Is photosynthesis irreducibly complex ?
“The process of photosynthesis is a very complex set of interdependent metabolic pathways “How it could have evolved is a bit mysterious.”
Robert Blankenship, professor of biochemistry at Arizona State University
The process of photosynthesis is arguably the most important chemical reaction on Earth that has led to the development of advanced life forms.
The main source for food and oxygen are cyanobacteria and chloroplasts that do photosynthesis. Cyanobacteria are essential for the nitrogen cycle, and so to transform nitrogen in the atmosphere into useful form for organisms to make the basic building blocks for life. The end product of photosynthesis is glucose, - needed as food source for almost all life forms. For a proponent that life took millions of years to emerge gradually and biodiversity as well, and so cyanobacteria and chloroplasts, that came hundreds of millions of years after life started, that is a huge problem. No oxygen in the atmosphere and UV radiation would kill the organisms. Nor could they emerge without an adequate food source. Looking everything in that perspective, it makes a lot of sense to believe God created everything in six days. And created the atmosphere with oxygen, and the nitrogen cycle fully setup, and plants and animals like cyanobacteria, essential in the food chain and nitrogen cycle. That would solve the - problem of nutrition, - the problem of UV radiation - and the problem of the nitrogen source required for life.
The existence of the same organism of cyanobacteria of two conflicting metabolic systems, oxygen-evolving photosynthesis, and oxygen-sensitive nitrogen fixation, is a puzzling paradox. Explanations are pure guesswork.
Researchers have long been puzzled as to how the cyanobacteria could make all that oxygen without poisoning themselves. To avoid their DNA getting wrecked by a hydroxyl radical that naturally occurs in the production of oxygen, the cyanobacteria would have had to evolve protective enzymes. But how could natural selection have led the cyanobacteria to evolve these enzymes if the need for them didn’t even exist yet? The explanations are fantasies at best.
In photosynthesis, 26 protein complexes and enzymes are required to go through the light and light independent reactions, a chemical process that transforms sunlight into chemical energy, to get glucose as an end product, a metabolic intermediate for cell respiration. A good part of the protein complexes is uniquely used in photosynthesis. The pathway must go all the way through, and all steps are required, otherwise, glucose is not produced. Also, in the oxygen-evolving complex, which splits water into electrons, protons, and CO2, if the light-induced electron transfer reactions do not go all the five steps through, no oxygen, no protons and electrons are produced, no advanced life would be possible on earth. So, photosynthesis is an interdependent system, that could not have evolved, since all parts had to be in place right from the beginning. It contains many interdependent systems composed of parts that would be useless without the presence of all the other necessary parts. In these systems, nothing works until all the necessary components are present and working. So how could someone rationally say, the individual parts, proteins and enzymes, co-factors and assembly proteins not present in the final assemblage, all happened by a series of natural events that we can call ad hoc mistake "formed in one particular moment without the ability to consider any application." , to then somehow interlink in a meaningful way, to form electron transport chains, proton gradients to " feed " ATP synthase nanomotors to produce ATP, and so on? Such independent structures would have not aided survival. Consider the light harvesting complex, and the electron transport chain, that did not exist at exactly the same moment--would they ever "get together" since they would neither have any correlation to each other nor help survival separately? Repair of PSII via turnover of the damaged protein subunits is a complex process involving highly regulated reversible phosphorylation of several PSII core subunits. If this mechanism would not work starting right from the beginning, various radicals and active oxygen species with harmful effects on photosystem II (PSII) would make it cease to function. So it seems that photosynthesis falsifies the theory of evolution, where all small steps need to provide a survival advantage.
Essential parts of oxygenic photosynthesis
The light reactions
1. Lipid bilayer membranes are critical to the early stages of energy storage, such that photosynthesis must be viewed as a process that is at heart membrane-based. 4
2. Chlorophyll is an essential component of photosynthesis, which helps plants get energy from light. 1
3. The light-harvesting complexes, also called antenna complexes, are essential for collecting sunlight and regulating photosynthesis 2
4. Photosystem II (PSII) is a key component of photosynthesis 2
4a.The reaction center is the key component for the primary events in the photochemical conversion of light into chemical energy. 19
5. The oxygen-evolving complex is responsible for catalyzing the oxidation of water to molecular oxygen in plants, algae, and cyanobacteria. 3
6. Of these essential redox components, tyrosine, P680, pheophytin, QA, and Qj have been shown to be bound to two key polypeptides (Dl and D2) 8
7. If the oxidation of plastoquinone takes place in the cytochrome b6 f complex that is located in the stroma, then the plastoquinone must diffuse within the lipid bilayer from the grana membranes to the stromal membranes. In
either case, a long-distance diffusion process is necessary to complete the traversal of the electron transport chain.
8 The cytochromeb6 f complex is an essential player in noncyclic and cyclic electron flow 4
9) Plastocyanin is an essential member of photosynthetic electron transport and functions near PS I. 5
10 PSI is necessary to provide the energy to reduce NADP+ to NADPH 6
10a.The reaction center is the key component for the primary events in the photochemical conversion of light into chemical energy. 19
11) Ferredoxin (Fd) proteins are required for the electron transfer process from the bound Fe–S centers in the Photosystem I reaction center to NADP+. 4
12) Ferredoxin—NADP(+) reductase is an essential member of photosynthetic electron transport and functions near PS I.
13) ATP synthase is essential in plants for solar energy conversion and carbon fixation.
The dark or light independent reactions
14) Rubisco is essential for the photosynthetic process.
15) Phosphoglycerate kinase is required to catalyse the phosphorylation of 3-PGA by ATP 10
16) Glyceraldehyde-3-phosphate dehydrogenase (NADP+) (phosphorylating) is essential to catalyse the reduction of 1,3BPGA by NADPH 10
17) Triosephosphate isomerase is needed to catalyze the reversible interconversion of the triose phosphate isomers dihydroxyacetone phosphate and D-glyceraldehyde 3-phosphate. 11
18) Fructose-bisphosphate aldolase is a key enzyme to catalyze a reversible reaction that splits the aldol, fructose 1,6-bisphosphate, into the triose phosphates dihydroxyacetone phosphate (DHAP) and glyceraldehyde 3-phosphate (G3P). 12
19) Transketolase catalyzes the conversion of sedoheptulose-7-P and glyceraldehyde-3-P to pentoses, the aldose D-ribose-5-P and the ketose D-xylulose-5-P. 13
20) Aldolase performs an aldol reaction (creating an aldol) or its reverse (cleaving an aldol). 14
21) Sedoheptulose-bisphosphatase catalyzes the removal of a phosphate group from sedoheptulose 1,7-bisphosphate to produce sedoheptulose 7-phosphate. 15
22) Transketolase catalyzes the reverse reaction, the conversion of sedoheptulose-7-P and glyceraldehyde-3-P to pentoses, the aldose D-ribose-5-P and the ketose D-xylulose-5-P. 16
23) Ribose-5-phosphate isomerase (Rpi) is an enzyme that catalyzes the conversion between ribose-5-phosphate (R5P) and ribulose-5-phosphate (Ru5P). 17
24) Phosphoribulokinase catalyzes the chemical reaction ATP + D-ribulose 5-phosphate \rightleftharpoons ADP + D-ribulose 1,5-bisphosphate
4) Blankenship: Molecular mechanisms of photosynthesis
8 Concepts in Photobiology: Photosynthesis and Photomorphogenesis page 26
9) Handbook of Plant and Crop Physiology, Third Edition page 394
Cyanobacterias, amazing evidence of design
Why the biosynthesis pathway of Chlorophyll must be intelligently designed
The oxygen evolving complex (OEC) of photosystem II is irreducible complex.
The earth's atmosphere
Rubisco's amazing evidence of design
Last edited by Admin on Sat Aug 03, 2019 7:22 am; edited 2 times in total