Photosynthesis Problem Set 2 - University of Arizona
Photosynthesis and respiration
Center for Bioenergy & Photosynthesis
(See Figure 1) It is commonly used as a basic building block for programmed synthetic DNA assemblies.The method outlined allows for the optimum arrangement of chromophores to be modeled, producing a light-harvesting circuit that can efficiently carry the energy of an absorbed photon over distance along the DNA architecture with minimal energy loss along the way.“The ability to model and build molecular circuits for gathering light energy and moving it around in a controlled fashion, opens the door for the design and development of a variety of nano-scale devices that are powered and controlled by light,” Woodbury said.The resulting synthetic circuit allows the absorption spectra of the chromophores to be subtly tuned in a manner similar to natural light-harvesting systems. This can be accomplished in part by precisely controlling the orientation of dye molecules and their distance from each other.Quantum LeapRecently, researchers have determined that part of the success of natural photosynthetic systems is due to quirky physical effects belonging to the quantum world.
Photosynthesis is not an immediate process. The entire chain of events will not occur as soon as the sunlight hits the leaves. Some of it will actually occur in darkness when there is no visible sunlight. Photosynthesis is split into two separate parts referred to light dependent and light independent reactions. The light dependent reaction happens when sunlight is captured and used to begin the process, resulting in the creation of a molecule known as ATP. ATP is a free energy containing molecule and is produced through a chain of steps starting when chlorophyll absorbs light energy. The light independent reaction creates glucose through the Calvin cycle, which uses the ATP and carbon dioxide to make sugar. Dark or light independent reactions occur in the stroma of the plant.
Realizing artificial photosynthesis — Arizona State …
Meanwhile, Redding and his team have just begun artificially converting the symmetric reaction center of heliobacteria into an asymmetrical one, following in the footsteps of two researchers in Japan, Hirozo Oh-Oka of Osaka University and Chihiro Azai of Ritsumeikan University, who have spent more than a decade doing this in another type of photosynthetic bacterium. The groups believe their work will clarify how these adaptations would have occurred in real life in the distant past.
Cardona, who was not involved in the recent study but has begun interpreting its results, thinks he may have found a hint in the heliobacterium reaction center. According to him, the complex seems to have structural elements that would have later lent themselves to the production of oxygen during photosynthesis, even if that wasn’t their initial purpose. He found that a particular binding site for calcium in the heliobacteria’s structure was identical to the position of the manganese cluster in photosystem II, which made it possible to oxidize water and produce oxygen.
What Is Photosynthesis? From Light Energy to Chemical …
By Martin Schweig
My first interest in succulent plants developed because of their unique physical differences to most other botanical species. What I did not realize was how different they were in many other aspects of their existence.
Their basic biochemical process is somewhat different from the chemistry of most other plants. To survive in a dry environment with irregular or little rainfall, succulent plants must store water in their leaves, stems or roots. These plants often show specific adaptations in their metabolism.
As we know, plants produce food by photosynthesis, which is the bonding together of carbon dioxide with water to make sugar and oxygen using the sun's energy. Sugar contains the stored energy and serves as the raw material from which other compounds are made.
What I was not aware of is that there are at least three different pathways in which photosynthesis can occur to achieve the same results. They are known as C3, C4 and CAM, because the first chemical made by the plant is a three- or four-chain molecule.
C3 (normal conditions)
C4 (high temperature/high water/high light availability)
CAM (high temperature/low water availability)
CAM stands for crassulacean acid metabolism, after the plant family in which it was first discovered. It is essentially a means of isolating in time the carbon dioxide intake from sunlight-fueled photosynthesis. Acid is stored at night within the plant so that during the day it can be turned into sugars by photosynthesis.
All plants can use C3 photosynthesis, and some are able to use all three types. However, C4 and CAM do not exist in the same plant. It is interesting to note that the only cacti to use C3 photosynthesis is the primitive pereskia.
C4 and CAM photosynthesis are both adaptations to arid conditions, because they are more efficient in the conservation of water. CAM plants are also able to "idle," thus saving energy and water during periods of harsh conditions. CAM plants include many succulents such as Cactaceae, Agavacea, Crassulaceae, Euphorbiaceae, Liliaceae, Vitaceae (grapes), Orchidaceae and bromeliads.
CAM plants take in carbon dioxide during the night hours, fixing it within the plant as an organic acid with the help of an enzyme. During the daylight hours, CAM plants can have normal C3 metabolism, converting carbon dioxide directly into sugars or storing it for the next day's metabolism for use in the evening.
With the sun's energy during daylight, the stored organic acid is broken down internally with the help of enzymes to release carbon dioxide within the plant to make sugars. The stomata (pores) can be open during the evening when the temperature is lower and humidity relatively higher.
During the day, the stomata can remain closed, using the internally released carbon dioxide and thus sealing the plant off from the outside environment. This is probably a six to 10 times more efficient way to prevent water loss compared to normal plant respiration. This modified effect seems to work best when there is a considerable difference between daytime and nighttime temperatures.
C4 plants can photosynthesize faster under a desert's extreme heat than C3 plants, because they use extra biochemical pathways and anatomy to reduce photorespiration. Photorespiration basically occurs when the enzyme (rubisco) that grabs carbon dioxide for photosynthesis grabs oxygen instead, causing respiration that blocks photosynthesis and thus causes a slowing of the production of sugars.
The majority of plants fall into the C3 category and are best adapted to rather cool, moist temperatures and normal light conditions. Their stomata are usually open during the day.
When conditions are extremely arid, CAM plants can just leave their stoma closed night and day, and the organic cycle is fed by internal recycling of the nocturnally fixed respiratory carbon dioxide. Of course, this is somewhat like a perpetual motion machine, and because there are costs in running this machinery, the plant cannot CAM-idle for very long. This idling does, however, allow the plants to survive dry spells and recover quickly when water is again available. This is quite unlike plants that drop their leaves and go dormant during dry spells.
The following comparison of photosynthesis and respiration may be helpful.
“Nature’s invention of photosynthesis is the single most important energy conversion process driving the biosphere, and photosynthesis forever changed the Earth’s atmosphere,” said Raimund Fromme, associate research professor at the Arizona State University (ASU) Biodesign Institute’s Center for Applied Structural Biology and in the School of Molecular Sciences.
27th Western Photosynthesis Conference
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Photosynthesis also produces energy-rich carbohydrates like starch
Photosynthesis occurs in the chloroplast of a plant cell ..
Both types of photosystem come together in green plants, algae and cyanobacteria to perform a particularly complex form of photosynthesis—oxygenic photosynthesis—that produces energy (in the form of ATP and carbohydrates) as well as oxygen, a byproduct toxic to many cells. The remaining photosynthetic organisms, all of which are bacteria, use only one type of reaction center or the other.
ASU team shines new light on photosynthesis | ASU …
The latest important clue comes from Heliobacterium modesticaldum, which has the distinction of being the simplest known photosynthetic bacterium. Its reaction center, researchers think, is the closest thing available to the original complex. Ever since the biologists , and of Arizona State University, in collaboration with their colleagues at Penn State, published in a July edition of Science, experts have been unpacking exactly what it means for the evolution of photosynthesis. “It’s really a window into the past,” Gisriel said.
Arizona State University - Tempe
their best glimpse yet into the origins of photosynthesis, one of nature’s most momentous innovations. By taking near-atomic, high-resolution X-ray images of proteins from primitive bacteria, investigators at Arizona State University and Pennsylvania State University have extrapolated what the earliest version of photosynthesis might have looked like nearly 3.5 billion years ago. If they are right, their findings could rewrite the evolutionary history of the process that life uses to convert sunlight into chemical energy.
Study 22 Photosynthesis flashcards from Jacklyn R. on StudyBlue.
In artificial photosynthesis, scientists are essentially conducting the same fundamental process that occurs in natural photosynthesis but with simpler nanostructures. The fabrication of these nanostructures has only recently been possible due to breakthroughs in nanotechnology in the areas of imaging and manipulation. With the core processes in photosynthesis being light gathering, charge separation, and recombination, the goal of scientists has been to create efficient synthetic nanostructures that can function as antennae and reaction centers. Devens Gust and fellow researchers at Arizona State University created a hexad, or six-part, nanoparticle made of four zinc tetraarylporphyrin molecules, (PZP)3-PZC, a free-base porphyrin, and a fullerene molecule, P-C60.
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