Works Cited



L M DAMASES219144761ASSIGNMEMT 2: PHOTOSYNTHESISPhotosynthesisPhotosynthesis is not only important for plants but it is essential to all life on earth as both plans and animals depend on it. According to OpenStax(2019)?photosynthesis is the only biological process that can capture energy that derives from outer space (sunlight) and can convert it into chemical compounds (carbohydrates) that every organism uses to fuel its metabolism. In short, photosynthesis is the process in which light energy is converted into chemical energy in the form of sugars CITATION Kha20 \l 1033 (Academy, 2020).The leaf as a photosynthesis machineA leaf is referred to as the organ that forms the main lateral appendage on the stem of vascular plants. In general, leaves are thin, flattened organs which are responsible for the process of photosynthesis in plants CITATION Bio17 \l 1033 (Editors, 2017). As one of the most essential parts of a plant, leaves have several important functions with its most important or primary function being the conversion of carbon dioxide, water and sunlight into glucose by the process of photosynthesis.How does the leaf act as a photosynthesis machine? Firstly, the leaf receives their characteristic green color from a pigment known as Chlorophyll, not only does it give the plant or leaf the green color but it also absorbs light energy. If one had to carefully examine the section of a leaf tissue, you would notice that the chlorophyll does not lie freely in the cell but they are confined in organelles known as chloroplasts. Chloroplasts are mostly found lying freely in the cells of the mesophyll, which is a layer with many air spaces and a very high concentration of water vapour and each mesophyll contains about 20-100 chloroplasts. Chloroplasts play the essential role of absorbing sunlight and, in conjunction with certain enzyme, use the radiant energy in decomposing water into its elements, hydrogen and oxygen CITATION TEB04 \l 1033 (Britannica, 2004). The oxygen liberated from green leaves replaces the oxygen removed from the atmosphere by plant and animal respiration and by combustion. The hydrogen obtained from water is combined with carbon dioxide in the enzymatic processes of photosynthesis to form the sugars that are the basis of both plant and animal life CITATION TEB04 \l 1033 (Britannica, 2004). Plants also consists of microscopic pores known as stomata which help in the exchange of gases from the exterior to the interior and vice versa.Dark and light reactionsThe?light-dependent reactions?use light energy to make two molecules needed for the next stage of photosynthesis: the energy storage molecule ATP and the reduced electron carrier NADPH. In plants, the light reactions take place in the thylakoid membranes of organelles called chloroplasts CITATION Kha20 \l 1033 (Academy, 2020).There are two types of photosynthetic units involved in the light phase of photosynthesis. Photosystem I and Photosystem II. One can distinguish their reaction centers as they are associated with proteins which in a way may cause a slight shift in their absorption spectrum. ”In contrast, the reaction center of Photosystem I consist of a pair of chlorophyll a molecules with an absorption peak of 700nm and is referred to as P700. The reaction center of Photosystem II is made up of a pair of chlorophyll a molecules with an absorption peak of about 680 nm and is referred to as P680” CITATION Sol10 \l 1033 (Solomon E, 2010). The process of resonance then takes place when a pigment molecule absorbs light energy, where it is passed down directly from one pigment molecule to another within the antenna complex until it reaches the reaction center. Once the energy reaches a molecule of P700 or P680, the electron is then raised to a higher energy level CITATION Sol10 \l 1033 (Solomon E, 2010).The dark reactions are responsible for the conversion of carbon dioxide to glucose. This reaction involves the combining of carbon dioxide with the five-carbon sugar ribulose 1,5-bisphosphate (RuBP) in a series of reactions called the Calvin-Benson cycle. It yields an unstable six-carbon intermediate, which immediately breaks down into two molecules of phosphoglycerate (PGA), which is a three-carbon acid CITATION Han20 \l 1033 (Lambers, 2020). Each reaction is catalyzed by a specific enzyme. Six revolutions of the cycle means that 6 carbon dioxide molecules react with 6 RuBP molecules to produce 12 molecules of PGA; 2 three-carbon PGA molecules combine to form the six-carbon glucose, and 10 PGAs are recycled to regenerate 6 molecules of RuBP. The ATP and NADPH from light reactions provide the energy and reducing power to form glucose and refurbish the CO2 acceptor, RuBP CITATION Han20 \l 1033 (Lambers, 2020),How does photosynthesis convert light energy into chemical energy?As the process of photosynthesis involved a number of steps and reactions that uses solar energy, water as well as carbon dioxide to produce organic compounds and oxygen. We learned that there are two types of reactions, which are the light and dark reactions. In the light reactions, solar energy or light energy is converted into chemical energy in the form of two energy-transporting molecules, which are ATP and NADPH. “When solar energy reaches plant cells and excites special chlorophyll molecules, they release a high-energy electron (check out the related strategy here). The release of this electron sets off a chain of electron-trading and energy-transferring events between several intermediary molecules, and the last molecule to form and hold the electrons in this chain is NADPH” CITATION Ann18 \l 1033 (Guerrero, 2018). The replacement of these excited chlorophyll molecules need to take place as these electrons come from water. With the help of enzymes and solar energy, the water is then split into electrons, protons (H+), and oxygen. The electrons go to the chlorophyll, and while the protons contribute to a proton gradient that is used to fuel the synthesis of a second energy-carrying molecule, ATP. The oxygen is a byproduct of the whole process CITATION Ann18 \l 1033 (Guerrero, 2018). The chemical energy in NADPH and ATP is then used to power steps in the subsequent carbon-fixation reactions.How does photosynthesis interact with other pathways?As discussed earlier photosynthesis is a two-part process. Where one reaction occurs in the presence of light, which is known as the light reactions, and the other one in the absence of light, which is known as the dark reactions. Carbon dioxide, water, light and minerals are processed through the various reactions to produce carbohydrates and oxygen. Carbohydrates are the energy-containing molecules that humans and animals ingest to power their own metabolic pathways. Oxygen, a waste product to plants, is necessary for respiration in mammals CITATION Joh19 \l 1033 (Newton, 2019). The reaction equation for photosynthesis goes as follows:6CO2 + 6H20 + (energy) → C6H12O6 + 6O2 Carbon dioxide + water + energy from light produces glucose and oxygen CITATION Joh19 \l 1033 (Newton, 2019)The resulting glucose is then converted to adenosine triphosphate (ATP) through cellular respiration, in order to provide energy. In addition to glucose, this reaction produces oxygen that is released by the plants into the atmosphere. CITATION Joh19 \l 1033 (Newton, 2019)The energy which was collected in the chloroplasts is then used during cellular respiration. During this process of cellular respiration, the energy which was produced from the glucose made during photosynthesis is used to produce energy molecules for growth and reproduction. The products made during respiration are energy molecules, carbon dioxide and water. The carbon dioxide and water produced are transferred back to the chloroplast where they are again used for photosynthesis. Cellular respiration takes place in another organelle called the mitochondria. Here, the energy obtained from the glucose produced in the chloroplast is created and stored for future use by the plant CITATION Joh19 \l 1033 (Newton, 2019).The chemical equation of cellular respiration:C6H12O6 + 6O2 --> 6CO2 + 6H2O + 36 or 38 ATP molecules CITATION Chr19 \l 1033 (Deziel, 2019).Photosynthesis and Cellular respiration work hand in hand as they play an important role in plants. During the process of photosynthesis, plants produce the substance that they require for survival and store it until they need it. During cellular respiration, plants carry out chemical reactions which they can derive energy from the products of photosynthesis. CITATION Edr17 \l 1033 (Koening, 2017)The Calvin CycleThe Calvin cycle is a set of light independent reactions which occur during photosynthesis. This is the process in which plants and other autotrophs mainly use to create nutrients from sunlight and carbon dioxide. These reactions occur in the stroma of the chloroplast, the stroma is the fluid-filled region between the thylakoid membrane and the inner membrane of the organelle. The Calvin cycle reactions are organized or have three stages: fixation, reduction and regeneration.Carbon Fixation: The enzyme RuBisCO catalyzes a reaction between carbon dioxide and RuBP, the carbon dioxide is reacted to produce glyceraldehyde 3-phosphate (G3P). This enzyme RuBisCo then catalyzes the carboxylation of a 5-carbon compound to make a 6-carbon compound that splits in half to form two 3-phosphoglycerate (3-PGA) molecules. The enzyme phosphoglycerate kinase catalyzes phosphorylation of 3-PGA to form 1,3-biphosphoglycerate (1,3BPGA) CITATION Ann19 \l 1033 (Helmenstine, 2019).Reduction Reaction: The enzyme glyceraldehyde 3-phosphate dehydrogenase catalyzes the reduction of 1,3BPGA by NADPH CITATION Ann19 \l 1033 (Helmenstine, 2019).Regeneration: At the end of the regeneration, the net gain of the set of reactions is one G3P molecule per 3 carbon dioxide molecules.References:Works Cited BIBLIOGRAPHY Academy, K. (2020). Intro to photosynthesis. Retrieved from Khan Academy: , T. E. (2004, April 15). Leaf (Plant) Anatomy. Retrieved from Enclopydia Britannica: , C. (2019, April 23). What is the formula for cellular respiration? Retrieved from Sciencing: , B. (2017, August 19). Biology Dictionary. Retrieved from , A. (2018, February 13). Photosynthesis converts solar energy into chemical energy. Retrieved from AskNature Team: , A. M. (2019, May 26). Calvin cycle steps and diagram. Retrieved from ThoughtCo.: , E. (2017, July 21). What is the formular for cellular respiration? Retrieved from Sciencing: , H. (2020, February 03). Plant. Retrieved from Encyclopaedia Britanicca: , J. (2019, November 22). What is the photosynthesis equation. Retrieved from Sciencing: . (2019, May 08). Overview of photosynthesis. Retrieved from CNX legacy : E, B. L. (2010). Biology (9th Ed). Brooks Cole-Thompson. ................
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