![]() Summary of cellular respiration essentials Metabolic pathways carry out reactions that capture energy from these various sources (organic compounds, sunlight or chemicals) and couple them to synthesis of ATP from ADP. examples include cyanobacteria and green plants.examples include purple non-sulfur bacteria, green-non-sulfur bacteria, and heliobacteria.photo: get energy from sunlight to make ATP.examples include extremophiles (extreme-loving) bacteria or archaea that live in extreme environments like deep sea thermal vents or high-salt conditions like the Dead Sea (almost 10 times as salty as the ocean).auto: make their own organic carbon compounds from carbon dioxide.chemo: get energy from chemical reactions (oxidation of inorganic compounds) to make ATP.hetero: get organic carbon from metabolism of pre-existing organic compounds.chemo: get energy from chemical reactions (oxidation of pre-existing organic compounds).We can classify organisms according to their source of energy (used to make ATP) and their source of carbon (used to make organic compounds): The energy for ATP synthesis comes from organic molecules (such as carbohydrates), or from sunlight, or from inorganic electron donors. Compare and contrast aerobic and anaerobic respiration.Explain the role of NAD+/NADH as an electron shuttle.Identify what molecule is oxidized, and what molecule is reduced in a redox reaction.Explain how proton gradients are generated across membranes.Explain how ATP synthase exploits the proton motive force to make ATP.Explain the difference between substrate-level phosphorylation and oxidative phosphorylation.Identify whether an organism is a heterotroph, photoautotroph or chemoautotroph based on their sources of energy and organic carbon.They absorb photons with high efficiency so that whenever a pigment in the photosynthetic reaction center absorbs a photon, an electron from the pigment is excited and transferred to another molecule almost instantaneously. The two photosystems performing all of this magic are protein complexes that are similar in structure and means of operation. Energy for the entire process came from four photons of light. The electrons have made their way from water to NADPH via carriers in the thylakoid membrane and their movement has released sufficient energy to make ATP. At this point, the light cycle is complete - water has been oxidized, ATP has been created, and NADPH has been made. Note that reduction of NADP+ to NADPH requires two electrons and one proton, so the four electrons and two protons from oxidation of water will result in production of two molecules of NADPH. Ferredoxin then passes the electron off to the last protein in the system known as Ferredoxin:NADP+ oxidoreductase, which gives the electron and a proton to NADP+, creating NADPH. Meanwhile, the excited electron from PS I passes through an iron-sulfur protein, which gives the electron to ferredoxin (another iron sulfur protein). PS I gains a positive charge as a result of the loss of an excited electron and pulls the electron in plastocyanin away from it. With absorption of a photon of light by PS I, a process begins, that is similar to the process in PS II. Cb6f drops the electron off at plastocyanin, which holds it until the next excitation process begins with absorption of another photon of light at 700 nm by PS I. ATP synthase makes ATP from the proton gradient created in this way. PQH2 passes these to the Cytochrome b6f complex (Cb6f) which uses passage of electrons through it to pump protons into the thylakoid space.
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