07- Cellular Respiration

07- Cellular Respiration - Cellular Respiration Metabolism...

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Cellular Respiration Metabolism - Metabolism: the sum of all chemical reactions in an organism - Metabolic reactions often occur in steps - Metabolic (or biochemical) pathway - Two types of metabolic reactions: - Anabolic Reactions : build up molecules - Usually consume energy (endergonic) - Catabolic Reactions: Break down molecules - Usually release energy (exergonic) Metabolism: obtaining energy - Glycolysis and cellular respiration - Simple to describe: the reverse of photosynthesis! - The biochemical pathway of breaking down simple sugars (glucose) - A series of catabolic reactions - Extract energy to make ATP - Overall reaction: - opposite of photosynthesis - C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O Glucose as fuel - Need energy to create order - How do we convert food to energy? - The catabolism of glucose is exergonic: ΔG = -686 kcal/mol - Given this, does glucose blow up in your cabinets or in your digestive tract? - Why not?? - Activation energy and controlled oxidation (controlled energy release) - Activation energy slows down release of energy Stages of glucose catabolism - Takes place in a complex set of 4 stages: - I. Glycolysis—cleaving or splitting of glucose molecule - II. Oxidation of pyruvate - III. Krebs Cycle (aka TCA, Citric Acid Cycle) - IV. Chemiosmosis/Electron Transport Chain - (Last three are called Cellular Respiration) Mechanisms of ATP synthesis - ATP synthesis is endergonic - Energy from glucose oxidation used in the synthesis of ATP - Mechanisms of ATP synthesis - 1. Substrate level phosphorylation - Uses organic P
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- 2. Oxidative phosphorylation - Uses inorganic P Adenosine triphosphate Substrate level phosphorylation - Substrate level phosphorylation - Start with an organic molecule that has a phosphate group (PO 4 ) - Transfer that phosphate directly to ADP, making ATP - Phosphate group is always attached to something - Occurs during glycolysis and Krebs cycle - Figure 7.4 - Enzyme acts as catalyst for whole reaction - Take PEP (organic molecule w/ phosphate attached to it) and transfer it to ADP - PEP = phosphoenolpyruvate - Make ATP - PEP becomes pyruvate because it loses one phosphate group - ADP w/ extra phosphate becomes ATP Oxidative phosphorylation - Second mechanism: oxidative phosphorylation - Transfer of a free (inorganic) phosphate (Pi) to ADP to make ATP - Occurs in cellular respiration (last stage) - Requires intact mitochondria - Requires electron transport chain - need to pump protons - Uses O 2 as final electron acceptor - As the electron move down the ETC, the last member has to get rid of it. It donates electron to oxygen molecule. - Oxidative phosphorylation relies on chemiosmosis - Protons in mitochondrial spaces with intact membrane
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- escaped protons drove enzyme of ATP synthase and supplied energy - Similar to photo-phosphorylation Review - Four parts to glucose catabolism - Glycolysis - Oxidation of pyruvate - Krebs cycle - ETC/Chemiosmosis - Two mechanisms of ATP synthesis - Substrate level phosphorylation - Oxidative phosphorylation Glycolysis - Takes place in cytoplasm
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07- Cellular Respiration - Cellular Respiration Metabolism...

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