADP+ + 3 ADP + 3 Pi + light > 2 NADPH + 2 H+ + 3 ATP + O2 (“Understanding The Role of Light in Photosynthesis”). Light Reaction Hydrogen molecule is made up of an electron (e-) as well as a proton (H+). With the help of light energy water molecule split as 2H2O > 4e- + 4H+ + O2. The released electron reduces NADP+ to NADPH to be used in Dark Reaction as well as it onsets an electrochemical charge to give energy for the proton pumping form stroma (the matrix of the chloroplast) to the thylakoid.

These protons on one hand reduce NADP+ to NADPH and on the other hand they flow reverse from the thylakoid to stroma and during the process the energy given put is utilized by the ADP molecule to undergo the process of phosphorylation to form ATP, an energy rich molecule. Since the process of phosphorylation takes place in the presence of light it is