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Intro to Cellular Respiration, Glycolysis & Krebs Cycle. Chapter 9.1-9.3. I can explain how catabolic pathways yield energy by oxidizing organic fuels. Learning target 1. Cellular Respiration. C 6 H 12 O 6 + 6 O 2 6 CO 2 + 6 H 2 O + energy (ATP)
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Intro to Cellular Respiration, Glycolysis & Krebs Cycle Chapter 9.1-9.3
I can explain how catabolic pathways yield energy by oxidizing organic fuels. Learning target 1
Cellular Respiration • C6H12O6 + 6 O2 6 CO2 + 6 H2O + energy (ATP) • Type of coupled oxidation-reduction (redox) reaction • OIL RIG • Oxidation Is Losing electrons • Reduction Is Gaining electrons
Electron Carrier Molecules • B-vitamin coenzymes • NAD++ 2H → NADH + H+ • FAD + 2H FADH2 reduced form oxidized form reduced form oxidized form
Cellular Respiration Overview • Occurs mainly in mitochondria (begins in cytoplasm) • Glycolysis • “Prep Step” • Krebs Cycle (Citric Acid Cycle) • Oxidative Phosphorylation & Chemiosmosis (ETC)
I can explain how glycolysis harvests chemical energy by oxidizing glucose into pyruvate. Learning target 2
1. Glycolysis • “glykos” = sweet; “lysis” = split apart • Occurs in cytosol • Aerobic or anaerobic process • Glucose is oxidized into2 pyruvate • Requires 2 ATP to get started • Produces 4 ATP (net gain 2 ATP) • Produces 2 NADH
Summary of Glycolysis • One glucose (6C) converted into two pyruvates (3C) • Net yield of 2 ATP • 2 NAD+ are reduced into 2 NADH & 2 H+
I can explain how the citric acid (Krebs) cycle completes the energy yielding oxidation of organic molecules. Learning target 3
Oxidation of Pyruvate to Acetyl CoA(“Prep Step”) • Preps pyruvate for Krebs Cycle (linking glycolysis and citric acid cycle) • Occurs in mitochondria • 3 step oxidation process • Carboxyl group (COO) is removed from pyruvate • Releases 1 CO2 (per pyruvate) • Remaining 2C fragment is oxidized, producing acetate and NADH • Creates 1 NADH (per pyruvate) • Coenzyme A attaches to acetate, forming Acetyl CoA • Forms 1 Acetyl CoA (per pyruvate)
“Prep” Step Summary • Started with 2 pyruvates • Ended with: • 2 CO2 released to air, • 2 NADH that will go to ETC, and • 2 Acetyl CoA molecules (2 C) that will move on to Krebs Cycle in the mitochondrial matrix
2. Krebs Cycle (AKA Citric Acid Cycle) • Complete oxidation of glucose • Cycle because it occurs twice – once for each Acetyl CoA • 8 step pathway occurring in mitochondrial matrix • Each catalyzed by specific enzyme • Step-wise catabolism of 6C citrate molecule • All remaining H, O, and C from glucose released
Krebs Cycle Summary • At the end of 2 turns of the Krebs cycle: • 6 NADH are generated • 2 FADH2are generated • 2 ATP are generated • 4 CO2are released • If the yield is only 2 ATP, then why? • Value of NADH and FADH2 • Krebs cycle produces large quantities of these electron carriers, which are reduced molecules and store energy that will go to the ETC • ETC will produce mass ATPs
