Introduction
The primary source of energy for all living things on the earth is the sun. The energy received from the sun travels 150 million kilometers to reach the earth. Although this energy comes in two forms: light and heat, the heat energy cannot be captured directly by the plants or animals. However, the heat energy does warm up the non-living surroundings of plants and animals. Only plants can capture light energy directly through the process of photosynthesis, in which plants convert the light energy into stored energy. The green plants can manufacture their own food and so plants are called as autotrophs or self-nourishing living beings. Photosynthesis is possible because green plants contain an energy- capturing substance called chlorophyll.
Analysis
Plant cells contain an organelle called the chloroplast. The chloroplast allows plants to harvest energy from sunlight. Specialized pigments in the chloroplast (including the common green pigment chlorophyll) absorb sunlight and use this energy to complete the chemical reaction:
6 CO2 + 6 H2O + energy (from sunlight) C6H12O6 (glucose) + 6 O2
The glucose that is produced is the food of the plants that is used to make other compounds. Similarly, glucose is also stacked in the plant body for further use and chemical manipulation. This glucose also forms the food for the herbivores. [Vermaas, 2004]
The whole process of photosynthesis may be divided into two stages: the light reaction and the dark reaction. The light reaction requires light while the dark reaction can occur without light. In the light reaction, electron and proton transfers occur in the presence of light and in the dark reaction, the biosynthesis of organic compounds from carbon dioxide occurs. In order to capture the light particles, the leaves of the plant have pigments called chlorophyll and various electron capturing proteins that can effectively help in the reactions that involve electron and proton exchange reactions. The excited electrons that are captured, provide the energy for the reaction centers to carry on with other chemical reactions [Whitmarch and Govindjee, 2004]
The light reaction is essentially an electron transfer reaction where excited electrons (the energy for exciting the electrons comes from the sunlight and involves various photosynthetic systems called Photosystem I and Photosystem II) are used to carry out reduction and oxidation reactions to give rise to new compounds that are further used in other reactions. For example, the electrons from water are used to reduce NADP+ to NADPH. When light strikes the Photosystem II pigments, electrons are bumped off from the porphyrin ring of chlorophyll, which ultimately reaches the Photosystem I sites. The movement of the electrons through what is called as an electron transport chain creates a lot of chemical reactions that involve transfer of electrons between compounds. Finally the electrons are used to create NADPH.
The energy that is stored in NADPH is used to reduce carbon. Similarly the light reactions also give rise to large number of ATP molecules which are formed by attaching a phosphate group to ADP. ATP is also called as the “energy currency” of the cell since it releases a large amount of energy when needed.
This step can be summarized as
H2O + light ? ½ O2 + 2H+ + 2e
2NADP+ + 2H+ + 2e- ? 2NADPH
The electrons in this reaction are also used to repair the porphyrin ring that lost electrons in the process. Hence it may be seen that the whole process involves the reuse of electrons whose movements across electron transfer systems initiates various steps in the photosynthetic cycle.
In the dark cycle the energy that is stored in NADPH and ATP is used for creating organic compounds. The dark reactions begin when the Carbon from Co2 is attached to a 5-carbon sugar compound called Ribulose bi-phosphate. After carboxylaion, the compound is broken into two molecules of 3-phosphoglycerate. The 3-phosphoglcerate is later converted to 3-phosphoglyceraldehyde. This reaction needs much energy and the energy is provided by the ATP that may be broken down in the process. The whole cycle in which the Co2 is converted to glucose was worked out by Calvin and hence is called the Calvin cycle. This cycle generates glucose as well as Ribulose bi phosphate that are circulated back into the system to aid in the photosynthetic process.
The Calvin cycle may be summarized as follows
(RuBP) + carbon dioxide ? 3-phosphorogycerate (catalysed by Rubisco)
3 C5H8P2O11 + 3 CO2 ? 6 C3H3P1O6 + H2O
3-phosphoroglycerate + ATP ? 1,3 bisphosphoroglycerate + ADP
6 C3H3P1O6 + 6 ATP ? 6 C3H3P2O10 + 6 ADP
1,3 bisphosphoroglycerate + NADPH ? 3-phosphoglyceraldehyde+ NADP+ + Pi
6 C3H3P2O10 + 6 NADPH ? 6 C3H5P1O6 + 6 NADP+ + 6 Pi
3-phosphoglyceraldehyde ? ribulose 5-phosphate + Pi
5 C3H5P1O6 ? 3 C5H8P1O7 + 2 Pi
ribulose 6-phosphate + ACP? ribulose 1,5 bisphosphate + ADP
3 C5H8P1O7 + 3 ATP ? 3 C5H8P2O11 + 3 ADP
[Wikipedia, 2004]
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Photosynthesis is a biochemical process in which plant, algae, and some bacteria harness the energy of light to produce food. Nearly all living things depend on energy produced from photosynthesis for their nourishment, making it vital to life on Earth. It is also responsible for producing the oxygen that makes up a large portion of the Earth¡¦s atmosphere. Factors that affect photosynthesis are light intensity and wave length, carbon dioxide concentration, and temperature.
Plants are autotrophs that mean they are able to synthesize food directly from inorganic compounds, instead of relying on other organisms. They use carbon dioxide gas and water to produce sugars and oxygen gas. The energy for these processes comes from photosynthesis. The equation for photosynthesis is:
Carbon dioxide+water+light„³sugar+oxygen+water.
6CO +12H O+light„³C H O+6O +6H O
The glucose is used to form other organic compounds, such as cellulose, or it may be used as fuel. This takes place through respiration found in both animals and plants. Respiration is the opposite of photosynthesis. Both respiration and photosynthesis take place through a complex sequence of steps, and are very different in detail.
Plants capture light using the pigment chlorophyll, which gives them the green colour. This is contained in organelles called chloroplasts. Although all green plants have chloroplasts, most of the energy…
No3 the metabolic processes of cellular respiration and photosynthesis recycle oxygen, as it is a reactant in respiration and a product in photosynthesis. Oxygen is released to the atmosphere by autotrophs during photosynthesis and taken up by both autotrophs and heterotrophs during respiration. It is a reactant in cellular respiration and used as the last receptor in the Electron Transport Chain, where the NADH drops off hydrogen ions, finally to the oxygen. The oxygen and hydrogen become water, which is a reactant in photosynthesis. This water is oxidized into oxygen during the light reactions carried out in photosynthesis. The light reactions use light to split apart water, a process called photolysis, which produces oxygen, hydrogen and electrons. This continual cycle of using up oxygen and then creating it again is what recycles it and helps to maintain stability in the processes and in the environment.
The rate of photosynthesis varies greatly with changes in environmental temperature in plants.
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To determine the effect of temperature on the rate of photosynthesis in plants, you would first need to formulate a hypothesis. For instance, that the rate of photosynthesis would be highest at moderate temperatures and lowest at very hot temperatures. Next, one would need to gather the materials necessary to complete the experiment. The independent variable for the experiment would be the varying temperatures one would expose the test plants to; a moderate environment where plants such as tomatoes, beans and peas would grow, a hotter environment such as in the Midwest where corn grows, and in severe heat conditions such as in the desert where cactus resides. For this specific experiment to measure the rate of photosynthesis, six of the same type, size, and age of plant would be exposed to each varying environmental temperature (two plants at each temperature) for a set period of time such as one month, and the rate of photosynthesis would be calculated, as the researcher would observe the plants daily, and make certain that other elements such as light, nutrients and water to be kept constant with the three plants, as well as the time of year and time of day that their results are recorded. After recording and comparing the data of each plant, one would formulate a conclusion based off of the results to determine the environment most favorable to a high rate of photosynthesis.
After conducting this photosynthesis experiment, one would expect the results to prove that plants perform photosynthesis at a higher rate at a moderate environmental temperature, and lower as the temperature rises and the climate differs. The two plants exposed to the moderate temperatures would perform photosynthesis at the highest rate, followed by the two plants at the hotter temperature, and lastly with the two plants at the desert-like heat conditions to perform photosynthesis at the lowest rate. The type of plants that live in moderate temperatures are able to keep their stomates open almost all day allowing for an abundance of CO2 to enter. The hotter the temperature becomes, the greater the potential to lose a lot of water, the reason why plants in hotter temperatures such as in the Midwest have to keep their stomates open less often and must concentrate CO2 in their leaves to avoid photorespiration, which is when the enzyme rubisco can bind to oxygen or CO2 if the CO2 levels are low and the oxygen levels are higher, than the rubisco binds to oxygen instead of CO2 in the dark reactions of photosynthesis. In the extremely hot temperatures such as in the desert, the rate of photosynthesis would be lower than the other two temperatures because the plants’ stomates are only open at night and are not able to take in the necessary COx to enter the plant to conduct photosynthesis and for the oxygen to leave the plant after photosynthesis. Thus, the longer the stomate can be open, the higher the rate of photosynthesis because more gases are allowed in and out of the stomate, and after the environmental temperature begins to get too high, the stomate cannot be open for as long, and cannot take in as much COx as in more moderate temperatures
No4 Abstract
Several emerging technologies are aiming to meet renewable fuel standards, mitigate greenhouse gas emissions, and provide viable alternatives to fossil fuels. Direct conversion of solar energy into fungible liquid fuel is a particularly attractive option, though conversion of that energy on an industrial scale depends on the efficiency of its capture and conversion. Large-scale programs have been undertaken in the recent past that used solar energy to grow innately oil-producing algae for biomass processing to biodiesel fuel. These efforts were ultimately deemed to be uneconomical because the costs of culturing, harvesting, and processing of algal biomass were not balanced by the process efficiencies for solar photon capture and conversion. This analysis addresses solar capture and conversion efficiencies and introduces a unique systems approach, enabled by advances in strain engineering, photobioreactor design, and a process that contradicts prejudicial opinions about the viability of industrial photosynthesis. We calculate efficiencies for this direct, continuous solar process based on common boundary conditions, empirical measurements and validated assumptions wherein genetically engineered cyanobacteria convert industrially sourced, high-concentration CO2 into secreted, fungible hydrocarbon products in a continuous process. These innovations are projected to operate at areal productivities far exceeding those based on accumulation and refining of plant or algal biomass or on prior assumptions of photosynthetic productivity. This concept, currently enabled for production of ethanol and alkane diesel fuel molecules, and operating at pilot scale, establishes a new paradigm for high productivity manufacturing of nonfossil-derived fuels and chemicals.
No5Photosynthesis – An Apercu Free Essay, Term Paper and Book Report
Cellular respiration and photosynthesis are two different, complex processes that are fundamental to the regulation of life on Earth. Cellular respiration is the series of metabolic reactions in a cell that oxidize organic molecules such as glucose to produce energy that makes ATP (Adenosine Triphosphate), carbon dioxide, and water. Conversely, cellular respiration is the process by which plants harness energy in the form of light from the sun to convert water and carbon dioxide into organic molecules and oxygen. These two processes, though direct opposites of each other, share striking similarities. For example, both processes produce ATP (the “energy currency” of the cell), and both depend on a single organelle to carry out major reactions that make cellular respiration and photosynthesis possible. The mitochondrion and the chloroplast are the organelles that house several of the reactions that occur to complete the processes of cellular respiration and photosynthesis. The mitochondrion functions as the cell’s power plant, supplying the energy necessary to carry out the many di……
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No6Photosynthesis is a process through which organisms like plants, algae, and cyanobacteria are capable of absorbing energy from sunlight and using it to produce sugar and other organic compounds such as lipids and oxygen. These photosynthetic organisms called autotrophs that are able to sustain themselves and other living things on Earth.
Solar energy is converted to chemical energy stored in the form of glucose (C6H12O6) that is then converted into ATP. In plants, this process occurs mainly within the leaves. Sunlight is absorbed by green pigments called chlorophyll. Carbon dioxide (CO2) and oxygen (O2) are exchanged with the atmosphere through tiny openings called stomata. The water (H2O) needed is absorbed from the roots and delivered to the leaves. Chloroplasts are found in the stroma and grana, where two stages of photosynthesis happen. These stages are the light dependent reactions and the light independent reactions (Calvin Cycle).
Light dependent reactions required the presence of light
and occur in the thylakoid membranes of a chloroplast. It contains two photosystems, two electron transport chains, and ATP synthase. Chlorophyll absorbs light energy that excites electrons to a higher energy level. Energized electrons from photosystem I are passed down an electron transport chain and added to NADP+ to form NADPH. Electrons from photosystem II are passed down another electron chain. Their energy is used to pump hydrogen ions (H+) from the stroma into the thylakoid compartment, creating a concentration gradient. Electrons leaving this electron transport chain enter photosystem I. Photosystem II replaces its electrons by splitting water. Hydrogen ions and oxygen are released into the thylakoid compartment, where the oxygen gas comes from. The hydrogen ion buildup inside the thylakoid compartment creates kinetic energy that allows an enzyme called ATP synthase produces ATP from ADP through the method of chemiosmosis.
