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This article was originally published as a chapter in the book “Design and Catastrophe: 51 Scientists Explore Evidence in Nature"
As students of science, we are impressed with the beauty and orderliness of creation. Personally, I have always been fascinated by the beauty, color, and intricate anatomy of leaves, recognizing in them the handiwork of the Master Designer.
Photosynthesis can be defined as the physicochemical process by which photosynthetic organisms use light energy to drive the synthesis of organic compounds.[1] The size, shape, color, thickness, and position of leaves on a plant are all significant for the process of photosynthesis. Various studies have shown that morphological and anatomical features of leaves as well as their orientation show a functional relationship with photosynthesis. For example, broad leaves tend to have larger petioles and veins and, hence, increased supply of water for photosynthesis, whereas thin laminar leaves reduce distance for diffusion of carbon dioxide and oxygen. Presence of a waxy cuticle and epidermal hairs affect the amount of sunlight absorbed, and plants in shady habitats show bicoloration, with sides of leaves not facing the sun lighter in color, enhancing the trapping of light.[2]
Under the microscope, we see in the epidermal layer of a leaf the symmetry of guard cells that make up the stomata that regulate the exchange of gases. Chloroplasts in the guard cells contain complex chlorophyll molecules essential for photosynthesis. It takes 17 enzymes to synthesize chlorophyll.[3] The lack of any one of these enzymes would prevent chlorophyll from being produced. Chlorophyll is responsible for the green color in plants and is made up of atoms arranged in a way that traps light energy.
The light-dependent stage of photosynthesis involves Photosystems I (P 700) and II (P 680), which are pigment molecules in the thylakoid membranes of chloroplasts. They are responsible for capturing photons of light energy and directing them to the reaction center for carbon fixation in what is known as photophosphorylation. The P 680 molecule is excited, and electrons are transferred to acceptors and down the electron transport system, losing energy in the process. This activates proton pumps in the thylakoid resulting in an H+ gradient, causing the enzyme ATP synthase to produce adenosine triphosphate (ATP). In P 700 the primary acceptor is different, and electrons are transferred to nicotinamide adenine dinucleotide phosphate (NADP+), which combines with an H+ forming NADPH, which reduces CO2 to glucose.
The light-independent reactions use this energy to reduce carbon dioxide to produce glucose in a process called the Calvin cycle. The three steps in the Calvin cycle are fixation, reduction, and regeneration. ATP from the light reaction is used to bind CO2 to ribulose 1,5-biphosphate (RuBP). Phosphoglycerate with the help of NADPH gets reduced to phosphoglyceraldehyde, which regenerates RuBP. Plant cells that perform the light and dark reactions of photosynthesis produce six carbon molecules in just 30 seconds. This is a simple view of a complex process working in perfect harmony.[4]
Complex organic molecules are built from atmospheric carbon dioxide, and no matter how hard scientists have tried to replicate this technology in the laboratory, they have failed to match the ingenious machinery in plants. No incomplete intermediate system has been able to produce glucose or direct the precise enzymes required at each step. Could such a process have gradually developed with small changes by natural selection?
The 11 enzymes in the Calvin cycle perform their duties in sequential steps resulting in a number of intermediates in the process, and these, in effect, have no other metabolic function. If any of these enzymes were missing, the whole chain of reactions would be disrupted. Chance could result in cell destruction if only enzymes were present and substrates were not at the right place for enzymatic reactions. Based on the extensive knowledge that we have of this system, the statistical probability that these enzymes could have been produced to react with such precision in a stepwise evolutionary process over supposed millions of years is unfathomably small. Intelligent planning and design at the time of Creation would be essential to ensure that the complex process accurately accomplishes its purpose.
God programmed chloroplasts to convert sunlight into chemical energy in an orderly, assembly line fashion by the process of photosynthesis. However, what strikes me as even more amazing is that by manufacturing glucose, photosynthesis becomes essential to sustain animal life, because the breaking down of glucose to provide energy through respiration releases oxygen. This nonstop production, together with animal consumption of seeds, fruits, flowers, roots, and leaves, makes all complex metabolic activities in animals dependent on the energy produced by autotrophs. Ingenuity is accompanied by interdependence.[5]
This brief study of the miraculous manufacturing process of photosynthesis provides a glimpse of the Creator who cares about the incredible organization and every intricate detail of plants and their role within the biosphere. Let us not miss these scientific evidences of the majesty and greatness of our awesome Creator God.
NOTES
[1] J Whitmarsh, Govindjee. The photosynthetic process. In: GS Singhal, G Renger, SK Sopory, KD Springer, editors. Concepts in photobiology: photosyn-thesis and photomorphogenesis. New York: Springer; 2013, pp. 11–51.
[2] R Muhaidat, RF Sage, NG Dengler. Diversity of Kranz anatomy and biochemistry in C4 eudicots. American Journal of Botany 2007; 94(3):362– 381.
[3] SN Pandey, BK Sinha. Photosynthesis. Plant Physiology. 4th ed. New Delhi (India): Vikas; 2005, pp. 222–239.
[4] JM Berg, L Stryer, JL Tymoczko, GJ Gatto. Biochemistry. 8th ed. New York: W. H. Freeman; 2015.
[5] EP Odum, GW Barrett. Fundamentals of ecology. 5th ed. Belmont (CA): Thomson Brooks/Cole; 2005.
Susan Thomas is dean of Sciences at Spicer Adventist University. She holds a PhD in Botany from the University of Pune, India. She has taught philosophy of science classes at both the undergraduate and graduate levels and is engaged in a number of creation-evolution discussions and presentations. She guides students in research with focus on applications in biotechnology, mycology, medicinal plants, and nanotechnology.