If Oxygen is available, pyruvic acid can continue through aerobic respiration inside the mitochondria
Pyruvic Acid (3 Carbon)
Aerobic Pathways Include: 1. Acetyl CoA synthesis 2. Citric Acid Cycle 3. Electron Transport Chain (ETC)
Mitochondria
Mitochondria • Powerhouse of cell • Synthesizes ATP • 2 layers – Outer Membrane – Inner Membrane
• Cristae • highly folded inner membrane • Greatly increases surface area for reactions
Synthesis of Acetyl CoA Pyruvic Acid is converted into Acetyl CoA Acetyl CoA = substrate for Citric Acid Cycle
Synthesis of Acetyl CoA Pyruvic Acid (3 Carbon) 1 carbon is lost as CO2
CO2 (waste) Acetic Acid (2 Carbon)
CoA
Acetyl CoA (Enters Citric Acid Cycle)
(coenzyme A)
Products from Acetyl CoA Synthesis • 1 molecule of CO2 • Acetyl CoA
Citric Acid Cycle Begins when Acetyl CoA combines with Oxaloacetic Acid to form Citric Acid. Acetyl CoA + Oxaloacetic Acid → Citric Acid (2 carbons) (4 carbons) (6 carbons) Citric Acid = Start molecule of cycle
Oxaloacetic acid = end molecule of cycle
Citric Acid is converted back to Oxaloacetic acid through a series of 8-9reactions
Acetyl CoA (2 carbons)
+
Oxaloacetic Acid (4 carbons)
Oxaloacetic acid is regenerated
Citric Acid (6 Carbons)
2CO2 (waste)
Citric Acid Cycle
2ADP
8-9 reactions
FADH2
2 ATP FAD 3 NADH
3NAD+
Products of Citric Acid Cycle • • • •
2 ATP 3 NADH = transports electrons to ETC 1 FADH2 = transports electrons to ETC 2 CO2
Electron transport chain (ETC) • • • • •
Occurs on inner membrane of mitochondria ATP synthase (enzyme): phosphorylates ADP → ATP Involves a chain of 3 enzymes (protein complexes) Produces 32-34 ATP per glucose Requires Oxygen to accept electrons
Enzyme Complexes in ETC • Transport Complex Proteins – 3 Membrane proteins on inner membrane of Mitochondria – NADH & FADH2 transfer electrons to complex proteins – Electrons are passed from one complex to the next complex – Transfer of electrons releases energy to power ATP Synthase
• ATP Synthase – Phosphorylates ADP into ATP – Powered by Transport Complex Proteins
ADP +
P
ATP Synthase
ATP
2 electrons
energy
NADH energy Complex I
energy Complex II
NAD+
2H+
(reused)
Complex III
+ ½ O2
H2O
(final electron acceptor)
Without Oxygen to accept electrons, ETC would grind to a halt!
Products of Electron Transport Chain • H 2O • 32-34 ATP
Lipids & Proteins can also be broken down for ATP synthesis
Summary of catabolism of proteins, fats, & carbohydrates
Most common entry point to aerobic respiration is into citric acid cycle as acetyl coA
End of Section 3, Chapter 4