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Exam II Material - Exam II Material 1 Metabolism 1.1...

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30-nm fiber 10-nm fiber Exam II Material 1. Metabolism 1. Metabolism is the sum of all chemical activity in the cell – thousands of individual reactions 1.1. Catabolism takes molecules (Food) and breaks them down 1.1.1. Releases energy 1.1.2. Final products used at precursors for new molecules 1.2. Biosynthesis takes precursors and makes macromolecules 1.2.1. Biosynthetic reactions require energy and get it from catabolic reactions 2. How do we get the energy from our food to use in biosynthesis? 2.1. Carbon and Hydrogen in food isn’t stable, so they’re reactive. They want to be CO 2 and H 2 O. 2.2. A series of reactions breaks down large organic molecules like glucose to these molecules 2.2.1. Carbon and Hydrogen are oxidized 2.2.2. Spread out over more than 20 reactions to harness more of the energy 2.2.3. Each reaction controlled by a specific enzyme 3. Oxidation reactions involve removal of electrons 3.1. Electros are transferred to a molecule which becomes reduced 3.2. Ox idation and red uction reactions must balance 3.3. Most electrons transferred in redox rxns are in the form of 2 H atoms 3.4. Recipients of electrons in redox rxns are often special molecules associated with enzymes called cofactors or coenzymes 3.4.1. Coenzymes are temporary carriers of energy 3.4.2. 2 main coenzymes in biological oxidation (accept 2 H + ) 3.4.2.1. NAD+ -> reduced to NADH (actually accepts 2 e - and 1 H + )
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3.4.2.2. FAD -> reduced to FADH 2 3.4.3. Ultimately all the energy harnessed from the oxidation of food sources is used to make ATP (A denosine T riP hosphate) which is the most common “currency” of energy in the cell 3.4.3.1. Energy in ATP comes from the phosphate groups being unstable (negative charges repel) 3.4.3.2. Hydrolysis of ATP yields ADP, an inorganic phosphate, and energy 3.4.3.3. ATP  ADP + P i ΔG = -7 kcal/mol 4. How does ATP drive energy-requiring rxns? 4.1. ATP hydrolysis is coupled to the endergonic rxn 4.2. The reaction that requires energy uses the energy provided upon hydrolysis of ATP 4.2.1. Example: Glucose Glucose-6-Phosphate ΔG = +3 kcal/mol ATP ADP + P i ΔG = -7 kcal/mol Net result of these coupled rxns: ΔG = -4 kcal/mol 4.2.2. Coupled rxns often shown as: 5. Cellular Respiration 5.1. Gets the energy from food to ATP 5.2. Breakdown of glucose to CO 2 and H 2 O 5.3. Multiple reactions in 3 distinct pathways 5.3.1. Glycolysis 5.3.2. Pyruvate Oxidation & The Krebs (or Citric Acid) Cycle 5.3.3. Electron Transport Chain & Oxidative Phosphorylation 5.4. Glycolysis
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5.4.1. First pathway in breakdown of glucose 5.4.1.1. “glycol” (sugar) + “lysis” (splitting) 5.4.1.2. Starts with a 6-carbon sugar (glucose), ends with two 3- carbon molecules (pyruvate) 5.4.2. Pathway is actually endergonic up to production of first 3-carbon molecules (uses cell’s store of ATP) 5.4.3. OCCURS IN CYTOPLASM OF ALL LIVING CELLS 5.4.4. 5.4.4.1. 2 steps are endergonic 5.4.4.2. 3 steps are exergonic 5.4.4.3. Energy from first exergonic step in harnessed by transfer of electrons to NAD + (energy is not used to directly synthesize ATP, but is “saved” and used later)
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5.4.4.4. Energy from other exergonic rxns is in form of P, which is
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