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Lec 18 Cellular Respiration.docx

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BIOL 1010
Igor Kovalchuk

Cellular Respiration Respiration - A cumulative function of three metabolic stages: 1. Glycolysis 2. The Krebs cycle 3. The electron transport chain and oxidative phosphorylation - Glycolysis is a catabolic pathway that: o Occurs in the cytosol o Partially oxidizes glucose o (6C) in two private o (3C) molecules - The Krebs Cycle is a catabolic pathway that: o Occurs in the mitochondrial matrix o Completes glucose oxidation by breaking down pyruvate derivative (acetyl CoA) into carbon dioxide - Glycolysis and the Krebs cycle produce: o A small amount of ATP by substrate-level phosphorylation o NADH by transferring electrons from substrate to NAD+ (Krebs cycle also produces FADH2 by transferring electrons to FAD+ - The electron transport chain stages: o Is located at the inner membrane of the mitochondrion o Accepts energized electrons from reduced coenzymes (NADH and FADH2) that are harvested during glycolysis and Krebs cycle o Couples this exergonic slide of electrons to ATP synthesis or oxidative phosphorylation. This process produces most (90%) of the ATP. Glycol sis - During glycols is each glucose molecules is broken down into two molecule of the compound private - The pryuvate crosses the double membrane of the mitochondrion to enter the matrix, where the Krebs cycle decomposes it to carbon dioxide Respiration - The electron transport chain converts the chemical energy to a form that can be used to drive oxidative phosphorylation, which accounts for most of the ATP generated by cellular respiration. - A smaller amount of ATP is formed directly during glycolysis and the Krebs cycle by substrate level phosphorylation Substrate level phosphorylation - Some ATP is made by direct enzymatic transfer of P group from a substrate to ADP - Phosphoenolpyruvate (PEP) is formed from breakdown of sugar during glycolysis Glycolysis - Harvest chemical energy by oxidizing glucose to private - Glycolysis – catabolic pathway during which six-carbon glucose is split into two three-carbon sugars, which are then oxidized and rearranged by a step-wise process that produces two private molecules o Each reaction is catalyzed by specific enzymes dissolved in the cytosol o No CO i2 released as glucose is oxidized to private; all carbon in glucose can be accounted for in the two molecules of private - Occurs whether or not oxygen is present. The energy input and output of glycolysis Glycolysis: - The orientation diagram at the right relates glycolysis to the whole process of respiration - Steps 1-5 are the energy investment phase of glycolysis - Ten reaction, each catalyzed by a specific enzyme, make up the process we call glycolysis - ALL organisms have glycolysis occurring in their cytoplasm. - At steps 1 and 3 ATP is converted to ADP, inputting energy into the reaction as well as attaching a phosphate to the glucose. - A
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