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
oxidized form
reduced form
reduced form
oxidized form
Cellular Respiration Overview• Occurs mainly in mitochondria (begins in cytoplasm)1. Glycolysis
1. “Prep Step”2. Krebs Cycle (Citric Acid Cycle)3. Oxidative Phosphorylation & Chemiosmosis (ETC)
LEARNING TARGET 2
I can explain how glycolysis harvests chemical energy by oxidizing glucose into pyruvate.
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+
LEARNING TARGET 3
I can explain how the citric acid (Krebs) cycle completes the energy yielding oxidation of organic molecules.
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 process1. Carboxyl group (COO) is removed
from pyruvate• Releases 1 CO2 (per pyruvate)
2. Remaining 2C fragment is oxidized, producing acetate and NADH• Creates 1 NADH (per pyruvate)
3. 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 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