Transcript Biology 105
Biology 105 Chapter 8: How cells make ATP Pgs 172-191 Student Outcomes Give an overview and analysis of the 4 stages of aerobic respiration Describe the process by which the proton gradient drives ATP synthesis Student Outcomes Summarize how the products of protein and lipid catabolism enter the same metabolic pathway that oxidizes glucose. Describe the energy captured in each state of aerobic respiration. Respiration Organismic respiration - process of gas exchange between body and the environment. Cellular respiration - process of converting food energy to chemical energy Cellular respiration Two types: Aerobic - requires oxygen Anaerobic - absence of oxygen, includes fermentation Both types are exergonic reactions (release free energy) Stage 1 of aerobic respiration of glucose • Known as glycolysis • Takes place in the cytosol • Glucose molecule is converted to two 3carbon molecules of pyruvate • ATP and NADH are formed Stage 1 of aerobic respiration of glucose cont. Glycolysis can occur in either aerobic/anaerobic conditions Glycolysis has 2 phases Glycolysis 1st phase requires energy (ATP) - endergonic reactions. (energy investment phase) A phosphate is transferred from ATP to the sugar. (phosphorylated) Glycolysis formula Glucose + ATP -> 2 G3P + 2 ADP ATP- Adenosine Triphosphate ADP- Adenosine Diphosphate G3P- glyceraldehyde-3-phosphate Glycolysis 2nd phase- (energy capture phase) Each G3P is converted to pyruvate (a 3 carbon compound) 2 NADH and 4 ATP molecules are produced per glucose molecule. 2G3P + 2NAD +4ADP -> 2 Pyruvate + 2NADH + 4 ATP Formation of acetyl Coenzyme A (CoA) 2nd stage Takes place in the mitochondria NAD+ gains an electron and becomes ‘reduced’ to NADH 2 additional NADH are formed per glucose molecule 2 CO2 molecules are produced Citric Acid Cycle 3rd stage - also known as the Krebs cycle (founder Hans Krebs) Takes place in the mitochondria 3 molecules of NADH, 1 FADH2 and 1 ATP are formed from each acetyl CoA molecule. Two CoA molecules were formed after the 2nd stage. This results in double the products. ATP synthesis 4 ATP produced so far 2 ATP net in glycolysis 2 ATP in the citric acid cycle Electron transport chain 4th stage - takes place in the mitochondria Results in chemiosmosis - formation of ATP as protons diffuse through transmembrane channels. This process is known as oxidative phosphorylation Results in 32-34 ATP formed Body Heat Most heat generated by a warmblooded organism (and some others) is through heat generated as a byproduct of the electrons moving down the electron chain. Acceptor molecules are reduced and oxidized creating small amounts of heat! Total ATP 36-38 ATP produced by one molecule of glucose in aerobic respiration. 36 in muscle, brain cells due to more energy needed to perform the 4 stages. Loss of 2 ATP’s Other Energy sources Fatty acids and amino acids 1 glucose molecule = 36-38 ATPs 1 Lipid molecule = 44 ATPs Anaerobic Respiration Does not use oxygen Electrons are transferred as glucose is broken down to NADH. Fermentation No electron transport chain stage. Ethyl Alcohol or lactate (lactic acid) are produced as a byproduct (toxic to cells) Lactate is used to make yogurt, sauerkraut and Kimchee. 2 ATP’s produced from 1 molecule of glucose. Lactate 3 carbon compound 80% regenerated into glucose by the liver. 20% is metabolized in the muscle cells if oxygen is present. (this is why heavy breathing occurs for a short time after activity) Lactate fermentation Short bursts of energy Once believed that the accumulation of lactate (lactic acid) in the muscle cells results in muscle cramps, fatigue and pain Creatine Phosphate CP - Found in muscle cells and aids in the formation of ATP from ADP Has short energy span 1-10 seconds, but will regenerate every 2-3 minutes Energy use 1 second to 10 seconds (Anaerobic and CP) 10 seconds to 1 minute (Anaerobic) 1 minute - 4 minutes (Anaerobic/Aerobic) 4 minutes + (Aerobic)