Intro to Cellular Respiration, Glycolysis & Krebs Cycle Chapter 9.1-9.3

Review Ecology (Unit 2) Cellular Biology (Unit 4) Heterotrophs get free energy by eating other organisms Autotrophs make their own free energy from the sun Cellular Biology (Unit 4) Mitochondria are specialized organelles for energy capture and transformation

Catabolic pathways yield energy by oxidizing organic fuels Section 9.1

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 GOAL: produce ATP (usable, free energy for the cell) Occurs mainly in mitochondria (begins in cytoplasm) Glycolysis “Prep Step” Krebs Cycle (Citric Acid Cycle) Oxidative Phosphorylation & Chemiosmosis (ETC)

Addition of a Pi to ADP happens 2 ways Substrate level phosphorylation Addition of phosphate group directly without a proton gradient and ATP Synthase Enzyme-catalyzed reaction transfers Pi to ADP Found in glycolysis and Krebs cycle Oxidative phosphorylation Using proton gradient created by ETC in cristae membrane to make ATP ETC + Chemiosmosis = oxidative phosphorylation

Glycolysis harvests chemical energy by oxidizing glucose to pyruvate Section 9.2

1. Glycolysis “glykos” = sweet; “lysis” = split apart Occurs in cytosol Aerobic or anaerobic process Glucose is oxidized into 2 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+

After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules Section 9.3

Oxidation of Pyruvate to Acetyl CoA (“Prep Step”) Preps pyruvate for Krebs Cycle (linking glycolysis and citric acid cycle) Pyruvates are transported into the mitochondria 3 step oxidation process Each pyruvate Releases 1 CO2 (2 total per glucose) Makes 1 NADH (2 total per glucose) Sends 1 Acetyl CoA to Krebs Cycle

“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 FADH2 are generated 2 ATP are generated 4 CO2 are 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

Glucose is now completely oxidized

Count the carbons!