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Photosynthesis Study Questions Flashcards | Quizlet

The growth and metabolism of the plant root system is supported by the process of photosynthesis occurring in the leaves.

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The Light-Dependent Reactions of Photosynthesis

The earliest photosynthetic organisms on land would have resembled modern algae, cyanobacteria, and lichens, followed by bryophytes (liverworts & mosses, which evolved from the group of green algae). Bryophytes are described as seedless, nonvascular plants. Their lack of tissue for transport of water and nutrients limits their size (most are between 2 and 20 cm high). Bryophytes don't have typical stems, leaves, or roots, but are anchored to the ground by rhizoids. They can grow in a wide range of environments and are : when the environment dries so does the plant, remaining dormant while dry but recovering rapidly when wetted. These features make them important pioneer species.

Photosynthesis Root Structures Root Cap: root tips are covered and protected by the root cap.

When a photosensitizer is hit with a photon it oxidizes, transfering photoexcited electrons to the hydrogen catalyst. This drives a reduction reaction whereby the water splitting catalyst strips electrons from water to fill the deficit in the photosensitzer just as in nature. Meanwhile the hydrogen catalyst receives the energized electrons from the photosensitizer and the free floating protons from the water splitting step and generates hydrogen gas (H2). The key to artificial photosynthesis lies in finding the right catalyst to drive each step of the reaction, and deciding whether hydrogen fuel is the end goal, or fixing carbon dioxide and generating useful hydrocarbons is preferred.

Photosynthesis relies on water and sunlight for ..

The overall process of the photosynthetic electron transport chain in chloroplasts is:

The sun's role Color Spectrum of Plants The leaves of plants look
green because their pigments absorb red and blue light and transmit and reflect green light
The two peak colors absorbed by
plants for photosynthesis, are around 450 nm or blue light and 670 nm or red light Adaptions of C4 Leaf Functions To compete for light for photosynthesis, i.e., the manufacture of sugars
Small openings on the leaf, known as stomata,regulate moisture and gas exchange (water and carbon dioxide) and temperature (cooling effect as water vapor escapes through stomata).
Evotranspiration: is a term describing the transport of water into the atmosphere from surfaces, including soil (soil evaporation), and from vegetation (transpiration).

The Cyanobacteria (blue-green algae) are a group of prokaryotes that are extremely important both ecologically (especially in global carbon and nitrogen cycles) and evolutionary terms. Stromatolites, which are formed by cyanobacteria, provide living and fossil evidence of cyanobacteria going back 2700 million years. Today stromatolites grow only in shallow, salty pools in hot, dry climates (e.g. Shark Bay in Western Australia), and their abundance in ancient rocks implies similar environmental conditions in those times. Stromatolites and other cyanobacteria were the main contributors to the marked increase in atmospheric oxygen concentrations that began around 2000 million years ago. Today, cyanobacteria are found everywhere - in marine, freshwater and terrestrial environments and as symbionts e.g. lichen - and contribute up to 50% of the atmosphere's oxygen.

**Both photosystems are identical chlorophyll ..

Plastoquinone, in turn, transfers electrons to b6f, which feeds them into PS I.

Light Dependent Processes In these processes light is necessary for energy to obtained and takes place in the thylakoid membrane.
When light first hits the chlorophyll it excites the electrons and they jump to a higher energy level.
Through the electron transport chain this energy is converted into ATP and NADPH, which are used to make carbon to carbon bonds for the Dark reactions.

Because prokaryotes are largely invisible to the human eye we tend to forget about them. However, they contributed to the development of an oxygen-rich atmosphere early in Earth's history, and are essential to the processes of decomposition and nutrient cycling, a key role in all ecosystems. They also made a significant contribution to the evolution of the better-known, , life forms.

Green sulfur bacteria contain a photosystem that is analogous to PS I in chloroplasts:
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  • Where are photosystems I and II found

    The leaves are reduced to spines, and the thick green, fleshy stems are where photosynthesis takes place.

  • C 8 - Photosynthesis and Respiration - DFJHS Science

    The excited electron passes to the plastoquinone which then passes it to the proton pump known as b6-f complex.

  • Plant Pigments and Photosynthesis

    Protons in the stroma are then forced through the ATP synthase which assembles ATP, known as photophosphorylation.

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Determining the relative efficiency of photosynthesis and ..

Cobalt Oxide (CoO) Nanoparticles. When it comes to hydrogen generation from the photocatalysis of water, conventional catalysts usually require additional reagents and external biases to produce stoichiometric amounts of hydrogen and oxygen gas. In 2013, researchers at the University of Houston discovered that Cobalt Oxide (CoO) nanoparticles were capable of decomposing water under visible light without the need of co-catalysts, reagents, or other additives. Current state of the art water splitting devices sport terribly low solar-to-hydrogen conversion efficiencies, on the order of 0.1% but these CoO nanoparticles achieved 5% conversion efficiency in the lab. A relatively new discovery, it will likely be some time before we see the first photochemical cells using CoO in the field, but the initial test results have the artificial photosynthesis community excited.

transfer from water to NADP+ relies on two photosystems acting in ..

CO2 Reduction Catalysts. Since photoautotrophs evolved in a reducing environment virtually all of photosynthesis in nature relies on the inefficient enzyme RuBisCO as part of the Calvin Cycle. It was unnecessary for natural selection to evolve a better catalyst because of the abundance of CO2 in the environment. RuBisCO is too slow for industrial processes, only sequestering a few molecules of CO2 per minute into ribulose-1,5-bisphosphate per minute. Researchers are instead turning to metal catalysts like transition metal polyphosphine complexes which are still in development, but aim to be able to reduce CO2 from air at atmospheric pressure at a faster rate

Electron flow between the two photosystems …

Photoelectrochemical Cells. Photoelectrochemical cells or PECs are mankind's best attempt at artificial photosynthesis. They use solar cells to power the electrolysis of water to produce hydrogen and oxygen gas. In its simplest implementation, incoming photons excite four surface electrons of a silicon electrode, which in turn flow through wires to a stainless steel electrode to where they split four water molecules into two hydrogen molecules (H2) and 4 hydroxide ions (OH-). The four OH- groups pass through the liquid electrolyte back to the surface of the silicon electrode and refill the four electron holes created when the previous four photoelectrons left the cell. This results in the production of two water molecules and two oxygen molecules. The direct conversion of sunlight into a fuel makes PECs a near mirror image of the photosynthetic process.

What are the functions of photosystems I and II and the Calvin Cycle

Dye Sensitized Solar Cells. Dye sensitized solar cells are low cost solar cells that combine a photosensitized anode with an electrolyte to create an artificial photosynthetic system. In the most common implementation, a porous layer of TiO2 nanoparticles is impregnated with a molecular dye that absorbs a targeted spectrum of light. The TiO2 layer is immersed in an electrolyte solution and forms the anode of the system. A platinum cathode is placed on the other side of the electrochemical cell completing a circuit. The oxidation reduction reaction is driven by the photoexcitation of electrons within the dye, and the semiconducting layer serves as the scaffold which supports a large number of dye molecules in a 3-D matrix increasing the amount of active material per surface area of the cell. By itself, the dye sensitized solar cell mimics the photoexcited locomotion of electrons within the thylakoid of a chloroplast. To completely mimic photosynthesis, the current produced by the cell can be used to power the electrolysis of water into hydrogen and oxygen gas. However power from a dye sensitized solar cell can just as easily be stored in a battery or integrated directly into the electrical grid, as with conventional solar cells.

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