Ch 6 Cellular Respiration

Energy for life ECOSYSTEM Photosynthesis in chloroplasts Glucose Cellular respiration in mitochondria H2OH2O CO 2 O2O2   (for cellular work) ATP Heat energy

Breathing vs Cellular Respiration Breathing- gas exchange Cellular respiration- aerobic harvesting of energy from food molecules by cells

Cellular Respiration Energy stored in ATP C 6 H 12 O 6 + 6O2O2 Glucose Oxygen 6 CO 2 Carbon dioxide + 6 H2OH2O Water + ATPs Energy

Cell Respiration

Redox Oxidation- loss of e- Reduction- addition of e- Loss of hydrogen atoms (oxidation) 6 CO H 2 O + Energy Gain of hydrogen atoms (reduction) (ATP) C 6 H 12 O O 2

Glucose Oxidation Significant in oxidation f Glucose – Dehydrogenase – NAD +- -coenzyme, electron carrier molecule Becomes NADH ***FADH 2 H e – Oxidation Dehydrogenase Reduction NAD HNADH+ H+H+ (carries 2 electrons)

Electron Transport Chain NADH transfer e - to ETC Redox reactions as e - travel through chain O 2 final e - acceptor Energy released at each step ATP NAD + NADH H+H+ H+H+ 2e – Electron transport chain Controlled release of energy for synthesis of ATP + O2O2 H2OH2O 1212

Cell Respiration

Glycolysis Splits sugar Breaks Glucose from 6- C sugar into two 3- C sugars Yields 2 pyruvate molecules – Net gain of 2 ATP, 2 NADH, 2 H 2 O Glucose NAD ADP NADH2 P2 2 ATP 2 + H+H+ 2 Pyruvate

Glycolysis 2 Pyruvate Substrate-level phosphorylation – Transfer of P from substrate to ADP to become ATP Energy banked in ATP and NADH  ADP ATP Enzyme Product Enzyme P P P Substrate

Glycolysis 3 “phases” – Energy consuming – Glucose split – Energy producing G3P is significant intermediate – Glyceraldehyde-3-phosphate

Steps – ATP and pyruvate are produced. Step A redox reaction generates NADH. Step A six-carbon intermediate splits Into two three-carbon intermediates. Steps – A fuel molecule is energized, using ATP. Fig. 6-7c ENERGY INVESTMENT PHASE Glucose Glucose-6-phosphate 1 Fructose-6-phosphate Step ADP ATP P 3 ADP ATP P 2 P 4 P Fructose-1,6-bisphosphate 5 5 PP P P P P NAD + P P ENERGY PAYOFF PHASE Glyceraldehyde-3-phosphate(G3P) 1,3-Bisphosphoglycerate NADH NAD + NADH + H + ADP ATP Phosphoglycerate 2-Phosphoglycerate PP PP P P H2OH2OH2OH2O ADP ATP 9 9 Phosphoenolpyruvate (PEP) Pyruvate

Cannot enter Citric Acid Cycle directly 3 reactions take place 1.Carboxyl group removed, given off as CO2 2.Remaining 2-C compound oxidized, NAD+ reduced (2 NADH formed) 3.Coenzyme A combines with 2-C compound to form Acetyl Coenzyme A

Formation of Acetyl CoA Coenzyme A CoA NAD + NADH  H + CO Acetyl coenzyme A Pyruvate

Cell Respiration

Krebs Cycle AKA the Citric Acid Cycle – Mitochondrial matrix Starts with Acetyl Coenzyme A – Only Acetyl part joins cycle (2-C) – Coenzyme A is recycled Nets 2 CO2, 3 NADH, 1 FADH2 and 1 ATP per turn – 1 glucose=2 pyruvate=2 Acelty CoA=2 turns Kreb Cycle

Krebs Cycle

Cell Respiration

Oxidative Phosphorylation Stage where most ATP is produced – Membrane of mitochondria 2 parts – ETC – Chemiosmosis ETC creates gradient Chemiosmosis uses gradient to generate ATP

ATP H+H+ Intermembrane space O2O2 H2OH2O 1212 Inner mitochondrial membrane H+H+ NAD + H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ H+H+ Mitochondrial matrix Electron flow Electron carrier Protein complex of electron carriers NADH FADH 2 FAD ATP synthase P ADP + Chemiosmosis + 2 O XIDATIVE P HOSPHORYLATION Electron Transport Chain Oxidative Phosphorylation

Overall Start with 1 glucose molecule – Split into 2 pyruvate in Glycolysis – Yields 2 ATP, 2 NADH, 2 H20 2 Pyruvate converted to 2 Acetyl CoA – Yields 2 NADH Acetyl CoA enters Kreb Cycle – Yields 2 ATP, 6 NADH, 2 FADH (per glucose) Oxidative Phosphorylation – Yields 34 ATP

ATP yield Cytoplasm Glucose FADH 2 Mitochondrion Maximum per glucose: OXIDATIVE PHOSPHORYLATION (Electron Transport and Chemiosmosis) CITRIC ACID CYCLE Electron shuttle across membrane 2 NADH (or 2 FADH 2 ) 2 Acetyl CoA GLYCOLYSIS 2 Pyruvate About 38 ATP  about 34 ATP by substrate-level phosphorylation by oxidative phosphorylation  2 ATP by substrate-level phosphorylation  2 ATP

Stopping the chain Poisons can act during Oxidative Phosphorylation – Rotenone Blocks ETC by binding to e - carrier molecules – Cyanide, CO Blocks ETC by binding to e- carrier molecules O 2 cannot accept e- – Oligomycin Blocks ATP synthase – Uncouplers (DNP) Creates leaky membrane

Fig ATP H+H+ O2O2 H2OH2O 1212 H+H+ NAD + NADH FADH 2 FAD PADP + Chemiosmosis + 2 Electron Transport Chain H+H+ H+H+ H+H+ H+H+ Rotenone Cyanide, carbon monoxide H+H+ H+H+ Oligomycin ATP synthase DNP H+H+ H+H+ H+H+

Alternate Pathways Aerobic v Anaerobic Obligate anaerobes Facultative anaerobes

Fermentation Anaerobic – Allows cells to generate ATP in absence of O2 Regenerates NAD+ to break down glucose Only yields 2 ATP Lactic Acid in animal muscles Ethanol in bacteria and yeast

Fermentation Glucose NADH NAD ADP P ATP 2 NADH 2 NAD ADP P ATP2 2 Pyruvate 2 Lactate GLYCOLYSIS Lactic acid fermentation NADH NAD NADH2 NAD Pyruvate 2 Ethanol Alcohol fermentation Glucose CO 2 2 released  2  2

We eat more than just glucose Different foods enter the process at different stages Typically broken down before entering cycles

Fig Food, such as peanuts ProteinsFatsCarbohydrates Glucose O XIDATIVE P HOSPHORYLATION (Electron Transport and Chemiosmosis) CITRIC ACID CYCLE Acetyl CoA GLYCOLYSIS Pyruvate Amino acids Glycerol Sugars Fatty acids Amino groups G3P ATP

ETC ture=related ture=related Glycolysis Kreb eature=related eature=related Overview Fermentation