Photosynthesis

Light Harvesting Complexes and their effects on photosynthesis

Michael Davis

Excelsior College

Abstract

This paper explores the results from research conducted on wild bacteria and the effects between the presence and absence of light harvesting complexes (LHC’s I, II) and the reaction center (RC). During these experiments a mutant gene would affect one of the three genes required for photosynthesis. Each one of the genes LCH-I, LHC-II and RC had a different outcome when their particular gene was mutated.

Typically, ‘light is absorbed by the light harvesting complex II (LHC-II) antenna. LH-II then transfers its energy to the nearby protein Light Harvesting Complex I (LH-I), which also absorbs light itself. LH-I then passes on the energy to a protein called the Reaction Center (RC), which is directly surrounded by LH-I forming the so-called LHI-RC complex. The RC, along with other proteins, then use this energy to facilitate a charge separation across the membrane. The two main light harvesting complexes are LH2 and LH1 and their function is to absorb light energy from the sun and transfer that energy to the reaction center. LH1 (light – harvesting complex I) which surrounds the reaction center (RC) in a 1:1ration; the two are often thought of as one unit; the LH1-RC complex” (Case Study: Light Harvesting Complex II,2013) During the experiments, mutants where either LHC1 or LHC2 were not working right still produced quite a bit of growth. However, in the mutant where the RC was not working right, we see almost no color growth in the light.

The difference between LHC-I and LHC-II is that “LH1 is a constant feature, being directly associated with the reaction centre, whereas the amount of LH2, and indeed its spectral properties, vary according to growth conditions and light intensity. LH1 is therefore frequently referred to as the core or inner antenna, whereas LH2 is known as the peripheral or variable antenna” (Structure and function of...