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CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY

CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY. Section A: The Principles of Energy Harvest. مـراحـل الـتـنـفـــس. حويصلات هوائية. 1- تـنـفـس خـارجـي. الــدم. 3- تـنـفـس خـلـوي. خلايا الجـســم. 2- تـنـفـس داخـلــي. Overall process.

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CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY

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  1. CELLULAR RESPIRATION: HARVESTING CHEMICAL ENERGY Section A: The Principles of Energy Harvest

  2. مـراحـل الـتـنـفـــس حويصلات هوائية 1- تـنـفـس خـارجـي الــدم 3- تـنـفـس خـلـوي خلايا الجـســم 2- تـنـفـس داخـلــي

  3. Overall process • Organic compounds + O2 → CO2 + H2O + energy • Food is the fuel for cellular respiration. • Cellular respiration is a catabolic pathway: it releases energy by breaking down complex molecules. • Cellular respiration involves movement of electrons (gain or loss). • We will study the breakdown of glucose as an example.

  4. Section A: The Principles of Energy Harvest • Cellular respiration and fermentation التخمر are catabolic, energy-yielding مُنتِج للطاقةهدْم pathways. • Cells recycle the ATP they use for work. • Redox reactions تفاعلات الأكسدة-الإختزال release energy when electrons move closer to electronegative atoms. • Electrons “fall” تنتقل from organic molecules to oxygen during cellular respiration. • 5. The “fall” of electrons during respiration is stepwise مَرْحَلي, viaNAD+ and an Electron Transport Chain.

  5. 1. Cellular respiration and fermentation are catabolic, energy-yielding مُنتج للطاقة pathways • Organic molecules store energy in their arrangement of atoms. • Enzymes catalyze the systematic degradation of organic molecules that are rich in energy to simpler products with less energy. • Some of the released energy is used to do work and the rest is dissipated as heat. • Metabolic pathways that release the energy stored in complex organic molecules are catabolic هدْمي. • Fermentation is a type of catabolic process leads to the partial degradation التحلل الجزئي of sugars in the absence of oxygen. • Cellular respiration is a more important catabolic process, uses oxygen as a reactant to complete the breakdown of a variety of organic molecules. • This process is: • Organic compounds + O2 -> CO2 + H2O +Energy • Carbohydrates, fats, and proteins can all be used as the fuel, but we will start learning with glucose. • C6H12O6 + 6O2 -> 6CO2 + 6H2O + Energy (ATP + heat)

  6. O2 H2O + O2 CO2 Organic compounds + O2 Energy + CO2 + H2O Cellular Respiration Energy Food (Fuel of energy) Respiration Cellular Activities

  7. 2. Cells recycle the ATP they use for work • ATP (Adenosine Tri-Phosphate) is the important molecule in cellular energeticsعمليات إنتاج الطاقة. • The attachment of three negatively-charged phosphate groups (P) is an unstableغير مستقر, energy-storingمخزن للطاقةarrangement. • Loss of the end phosphate group release energy. • Thus, it can diffuse to any part of the cell and and release energy. • The price of most cellular work is the conversion of ATP to ADP and phosphate (P). • An animal cell regenerates تعيد إنتاجATP from ADP by adding Pvia the catabolism هدم of organic molecules.

  8. P P P P P Adenosine Tri-Phosphate (ATP) Adenosine + H2O Triphosphate Energy P Adenosine Di-Phosphate

  9. The transfer of the terminal phosphate group from ATP to another molecule is phosphorylationفـَسْـفـَرة. • This changes the shape of the receiving molecule in order to work (transport, mechanical, or chemical). • When the phosphate groups leaves the • molecule, the • molecule returns to • its original shape (stop).

  10. P Cell respiration P P Motor Protein How dose ATP drive cellular work ? P Microtubule Organelle P Energy

  11. Oxidation (reducing agent) Reduction (oxidizing agent) X Y X Y + + Na + Cl Na+ + Cl- 3. Redox reactions release energy when electrons move closer to electronegative atoms • Catabolic pathways relocate يبدل أماكن the electrons stored in food molecules, releasing energy that is used to synthesize لتخليق ATP. • Oxidation-reduction reactions (Redox reactions): Are reactions that result in the transfer of one or more electrons from one reactant to another • Oxidation: Is the loss فقـد of electrons. • Reduction: Is the addition إكتساب of electrons. Redox reactions require both a donor and acceptor of e. + e- Energy

  12. e- C6H12O6+6O2 6CO2 + 6H2O +(ATP + Heat) Reducing agent Oxidizing agent 4. Electrons “fall” from organic molecules to oxygen during cellular respiration • In cellular respiration, glucose and other fuel molecules are oxidized, releasing energy. • Glucose is oxidized, oxygen is reduced, and electrons loose potential energy. • H is the source of electrons that transfere to O. • Thus, molecules that have an abundance of وفرة من hydrogen are excellent fuels because their bonds are a source of electrons that “fall” closer to oxygen. • Enzymes lower the barrier of activation energy, allowing these fuels to be oxidized slowly. • When H moves to O, it leaves bonds which degenerated to release energy. • The resulting energy is used by the cell to synthesis ATP. Energy = 686 kcal/mol Energy

  13. Dehydrogenase H-C-OH + NAD+ C=O + NADH + H+ 5. The “fall” of electrons الإنحدار الإليكتروني during respiration is stepwise مرحلي, by NAD+ and an electron transport chain • Cellular respiration does not oxidize glucose in a single step that transfers all the hydrogen in glucose to oxygen at one time. • Rather, glucose and other fuels are broken down gradually تدريجيا in a series of steps, each catalyzed by a specific enzyme. • At key steps فى الخطوات الأساسية, hydrogen atoms move from glucose and passed first to the coenzyme NAD+(Nicotinamide Adenine Dinucleotide). • Dehydrogenase enzymes strip two hydrogen atoms from the fuel (e.g., glucose), pass two electrons to NAD+ and release H+. • This changes the oxidized form, NAD+, to the reduced formNADH. Thus, NAD+ is oxidizing agent as it accept electrons. • NAD+ functions as the oxidizing agent in many of the redox steps during the catabolism of glucose. As electrons “fall” from NADH to oxygen, their energy is used to synthesize ATP.

  14. Final hints • The most common carrier is NAD+ • H atoms have one proton and one electron • When two H atoms are removed from a substrate NAD+ accepts the electrons from both atoms and a proton from one of them • NAD+ + 2H→ NADH + H+

  15. The electron transport chain, consisting of several molecules (primarily proteins), is built into the inner membrane of a mitochondrion. • NADH takes electrons from food to the “top” of the chain. • At the “bottom”, oxygen captures the electrons and H+ to form water. • The free energy change from “top” to “bottom” is -53 kcal/mole of NADH. • Electrons are passed by increasingly electronegative molecules in the chain until they are caught by oxygen (the most electronegative). • Cellular respiration uses an electron transport chainسلسلة نقلالإليكترونات to break يـُقـَسم the fall of electrons to O2 into several steps عدة خطوات.

  16. Electron Fall Mitochondrion e e NAD+ FoodNADHTransport chainOxygen H ATP ADP The Cell Summary of electron “Fall” steps during respiration - Falling of all H atoms from glucose to O is gradually not at once. - It occurs in steps, each one is catalyzed by an enzyme. - H atoms of glucose pass first to the co-enzyme NAD+to form NADH - Then from NADH to electron transport chain, and finally to O and releases energy to form ATP. Energy

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