what happens to the free energy released as electrons are passed from photosystem 2 to photosystem 1
Primary Difference – Photosystem 1 vs 2
Photosystem I (PS I) and photosystem Two (PS II) are 2 multi-subunit membrane-protein complexes involved in oxygenic photosynthesis. Chlorophyll is the pigment involved in capturing light energy. PS ane contains chlorophyll B, chlorophyll A-670, Chlorophyll A-680, chlorophyll A-695, chlorophyll A-700 and carotenoids. Chlorophyll A-700 is the active reaction center of PS one. PS two contains chlorophyll B, chlorophyll A-660, chlorophyll A-670, chlorophyll A-680, chlorophyll A-695, chlorophyll A-700, phycobilins and xanthophylls. Chlorophyll A-680 is the active reaction center of photosystem 2. The main difference between photosystem 1 and 2 is that PS I absorbs longer wavelengths of light (>680 nm) whereas PS 2 absorbs shorter wavelengths of light (<680 nm).
This article examines,
1. What is Photosystem 1
– Definition, Characteristics, Role
2. What is Photosystem two
– Definition, Characteristics, Role
3. What is the difference between Photosystem 1 and 2
What is Photosystem i
PS I is the drove of pigments of chlorophyll, arresting mostly the wavelength of light at 700 nm. The final stage of the lite reaction is catalyzed by PS I. The reaction centre of PS I consists of chlorophyll A-700. The core of the PS I is made up of psaA and psaB subunits. Core subunits of the PS I are larger than the core subunits of PS II. PS I is fabricated upwards of chlorophyll A-670, Chlorophyll A-680, chlorophyll A-695, chlorophyll A-700, chlorophyll B and carotenoids. Photons from calorie-free are captivated by accessory pigments and passed into the reaction heart. Reaction center itself is capable of arresting photons. The free energy of absorbed photons is released from the reaction middle as high energy electrons. These electrons are transferred through series of electron carriers and finally taken up by NADP+ reductase. The enzyme, NADP+ reductase produces NADPH from these electrons. A schematic diagram of a photosystem is shown in figure 1.
Effigy 1: A photosystem
1 – Sunlight, 2 – Pigments, 3 – Reaction eye, iv – loftier free energy electron catamenia, 5 – photosystem
What is Photosystem ii
PS II is the collection of pigments of chlorophyll, arresting mostly the wavelength of light at 680 nm. The first stage of the lite reaction is catalyzed by PS II. The reaction center of PS II consists of chlorophyll A-680. PS II is an integral membrane protein, which consists of a core made up of D1 and D2 subunits. PS II consists of a lot of other proteins and pigments arranged in the photosystem. The pigments are chlorophyll A-660, chlorophyll A-670, chlorophyll A-680, chlorophyll A-695, chlorophyll A-700, chlorophyll B and phycobilins and xanthophylls. PS II achieves free energy from arresting photons or associated accessory pigments in the antenna complex. High free energy electrons are generated from the energy of the absorbed photons. These electrons are passed through an electron transport chain. During the electron transport chain, PS II passes electrons to plastoquinone (PQ), which carries the electrons to cytochrome bf complex. In PS Two, photolysis of water occurs in order to replace the released electrons from PS II. For each water molecule, that is hydrolyzed, two molecules of PQH2 are formed. The overall reaction in PS Ii is shown below.
2PQ (Plastoquinone) + 2H2O → O2 + 2PQH2 (Plastoquinol)
Figure two: Photosystem 2
Difference Between Photosystem i and 2
Location
Photosystem one: Photosystem 1 is located on the outer surface of the thylakoid membrane.
Photosystem ii: Photosystem two is located on the inner surface of the thylakoid membrane.
Photocenter
Photosystem 1: The photocenter of the photosystem 1 is P700.
Photosystem 2: The photocenter of the photosystem 2 is P680.
Absorbing Wavelength
Photosystem one: Pigments absorb longer wavelengths of light (>680 nm).
Photosystem two: Pigments absorb shorter wavelengths of light (<680 nm).
Photophosphorylation
Photosystem 1: Photosystem i is involved in both cyclic and non-cyclic photophosphorylation.
Photosystem 2: photosystem 2 is only involved in cyclic photophosphorylation.
Photolysis
Photosystem one: No photolysis of h2o occurs in photosystem 1.
Photosystem 2: Photolysis of water occurs in photosystem two.
Main Function
Photosystem 1: The main function of the photosystem one is NADPH synthesis.
Photosystem ii: The main function of the photosystem 2 is ATP synthesis and hydrolysis of water.
Electron Replacement
Photosystem 1: Released loftier energy electrons are replaced by the releasing energy of photolysis.
Photosystem 2: Released loftier energy electrons are replaced by the electrons released from photosystem II.
Pigments
Photosystem one: PS ane contains chlorophyll B, chlorophyll A-670, Chlorophyll A-680, chlorophyll A-695, chlorophyll A-700 and carotenoids.
Photosystem 2: PS 2 contains chlorophyll B, chlorophyll A-660, chlorophyll A-670, chlorophyll A-680, chlorophyll A-695, chlorophyll A-700, phycobilins and xanthophylls.
Compositon of the Core
Photosystem 1: The cadre of the PS I is made upward of psaA and psaB subunits.
Photosystem 2: The cadre of the PS Two is made up of D1 and D2 subunits.
Conclusion
PS I and PS II are the two photosystems which drive the low-cal reaction of photosynthesis. The start stage of the low-cal reaction occurs in PS Two whereas the last phase of the light reaction occurs in PS I. Each of the two photosystems are fabricated up of a collection of proteins and pigments. Chlorophylls are the major pigments found in photosystems. The reaction center of PS I consists of chlorophyll A-700 and the reaction centre of PS II consists of chlorophyll A-680. Other than chlorophylls, carotenoids are also present in photosystems. The cadre of the PS I is fabricated upwards of large subunits of psaA and psaB proteins. The core of the PS 2 is made upward of insufficiently small-scale subunits of D1 and D2. H2o molecules are hydrolyzed at PS Ii in order to replace the releasing electrons of each of the two photosystems. Electrons released from PS I are used by NADP+ reductase, producing NADPH. However, the primary difference between Photosystem one and 2 is the wavelengths of sunlight, which are captivated by each of the reaction centers of photosystems.
Reference:
1. Caffarri, Stefano, Tania Tibiletti, Robert C. Jennings, and Stefano Santabarbara. "A Comparison Between Found Photosystem I and Photosystem Two Architecture and Functioning." Electric current Protein & Peptide Science. Bentham Scientific discipline Publishers, June 2014. Web. 17 Apr. 2017.
Image Courtesy:
i. "Schema-photosysteme" By –Pinpin 19:24, 24 May 2006 (UTC) – Own work, fabricated with inkscape (CC By-SA 3.0) via Eatables Wikimedia
2. "Photosystem-2 2AXT" Past Neveu,Curtis (C31004) (CC Past-SA 3.0) via Commons Wikimedia
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