CO 2 + H 2 O Photosynthesis (plants, algae, cyanobacteria) C 6 H 12 O 6 + O 2 Cellular Respiration (Eukaryotic cells) CO 2 + H 2 O

Cellular Respiration (requires O 2 and gives off CO 2 ) Breakdown of glucose in the presence of oxygen to yield large amounts of ATP Occurs in the cytoplasm and mitochondria of eukaryotic cells C 6 H 12 O 6 + 6O 2  6CO 2 + 6H 2 O + (36 ATP) (what is oxidixed?reduced?) Exergonic reaction- high energy molecule, glucose, produces low energy molecules; 39% efficient What do cells do with the ATP?

Cellular Respiration Occurs in 4 Phases Stage I: Glycolysis (cytoplasm) Stage II: Prep Stage (mitochondrial matrix) Stage III: Citric Acid Cycle (mitochondrial matrix) Stage IV: Electron Transport Chain  oxidation- reduction reactions using NADH, FADH 2 (mitochondrial cristae)

Stage I: Glycolysis Ancient universal reaction Breakdown of glucose  2 pyruvates Occurs in the cytoplasm; outside of mitochondria Anaerobic Requires an initial energy (2 ATPs) investment 4 ATPs are made by substrate level phosphorylation (ATP synthesis) Net Yield: 2 ATPs, 2 NADHs Substrate level ATP synthesis; coupled reactions

NAD + = redox coenzyme, carries electrons to ETC when O2 is available and is reused. Substrate level ATP synthesis When O2 is not available fermentation occurs, with a net yield of 2 more ATP

Stage II: Prep Stage Pyruvate  Acetyl CoA Occurs in the mitochondria (matrix) Releases 2 CO 2 Makes 2 NADH

Stage III: Citric Acid Cycle A circular enzyme driven metabolic pathway that generates coenzymes and ATP Occurs in the mitochondria (matrix) Starts with the combination of oxaloacetate + Acetyl CoA  citrate 2 turns = 2 ATPs, 6 NADH, 2 FADH 2 are made 4 CO 2 are released; Glucose has been converted to 6 CO2- 2 in prep, 4 in Citric acid cycle Substrate level ATP synthesis

Stage IV: Electron Transport Chain (ETC) Movement of electrons through a series of coenzyme/protein redox reactions to yield large amounts of ATP; electrons fall from hydrogen to oxygen releasing energy Electrons (e-) are donated from NADH, FADH 2 to the ETP As, e- move through the ETP, they attract H+ ions to the outer compartment of mitochondria

Stage IV: ETC and Chemiosmosis A electrical and H+ concentration gradient is created (10x) H+ ions must move back from a higher  lower concentration Only return to inner compartment through ATP synthases, “gates of the dam” As they move through, activate ATP synthase to make ATP from ADP + Pi This process is called Chemiosmosis (ATP production linked to H+ gradient) 1 minute reserve of ATP

Stage IV-ETC The coenzymes NADH and FADH 2 give up electrons to the ETP The higher up in the ETP, the more energy released by those e- 1 NADH = 3 ATP, 1 FADH 2 = 2 ATP The final electron acceptor is O 2, which combines with H+ ions to form H 2 O How many ATPs are made through the ETC?

Total ATP Yield during Cellular Respiration: Molecular Bookkeeping Glycolysis: 2 NADH, 2 ATP Prep stage: 2 NADH Citric Acid Cycle: 6 NADH, 2 FADH2, 2 ATP ETC: 34 ATP (but, substract 2 ATP from total to account for NADH brought in from cytoplasm) = 32 ATP net ATP yield from the complete breakdown of 1 glucose = 36 ATP 38 ATP in liver, heart, kidney cells

Anaerobic Respiration: A Comparison to Aerobic Respiration Anaerobic respiration Breakdown of glucose No oxygen required Low ATP yield Quick energy yield Starts and finishes in cytoplasm Bacteria, muscle, yeast cells Cellular respiration Breakdown of glucose Oxygen required High ATP yield Slow energy yield Starts in cytoplasm Finishes in mitochondria Animal, plant cells

Anaerobic Respiration: Lactic Acid Fermentation Pyruvate  lactate + 2 ATP Occurs in absence of O2 Lactobacillus (dairy products) and muscle cells Quick, low energy yield Wastes glucose, pyruvate cannot enter into Citric Acid Cycle

Anaerobic Respiration: Alcoholic Fermentation Pyruvate  ethanol + CO 2 Occurs in absence of O 2 Low ATP yield, wastes pyruvate (glucose) Yeast cells (baking) and production of beer and wine

Metabolic Pool Concept Human diet consists of other macromolecules such as proteins and fats. What happens to them? Which of the biomolecules gives the cell the most ATP when completely broken down? How much ATP would be made from a 18 carbon fatty acid? 9 Acetyl CoA? Catabolism  degradation Anabolism  synthesis

Compare and Contrast Photosynthesis to Cellular Respiration