Name: photosystem i and nadph formation
Uploaded: 2019-03-11T09:21:12.000Z
Duration: 1 min 27 s
Channel: JoVE

K12 Standards

Louisiana Student Standards for Science

High School

Environmental Science

Earth’s Systems

HS-ESS2-6

Photosystem I

光化学系2と同様に，光化学系1では，光子も集光複合体内の色素分子に吸収されて エネルギーを反応中心に伝え，傘下に続いて 高エネルギー電子が 一時電子受容体に渡されます。しかしこの場合は，クロロフィルA対の不足電子は，光化学系2から電子輸送鎖を通って移動する 電子によって置き換えられます。担体分子のプラストキノンから 二重タンパク質チトクローム複合体，他のタンパク質プラストシアニンへと置き換えられます。このプロセスによって放出されたエネルギーは、チトクローム複合体を介して チラコイド空間にプロトンを送り込むために使用され、化学浸透作用によってＡＴＰを生成する プロトン勾配を作り出す。一旦電子がこの反応中心を通過すると、タンパク質複合体フェレドキシンから出発し 第二の電子輸送鎖に入ります。ここから、単一の電子は他の電子と共に NADPとレダクターゼに受容され プロトンは最終的に エネルギー生成物NADPHを形成します。

<ol>
	<li>カルドナ、T.、シャオ、S.、ニクソン、PJ植物の光合成の強化:光反応。生化学のエッセイ。62(1)、85-94(2018)。</li>
</ol>

光化学系Ⅰ

<h4>概要</h4>
 
 光化学系I(PS I)は、光化学系II(PS II)と同様に、光子を捕らえ、クロロフィル分子を介して反応中心に輸送します。PS Iでは、光子がPS IIからPS Iに入ってきた電子を再びエネルギーを与えます。反応センターでは、高エネルギーの電子が電子伝達系を通って、最終的に追加の電子とプロトンと結合し、NADP+をNADPHに還元します。このように、PS IIがエネルギーを獲得してATPを生成するのと同様、PS Iもエネルギーを獲得してNADPHを生成します。
 
 <h4>光化学系I</h4>
 
 光化学系Iの光収穫複合体の色素は光子を吸収し、そのエネルギーを反応中心(P700)に伝えます。酸化に続いて、高エネルギーの電子が、特殊なペアのクロロフィルaから一次電子受容体に渡されます。しかし今回は、クロロフィルaのペアから失われた電子は、光化学系IIから送られてきた電子と置き換えられます（PS IIのように水を分解するのではなく）。PS IIからPS Iへと移動する道中、電子は、キャリアー分子のプラストキノン、二重タンパク質のシトクロム複合体、プラストシアニンからなる電子伝達系を通過します。
 
 PS Iの反応中心で励起された電子は、フェレドキシンというタンパク質複合体からなる第2の電子伝達系に入ります。そして単体の電子は、もう1つの電子とプロトン（H+）と結合して、NADP+リダクターゼに受け取られ、NADPHが生成されます。このように、PS IIはエネルギーを獲得してプロトン勾配を作り、これが最終的にATPを作るのに使われ、PSIで獲得したエネルギーはNADPHの生成に使われます。

構造的には光化学系II(PSII)に似ていますが、光化学系I(PSI)は電子供給者と電子受容体が異なります。
これら両方...

Education

JoVE Core

Biology

生物学

Cellular Processes

細胞プロセス

Photosynthesis

光合成

KEY TERMS AND CONCEPTS

主要用語と概念

photosystem i and nadph formation

Photosystem I helps convert light energy into NADPH during photosynthesis. It works with photosystem II in the thylakoid membrane of the chloroplast, but it uses a different electron supplier and a different electron acceptor.

Electrons excited in photosystem II move to photosystem I through an electron transport chain. That chain includes plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As the electrons travel between the two photosystems, they lose energy and must be re-energized by photosystem I.

To do this, the pigments in the photosystem I antenna complex absorb another photon. The energy is passed to the reaction center called P700. P700 then sends a high-energy electron to NADP+ and forms NADPH.

Photosystem II uses light energy to build a proton gradient and make ATP. Photosystem I captures light energy to reduce NADP+ into NADPH. After ATP and NADPH are made, the cell has the energy it needs to build carbohydrate molecules for long-term storage in the stroma of the chloroplast.

Photosystem I and NADPH Formation

what is photosynthesis?

Photosynthesis in Chloroplasts and Leaves

Photosynthesis happens in plants and in some bacteria. It is the process that captures carbon dioxide and solar energy to make glucose. Glucose stores chemical energy as carbohydrates. The overall biochemical equation is 6 CO2 + 6 H2O + light energy → C6H12O6 + 6 O2. Photosynthesis also releases oxygen into the atmosphere and helps maintain Earth’s atmospheric oxygen content. Photosynthetic reactions take place in chloroplasts, which are specialized membrane-enclosed parts of the plant cell.

light as energy

How Plant Pigments Capture Light

Photosynthesis uses light energy from the sun, which is a form of electromagnetic radiation. The full range of possible wavelengths is called the electromagnetic spectrum. Light is made of photons, which are small packets of energy. Photons act like waves and are described by frequency, wavelength, and amplitude. Waves with higher frequencies carry more energy and have shorter wavelengths. Waves with lower frequencies carry less energy and have longer wavelengths. For most organisms,...

anatomy of chloroplasts

Chloroplasts and Photosynthesis in Plant Cells

Chloroplasts are the organelles where photosynthesis takes place in green algae and plants. They are also found in green stems and unripe fruit. In plants, mesophyll cells in the leaf contain the highest density of chloroplasts. Each chloroplast has a double membrane. The outer membrane faces the plant cell cytoplasm on one side and the chloroplast intermembrane space on the other. The inner membrane separates that narrow space from the stroma, which is the watery interior of the chloroplast.

photosystem ii

Photosystem II and Water Splitting

Photosystem II is a multi-protein complex that captures light energy and begins the flow of electrons in photosynthesis. It uses bound pigments to harvest photons and send that energy to its reaction center. From there, the energy continues through the electron transport chain and on to photosystem I. The pigments in photosystem II include chlorophyll a, chlorophyll b, and carotenoids. They are arranged in two parts of the photosystem: the antenna complex and the reaction center. The antenna...

photosystem i

Photosystem I helps convert light energy into NADPH during photosynthesis. It works with photosystem II in the thylakoid membrane of the chloroplast, but it uses a different electron supplier and a different electron acceptor. Electrons excited in photosystem II move to photosystem I through an electron transport chain. That chain includes plastoquinone, the dual-protein cytochrome complex, and plastocyanin. As the electrons travel between the two photosystems, they lose energy and must be...

the calvin cycle

Carbon Fixation in Photosynthesis

Photosynthesis uses light energy to turn carbon dioxide into carbohydrates. It also releases oxygen as a by-product. These products help support most food webs and make aerobic life possible. Photosynthesis has two main stages, and they happen in different parts of the chloroplast. The light-dependent reactions take place in the thylakoid membranes. Chlorophyll absorbs light energy there and helps split water molecules. This releases O2 and makes ATP and NADPH. The light-independent reactions...

c4 pathway and cam

Plant Carbon Fixation in Hot Climates

Plant carbon fixation in hot climates can follow the C4 pathway or the CAM pathway. These alternative pathways help some plants reduce energy loss from photorespiration. Photorespiration happens when oxygen levels are high and rubisco, the enzyme in the Calvin cycle, binds O2 instead of CO2. When that happens, photosynthesis slows and energy is used up. The C4 pathway is used by plants such as corn and sugarcane. In mesophyll cells, CO2 first joins with PEP, or phosphoenolpyruvate, through the...

key terms and concepts

Learn how photosystem I re-energizes electrons, reduces NADP+ to NADPH, and works with photosystem II to help build sugars in chloroplasts.

Photosystem I and NADPH Formation | JoVE K12

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JoVE Core シリーズは、生物学の重要な概念を説明する 300 を超える簡潔でわかりやすいアニメーション ビデオ レッスンに加え、今日の研究室で行われる実際の研究実験を示す 150 以上の科学者の活動ビデオを通じて、生物学に命を吹き込みます。

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Photosystem I and NADPH Formation

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