Photosynthesis
One of the characteristics that distinct plants and animals is photosynthesis, which is process that can produce glucose itself by using CO2 and sunlight. Let's see how this happens.
Light-dependent reaction
During this period, chloraplasts require light energy as we familiar with, at which oxygen and energy are produced.
First, light stimulates photosystem II (PS II), a large complex of proteins and pigments that absorbs light, and the energy is transfered to the chlorophyll called P680 at the center of PSII, boosting an electron to pass to a accepcter molecule. The hydrogen in water molecules provide electrons to replace the one in PSII, leaving oxygen atoms to form oxygen and released. Starts from PSII, the electron travels down the electron transport chain (ETC), lossing some of its energy, and the leaked energy pumps the hydrogen ions from stroma (outside) into thylakoid lamen (inside). The H+ gradient allows H+ to flow back to stroma by passing through ATP synthase and finally binds to ADP to form ATP.
At the same time, the electron continues its trip to PSI and joins the P700 chlorophyll. When light is absorbed by PSI and passed toward P700, the electron will again be boosted and pass along the second ETC to bind with H+ and NADP+ to form NADPH.
Light-independent reaction (Calvin cycle)
It is the period that the chloraplasts do not utilize light and the part that I think is the most difficult one to remember.
There are three steps:
Carbon Fixation
An enzyme nicknamed rubisco (RuBP carboxylase-oxygenase) catalyzes attachment of CO2 to a five-carbon sugar called ribulose bisphosphate (RuBP). The resulting 6-carbon molecule is unstable, however, and quickly splits into two molecules of a three-carbon compound called 3-phosphoglycerate (3-PGA). Thus, for each CO2 that enters the cycle, two 3-PGA molecules are produced.
Reduction
First, each molecule of 3-PGA receives a phosphate group from ATP, turning into a doubly phosphorylated molecule called 1,3-bisphosphoglycerate (and leaving behind ADP as a by-product).
Second, the 1,3-bisphosphoglycerate molecules are reduced (gain electrons). Each molecule receives two electrons from NADPH and loses one of its phosphate groups, turning into a three-carbon sugar called glyceraldehyde 3-phosphate (G3P). This step produces NADP+ and phosphate (Pi) as by-products.
The ATP and NADPH used in these steps are both products of the light-dependent reactions (the first stage of photosynthesis). That is, the chemical energy of ATP and the reducing power of NADPH, both of which are generated using light energy, keep the Calvin cycle running. Reciprocally, the Calvin cycle regenerates ADP and NADP+, providing the substrates needed by the light-dependent reactions.
Regeneration
Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP and involves a complex network of reactions.
In order for one G3P to exit the cycle (and go towards glucose synthesis), three CO2 molecules must enter the cycle, providing three new atoms of fixed carbon. When three CO2 molecules enter the cycle, six G3P molecules are made. One exits the cycle and is used to make glucose, while the other five must be recycled to regenerate three molecules of the RuBP acceptor.
One of the characteristics that distinct plants and animals is photosynthesis, which is process that can produce glucose itself by using CO2 and sunlight. Let's see how this happens.
Light-dependent reaction
During this period, chloraplasts require light energy as we familiar with, at which oxygen and energy are produced.
First, light stimulates photosystem II (PS II), a large complex of proteins and pigments that absorbs light, and the energy is transfered to the chlorophyll called P680 at the center of PSII, boosting an electron to pass to a accepcter molecule. The hydrogen in water molecules provide electrons to replace the one in PSII, leaving oxygen atoms to form oxygen and released. Starts from PSII, the electron travels down the electron transport chain (ETC), lossing some of its energy, and the leaked energy pumps the hydrogen ions from stroma (outside) into thylakoid lamen (inside). The H+ gradient allows H+ to flow back to stroma by passing through ATP synthase and finally binds to ADP to form ATP.
At the same time, the electron continues its trip to PSI and joins the P700 chlorophyll. When light is absorbed by PSI and passed toward P700, the electron will again be boosted and pass along the second ETC to bind with H+ and NADP+ to form NADPH.
Light-independent reaction (Calvin cycle)
It is the period that the chloraplasts do not utilize light and the part that I think is the most difficult one to remember.
There are three steps:
Carbon Fixation
An enzyme nicknamed rubisco (RuBP carboxylase-oxygenase) catalyzes attachment of CO2 to a five-carbon sugar called ribulose bisphosphate (RuBP). The resulting 6-carbon molecule is unstable, however, and quickly splits into two molecules of a three-carbon compound called 3-phosphoglycerate (3-PGA). Thus, for each CO2 that enters the cycle, two 3-PGA molecules are produced.
Reduction
First, each molecule of 3-PGA receives a phosphate group from ATP, turning into a doubly phosphorylated molecule called 1,3-bisphosphoglycerate (and leaving behind ADP as a by-product).
Second, the 1,3-bisphosphoglycerate molecules are reduced (gain electrons). Each molecule receives two electrons from NADPH and loses one of its phosphate groups, turning into a three-carbon sugar called glyceraldehyde 3-phosphate (G3P). This step produces NADP+ and phosphate (Pi) as by-products.
The ATP and NADPH used in these steps are both products of the light-dependent reactions (the first stage of photosynthesis). That is, the chemical energy of ATP and the reducing power of NADPH, both of which are generated using light energy, keep the Calvin cycle running. Reciprocally, the Calvin cycle regenerates ADP and NADP+, providing the substrates needed by the light-dependent reactions.
Regeneration
Some G3P molecules go to make glucose, while others must be recycled to regenerate the RuBP acceptor. Regeneration requires ATP and involves a complex network of reactions.
In order for one G3P to exit the cycle (and go towards glucose synthesis), three CO2 molecules must enter the cycle, providing three new atoms of fixed carbon. When three CO2 molecules enter the cycle, six G3P molecules are made. One exits the cycle and is used to make glucose, while the other five must be recycled to regenerate three molecules of the RuBP acceptor.
#上海chi k11美术馆# Caroline Walker 被看见的女性II，“家庭"系列，Walker最新系列的作品讲述了她的嫂子丽莎成为母亲之后的成长和转变，该系列通过展现丽莎的日常居家生活来展现她初为人母的责任，Walker捕捉描绘了丽莎在分娩前四周直至孩子满三个月期间所经历的变化，每一位初为人母的观者想必都能从中找到共鸣
#spaceweather天文酷图##天文酷图#
【太阳报 - 11 月 9 日 20240406185203】
Ted Adachi 于 2020 年 11 月 9 日拍摄于加拿大魁北克省蒙特利尔
【拍摄参数】
使用的相机： 不可用 不可用
曝光时间： 不可用
光圈： 不可用
ISO：不可用
拍摄日期： 不可用
【详细说明】
Solarmax 60II f/6.6 Sony a6500 ISO 800 表面 1/500 突起 1/100 表面和突出部分为5层堆叠。使用 Lynkeos Lucy-Richardson 算法和 Photoshop 进行堆叠和着色处理。
来源：Spaceweather
版权：Ted Adachi
翻译：baidu*
*：此为机器翻译且未人工审核，可能有不通顺的地方。
【相关知识】
天文学是一门研究天体和天文现象的自然科学。它使用数学、物理和化学来解释它们的起源和演化。天文学的研究对象包括：行星、卫星、恒星、星云、星系和彗星等天体，以及超新星爆炸、伽马射线暴、类星体、耀变体、脉冲星和宇宙微波背景辐射等天文现象。更通俗地说，天文学研究起源于地球大气层之外的一切事物。宇宙学是天文学的一个分支，从整体上研究宇宙。
发布时间：2024年04月06日18时56分28秒
【太阳报 - 11 月 9 日 20240406185203】
Ted Adachi 于 2020 年 11 月 9 日拍摄于加拿大魁北克省蒙特利尔
【拍摄参数】
使用的相机： 不可用 不可用
曝光时间： 不可用
光圈： 不可用
ISO：不可用
拍摄日期： 不可用
【详细说明】
Solarmax 60II f/6.6 Sony a6500 ISO 800 表面 1/500 突起 1/100 表面和突出部分为5层堆叠。使用 Lynkeos Lucy-Richardson 算法和 Photoshop 进行堆叠和着色处理。
来源：Spaceweather
版权：Ted Adachi
翻译：baidu*
*：此为机器翻译且未人工审核，可能有不通顺的地方。
【相关知识】
天文学是一门研究天体和天文现象的自然科学。它使用数学、物理和化学来解释它们的起源和演化。天文学的研究对象包括：行星、卫星、恒星、星云、星系和彗星等天体，以及超新星爆炸、伽马射线暴、类星体、耀变体、脉冲星和宇宙微波背景辐射等天文现象。更通俗地说，天文学研究起源于地球大气层之外的一切事物。宇宙学是天文学的一个分支，从整体上研究宇宙。
发布时间：2024年04月06日18时56分28秒
✋热门推荐