TABLE OF CONTENTS

TITLE PAGE        –         –         –         –         –         –         –         –         i

CERTIFICATION           –         –         –         –         –         –         –         ii

DEDICATION      –         –         –         –         –         –         –         –         iii

ACKNOWLEDGEMENTS       –         –         –         –         –         –         iv

TABLE OF CONTENTS          –         –         –         –         –         –         v-vi

CHAPTER ONE

1.0 INTRODUCTION – –         –         –         –         –         –         1

CHAPTER TWO

2.0 DISCOVERY OF CHEMOSYNTHESIS –         –         –         4

2.1     Evolution of Photosynthesis      –         –         –         –         –         6

2.1.1  Symbiosis and the Origin of Chloroplasts      –         –         –         7

2.1.2  Photosynthetic Eukaryotes Lineages    –         –         –         –         9

2.1.3  Cyanobacteria and the Evolution of Photosynthesis          –         10

2.2     Factors Affecting Photosynthesis        –         –         –         –         11

2.2.1  Light Intensity, Wavelength and the Temperature   –         –         11

2.2.2  Carbondioxide Level and Photorespiration    –         –         –         13

2.3     Order and Efficiency of Photosynthesis         –         –         –         16

CHAPTER THREE

3.0     Photosynthetic Membranes and Organelles   –         –         –         17

3.1     Light Dependent Reactors of Photosynthesis           –         –         20

3.1.1  Z scheme     –         –         –         –         –         –         –         –         22

3.1.2  Water Photolysis   –         –         –         –         –         –         –         26

3.2     Light Independent Reactions of Photosynthesis       –         –         28

3.3     Hydrogen sulfide chemosynthesis Process     –         –         –         34

3.4     Differences Between Chemosynthesis and Photosynthesis  –       35

CHAPTER FOUR

4.0     SUMMARY AND CONCLUSION

4.1     Summary     –         –         –         –         –         –         –         –         39

4.2     Conclusion  –         –         –         –         –         –         –         –         40

References

CHAPTER ONE

1.0 INTRODUCION

In biochemistry, chemosynthesis is the biological coversion of one or more carbon-containing molecules (usually carbospoxide or methane) and inorganic compounds (e.g hydrogen gas, hydrogen sulfide) or ferrous ions as a source of energy, rather than sunlight, as in photosynthesis. Chemoautotrophs organisms that obtain carbon from carbondioxide through chemosynthesis are phylogeneticallydiverse,but also groups that include conspicuous or biogeochemically important taxa include the sulfur oxidizing gamma and epsilon proteobacteria, the Aquificae, the methanogenicarchaea and the neutrophilic iron-oxidizing bacteria. Many microorganisms in the ark regions of the oceans use chemosynthesis to produce biomass from single carbon available, the energy available from reaction between CO₂ and H₂O (leading to production of methane, canbe large enough to drive the production of biomass. Alternatively, from reactions in which substances such as hydrogen sulfide or ammonia are oxidized (Bryant and Frigaard, 2006). This may occur with or without oxygen. It has been hypothesized that anaerobic that anaerobic chemosynthesis may support life below the surface of Mars, Jupiter’s moon Europa and other planets (Bryant and Frigaard, 2006).

Photosynthesis is a process that changes sunlight into chemical energy, split water to liberate O₂ and fixes CO₂ into sugars. Photosynthetic organism arephototrophs, which means that they are able to synthesize food directly from carbon dioxide and water using energy from light. However, not all organisms use carbon dioxide as a source of carbon atoms to carry out photosynthesis. Phototrophs  use organic compounds, rather than carbondioxide as a source of carbon (Bryant and Frigaard, 2006). In plants, algae and cyanobacteria, photosynthesis releases oxygen. This is called oxygenic photosynthesis and is by far the most common type of photosynthesis sued by living organisms. Although there are some differences between oxygenic photosynthesis  plant, algae and cyanobacteria, the overall process is quite similar in these organisms. There are also many varieties of an oxygenic photosynthesis, used mostly by certain types of bacteria, which consume carbon dioxide but do not release oxygen (Bryant and Frigaard 2006).