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photosynthesis    音标拼音: [f,otos'ɪnθəsɪs]
n. 光合作用

光合作用

photosynthesis
n 1: synthesis of compounds with the aid of radiant energy
(especially in plants)

Photosynthesis \Pho`to*syn"the*sis\, n. (Plant Physiol.)
The process of constructive metabolism in which green plants
utilize the energy of sunlight to manufacture carbohydrates
from carbon dioxide and water in the presence of chlorophyll.
It was formerly called {assimilation}, but this is now
commonly used as in animal physiology. --
{Pho`to*syn*thet"ic}, a. -- {Pho`to*syn*thet"ic*al*ly}, adv.
[Webster 1913 Suppl.]

Note: In green plants water is absorbed by the roots and
carried to the leaves by the xylem, and carbon dioxide
is obtained from air that enters the leaves through the
stomata and diffuses to the cells containing
chlorophyll. The green pigment chlorophyll is uniquely
capable of converting the active energy of light into a
latent form that can be stored (in food) and used when
needed.
The initial process in photosynthesis is the
decomposition of water (H2O) into oxygen, which is
released, and hydrogen; direct light is required for
this process. The hydrogen and the carbon and oxygen of
carbon dioxide (CO2) are then converted into a series
of increasingly complex compounds that result finally
in a stable organic compound, glucose (C6H12O6 ), and
water. This phase of photosynthesis utilizes stored
energy and therefore can proceed in the dark. The
simplified equation used to represent this overall
process is 6CO212H2Oenergy=C6H12O66O26H2 O. In
general, the results of this process are the reverse of
those in respiration, in which carbohydrates are
oxidized to release energy, with the production of
carbon dioxide and water.
The intermediary reactions before glucose is formed
involve several enzymes, which react with the coenzyme
ATP (see adenosine triphosphate ) to produce various
molecules. Studies using radioactive carbon have
indicated that among the intermediate products are
three-carbon molecules from which acids and amino
acids, as well as glucose, are derived.
--http://www.infoplease.com/ce6/sci/A0860378.html

Note: The role of chlorophyll
Chlorophyll contains a hydrophyllic head group and a
hydrophobic tail region. A magnesium atom is held in
the center of a cyclic, conjugated double bond
porphyrin ring which is responsible for absorbing red
light. (There also is an absorption band in the blue.
Thus red and blue are absorbed and green passes
through, giving plants a characteristic green color.)
Light is absorbed by antenna chlorophyll molecules,
then transferred to the reaction center chlorophylls.
Some hundreds of antenna chlorophyll molecules transfer
energy to a reaction center, with transfer times of
about 10-10 sec from the edge of the unit to the
center.
The energy from light is used to pump H ions from the
stroma into the thylakoid space and to reduce NADP to
NADPH. Flow of H back into the stroma releases energy
which is used to phosphorylate ADP to ATP. The
chemiosmotic coupling is working here in a similar way
to the mechanism of ATP generation used in
mitochondria.
Carbon Fixation Carbon fixation is catalyzed by
ribulose bisphosphate carboxylase (RuBP carboxylase),
the world's most abundent enzyme.
The

{ Calvin cycle} combines three carbon dioxide molecules into
one molecule of three carbon glyceraldehyde 3-phosphate.
Some plants, particularly many which live in hot, dry
climates, have a mechanism for storing carbon dioxide by
combining it with a three carbon molecule to form a four
carbon molecule. This pathway is known as the C4 or
Hatch-Slack pathway.

--http://fig.cox.miami.edu/Faculty/Tom/bil255/bil255sum98/17_photo.html
[PJC] Phototaxis


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  • Photosynthesis | Definition, Formula, Process, Diagram, Reactants . . .
    Photosynthesis is the process by which green plants and certain other organisms transform light energy into chemical energy During photosynthesis in green plants, light energy is captured and used to convert water, carbon dioxide, and minerals into oxygen and energy-rich organic compounds
  • Photosynthesis - Wikipedia
    Photosynthesis plays a critical role in producing and maintaining the oxygen content of the Earth's atmosphere, and it supplies most of the biological energy necessary for complex life on Earth [2] Some organisms also perform anoxygenic photosynthesis, which does not produce oxygen
  • Photosynthesis - National Geographic Society
    Photosynthesis is the process by which plants use sunlight, water, and carbon dioxide to create oxygen and energy in the form of sugar
  • The process of photosynthesis - Student Academic Success
    During photosynthesis, plants take in carbon dioxide from the air and water from the soil Using sunlight, they transform these into glucose (a sugar) and oxygen
  • Photosynthesis Process: Steps, Equation Diagram
    Explore the photosynthesis process with detailed steps, chemical equation, and diagrams Understand how plants convert light into energy
  • What is Photosynthesis and Why is it Important?
    During photosynthesis, chlorophyll captures light energy, which is then used to split water molecules into hydrogen and oxygen The hydrogen combines with carbon dioxide (from the air) to produce glucose, while oxygen is released into the atmosphere
  • What Is Photosynthesis and How Does the Process Work?
    Photosynthesis is a fundamental biological process through which green plants, algae, and some bacteria convert light energy into chemical energy This conversion allows these organisms to produce their own food, primarily in the form of sugars, and release oxygen as a byproduct
  • Photosynthesis: What is it and how does it work?
    Photosynthesis is the process by which carbohydrate molecules are synthesised It's used by plants, algae and certain bacteria to turn sunlight, water and carbon dioxide into oxygen and energy, in the form of sugar It’s probably the most important biochemical process on the planet
  • General Biology Photosynthesis Study Guide | Key Concepts | Notes - Pearson
    Comprehensive study guide on photosynthesis in General Biology Covers autotrophs, chloroplasts, Calvin cycle, pigments, and energy conversion
  • Photosynthesis: Biological Chemistry I Study Guide |. . .
    Photosynthesis is the biochemical process by which green plants, algae, and some bacteria convert light energy, usually from the sun, into chemical energy in the form of glucose This process not only produces glucose but also generates oxygen as a byproduct, making it essential for life on Earth and crucial for the energy flow in ecosystems





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