Biologych7

Biologych7 - 7.1 Overview of Energy-Releasing Pathways...

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1. Overview of Energy-Releasing Pathways Anaerobic Reactions → do not use free oxygen - m any prokaryotes and protists live in places where oxygen is absent; m ake ATP by ferm enta and other ana erobic pathways - m any eukaryotic cells still use fermentation, including skeletal m uscle cells - begins and ends in cytoplasm - net yield of (2) ATP Aerobic Respiration → oxygen-dependent pathway; most species extract energy from glucos - Begins in cytoplasm and ends in mitochondrion where oxygen accepts and removes electro drove rxns - Most ATP for e ach glucose, typically ≥ 3 6 C 6 H 12 O 6 + 6O 2 → 6CO 2 + 6H 2 O In all cells, all of main energy-releasing pathways start with same rxns in cytoplasm - Glycolysis → initial rxns during which enzym es cleave/rearrange glucose into (2) pyruvate m olecules →organic compound with 3-C backbone - After glycolysis, en ergy-releasing pathways differ Enzym es catalyze steps and interm ediates in one step are substrates for next enzym e in pa Coenzym es NAD + (nicotinamide adenine dinucleotide) and FAD (flavin adenine dinucleotide) accept electrons and hydrogen derived from intermediates of glucose breakdown - When carrying e-or H+, they are reduced to NADH and FADH 2 2. The First Stage: Glycolysis Process by which bond energy of glucose converted to bond energy of ATP (transportable form) Occurs in cytoplasm of all prokaryotic and eukaryotic cells 1. (1) 6-C sugar partly broken down to (2) 3-C pyruvate molecules 2. Initial steps are energy-requiring (investment of 2 ATP) - delivered by ATP which activates glucose by transferring P-group to it - second ATP transfers P-group to interm ediate that forms 3. Second interm ediate split into one PGAL (phosphorglyceraldehyde) and slightly different
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Biologych7 - 7.1 Overview of Energy-Releasing Pathways...

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