Download Biology Reading Guide 6 Where all energy ultimately come from Sun

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Biology Reading Guide 6 Where all energy ultimately come from Ø Sun Chemical equation photosynthesis Ø 6CO2 + H2O + energy à C6H12O6 + 6O2 Chemical equation cellular respiration Ø C6H12O6 + 6O2 à 6CO2 + H2O + energy Relationship of photosynthesis and cellular respiration Ø Opposites Respiration Ø Breathing Ø Exchange of gases Ø Aerobic Cellular respiration Ø The aerobic harvesting of energy from food molecules the energy releasing chemical breakdown of food molecules and storage of potential energy in a form that cells can use to perform work, involves glycolysis the citric acid cycle oxidative phosphorylation Ø Fundamental function is to generate ATP Ø Energy per day from food the brain and other life sustaining activities require § 75% Oxidation Ø The loss of electrons from a substance involved in a redox reaction always accompanies reduction Reduction Ø The gain of electrons by a substance involves in a redox reaction always accompanies oxidation NAD+ Ø Accepts electrons and becomes reduced to NADH Ø Nicotinamide adenine dinucleotide is an organic molecule that cells make from the vitamin niacin and use to shuttle electrons in redox reactions Transfer of electrons can be traced to the transfer of hydrogen atoms from one molecule to another Ø Each H atom can be thought of as one electron plus one H+ Ø When an atom loses and H atom then it loses and electron plus 1 H+ Ø When an atom gains an atom it gains an electron and 1 H+ § NADH à NAD+ = Reduction Main stages of cellular respiration Ø Glycolysis Ø Citric acid cycle Ø Oxidative phosphorylation Stage Glycolysis Krebs Cycle Oxidative phosphorylation ETC Chemiosmosis Reactants Glucose Products 2 molecules pyruvate 2 carbon acytl co-­‐A 4 ATP 10 NADH 2FADH2 Location NADH FADH2 ADP Mitochondrial matrix Mitochondrial matrix NAD ADP ATP Mitochondrial matrix v Glycolysis Ø Initial # glucose molecules: 1 Ø # ATP molecules invested: 2 Ø # ATP molecules produced: 4 Ø # Net ATP molecules: 2 Ø # NADH produced: 2 Ø # Pyruvate molecules/glucose: 2 v Substrate level phosphorylation Ø The formation of ATP by an enzyme directly transferring a phosphate group to ADP from an organic molecules v Where is glycolysis Ø Cytoplasmic fluid of the cell v Can cell energy NADH be used immediately Ø No electrons from NADH must pass down an electron transport chain located in the inner mitochondrial membrane v Where citric acid cycle occur Ø Mitochondrial matrix Ø Inner membrane v Oxidative phosphorylation 2 steps Ø Electron transport chain Ø Chemiosmosis v What can go wrong Ø ETC § Poison rotenone binds tightly with electron carrier molecules in 1st protein complex preventing electrons from passing to next carrier molecules by blocking ETC near the start and thus preventing ATP synthesis it starves organisms cells of energy § Cyanide and carbon monoxide bind to electron carrier 4th protein complex block passing electrons to oxygen electrons no longer flow though “pipe” no H+ gradient is generated and no ATP is made Ø Chemiosmosis § DNP all except chemiosmosis in cellular respiration run, so most all energy is lost Ø Mitochondrial membrane § Uncouples make mitochondrial membrane leaky to hydrogen ions electron transport continues normally but ATP cannot be made because the leakage of H+ through membrane destroys the H+ gradient cells continue to burn fuel and consume oxygen often at a higher than normal rate but cannot make any ATP through chemiosmosis because no H+ gradient exists v Regulation Ø Supply/demand Ø Excess = pathway for synthesis goes off Ø Feedback inhibition – end product inhibits an enzyme that catalyzes an early step in the pathway also controls cellular respiration of ATP accumulate in cell then inhibits early enzyme glycolysis – slow down respiration reserve resources v Fermentation produced ATP without oxygen v Lactic acid fermentation Ø Glycolysis followed by the reduction of pyruvate to lactate regenerating NAD+ v Alcohol fermentation Ø Glycolysis followed by the reduction of pyruvate to ethyl alcohol regenerating NAD+ and releasing CO2 v Anaerobes Ø Obligate anaerobes § Require anaerobic conditions – poisoned by oxygen Ø Facultative anaerobes § Make ATP either by fermentation or by oxidative phosphorylation depending if O2 available • Wine/beer Oxidative Phosphorylation Citric Acid ETC Chemiosmosis