Unformatted text preview: Bio – 1510 Basic Life Mechanisms Bio fall 2008
Dr. Rasheeda Zafar Chapter # 7 How Cells Harvest How Energy Energy
1 Respiration Respiration All organisms use cellular respiration to extract energy from organic molecules Autotrophs Autotrophs Produce their own organic molecules through photosynthesis Heterotrophs Heterotrophs
organisms Live on organic compounds produced by other 2 Respiration Respiration Cellular Respiration Series of reactions Oxidations – loss of electrons Dehydrogenations – lost electrons are accompanied by hydrogen Therefore, what is actually lost is a Therefore, hydrogen atom (1 electron, 1 proton). hydrogen 3 Respiration Respiration During redox reactions(oxidation-reduction), electrons carry energy from one molecule to another.
+ 4 Oxidation - Reduction Oxidation 5 Respiration Respiration During respiration, electrons are shuttled through electron carriers to a final electron acceptor.
2 Aerobic respiration final electron receptor is oxygen 6 Aerobic Respiration Aerobic
6 12 6 2 2 2 7 Respiration Respiration ATP Production ATP Oxidation reaction Releases energy in the form of electrons Electrons shuttled by
+ 8 Oxidation of Glucose Oxidation Cells make ATP Cells Substrate level phosphorylation Substrate Transferring a phosphate directly
to ADP from another molecule Oxidative phosphorylation Oxidative Use of ATP synthase (enzyme) and
energy derived from a proton (H+) gradient to make ATP 9 Oxidation of Glucose Oxidation Stages of Glucose Oxidation Stages Glycolysis Pyruvate Oxidation Krebs Cycle Electron Transport Chain & chemiosmosis 10 Aerobic Respiration Aerobic 11 Glycolysis Glycolysis Glucose converted to pyruvate Glucose 10-step biochemical pathway Occurs in cytoplasm 2-molecules of pyruvate are formed Net production of 2 ATP molecules by substrate-level phosphorylation substrate-level 2 NADH produced by reduction of
+ 12 Glycolysis Glycolysis 13 Glycolysis Glycolysis For glycolysis to + continue,NADH must 14 15 Glycolysis Glycolysis Pyruvate Pyruvate Presence of oxygen Presence Oxidized to Oxidized acetyl Co – A acetyl To Kreb’s cycle To Absence of oxygen Absence Reduced in order to oxidize NADH back oxidize
+ 16 Pyruvate Oxidation Pyruvate Occurs in mitochondria in eukaryotes Occurs at the plasma membrane in prokaryotes Pyruvate dehydrogenase Pyruvate (multicomplex enzyme) catalyses the reaction
2 17 Krebs Cycle Krebs Occurs in mitochondrial matrix Oxidizes the acetyl group from pyruvate Biochemical pathway of 9 steps steps First step acetyl group + oxaloacetate (2 carbons) + (4 carbons) citrate (6 carbons) 18 Krebs Cycle Krebs Remaining steps of Krebs Cycle
2 19 Krebs Cycle Krebs 20 Krebs Cycle Krebs 21 Krebs Cycle Krebs Conclusion of glucose oxidation Glycolysis Pyruvate oxidation Krebs cycle
2 22 Electron Transport Chain (ETC) (ETC) Series of membrane
bound electron carriers Embedded in the mitochondrial mitochondrial inner membrane inner Electrons from NADH and
2 23 ETC ETC ubiqunome 24 Electron Transport Chain Electron The higher negative charge in the matrix attracts the
+ 25 ATP Rotary Engine ATP 26 Mitochondria Mitochondria 27 Electron Transport Chain Electron Most protons move back to the matrix through ATP synthase. synthase ATP synthase is a membrane-bound enzyme that uses the energy of the proton gradient to synthesize ATP from ADP + Pi.
28 Energy Yield of Respiration Energy Theoretical energy yields yields Bacteria 38 ATP per glucose molecule Eukaryotes 36 ATP 36 per glucose molecule Actual Actual energy yield Eukaryotes 30 ATP per glucose molecule Reduced yield is due to “leaky” inner membrane and use of the proton gradient for purposes other than ATP synthesis 29 Regulation of Respiration Regulation Aerobic respiration Feedback inhibition Feedback A step within glycolysis is allosterically inhibited by ATP and citrate High levels of NADH inhibit puruvate dehdrogenase High levels of ATP inhibit citrate synthetase 30 Oxidation without Oxygen Oxidation Anaerobic respiration
2 31 Anaerobic Respiration Anaerobic Methanogens Methanogens
2 32 Fermentation Fermentation Reduces organic molecules in
+ 33 Catabolism of Protein and Fat Catabolism Catabolism of proteins: Catabolism Amino acids undergo deamination deamination Removes amino group Remainder of the amino acid is converted to a molecule that enters glycolysis or the Krebs cycle Example Alanine is converted to pyruvate Aspartate is converted to oxaloacetate
34 Catabolism of Proteins and fat Catabolism Catabolism of fats: Fats are broken down to fatty acids and glycerol Fatty acids are converted to acetyl groups by β-oxidation -oxidation The respiration of a 6-carbon fatty acid yields 20% more energy than glucose. 35 Beta Oxidation 36 Extraction of Chemical Energy Extraction 37 Evolution of Metabolism Evolution A hypothetical timeline for the evolution of metabolism Ability to store chemical energy in ATP Evolution of glycolysis
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