Cellular Respiration

• The chemical energy from food molecules is harvested by metabolic pathways including cellular respiration and fermentation
• Aerobic cellular respiration is the mechanism by which foods are combined with oxygen producing carbon dioxide, water, and energy
• Cellular respiration is an oxidation-reduction (redox) reaction; glucose is oxidised and oxygen becomes reduced
• NAD is a coenzyme which functions as an electron transporter; NAD+ receives 2 electrons and 1 protons from substrates to become reduced to NADH
• Cellular respiration involves 4 steps: glycolysis, pyruvate transformation to acetyl coenzymes A, Krebs / Citric acid cycle, and electron transport chain
• Step 1 Glycolysis: The breakdown of simple building blocks which occurs in the cytoplasm. Glucose is broken down into 2 3C sugars which are oxidized and rearranged to form 2 pyruvate molecules. The first phase uses 2 ATP and the second phase produces 4 ATP. NADH carries electrons to ETC
• Step 2 Pyruvate Transformation to Acetyl CoA: 2 Pyruvate (3C) enter the mitochondria and is converted to Acetyl CoA (2C) with CO2 & NADH. Acetyl CoA enters Krebs cycle
• Step 3 Krebs Cycle: 8 steps producing 3 NADH, ATP, 2 CO2, and FADH2. NADH and FADH2 are passed to the ETC to produce more ATP
• Step 4 ETC: Breaks the fall of electrons to oxygen into a series of smaller steps, releasing energy to allow ATP production. The chemical energy is converted to a form used to drive oxidative phosphorylation. Consists of molecules in the inner mitochondrial membrane which form multiprotein complexes and a proton gradient. The 1st molecule is the Flavin Mononucleotide. Eventually they pass to oxygen which picks up protons from the mitochondrial matrix and water is formed.
• Chemiosmosis occurs when the coupling of electron transport to oxidative phosphorylation
• Oxidative Phosphorylation / ATP Synthesis: ATP synthase is a protein spanning the inner mitochondrial membrane. It catalyses ATP formation from ADP and a phosphate group. The energy is derived from the proton gradient across the inner mitochondrial membrane
• Fermentation: Occurs after glycolysis in low oxygen conditions and can produce ethanol or lactic acid
• C6H12O6 + 6O2 --> 6CO2 + 6H2O + Energy