Cellular Respiration C6H12O6 + 6 O2 6 CO2 + 6H2O + 38 ATP

Cellular Respiration: An Overview Process by which cells convert the energy in food (usually glucose) into usable ATP. Terms to Know… Oxidation = the loss of electrons Compound becomes more positive Reduction = the gain of electrons Compound becomes more negative Electrons and protons (H+) travel TOGETHER NAD+ = coenzyme derived from niacin; acts as a H+ and e- acceptor. AN ENERGY CARRIER!

Cellular Respiration: An Overview

Substrate-Level Phosphorylation An enzyme transfers a phosphate group directly from an organic molecule to ADP to form ATP The ATP produced in Glycolysis & the Krebs Cycle is produced by this method.

Oxidative Phosphorylation (ETC + Chemiosmosis) The production of ATP by using energy derived from the redox reactions of the Electron Transport Chain. The enzyme ATP synthase is needed to phosphorylate the ADP to produce ATP. Almost 90% of the ATP produced from cellular respiration is produced this way.

Anaerobic Respiration Cellular Respiration Glucose Glycolysis ATP Oxygen Absent Oxygen Present Anaerobic Respiration (Fermentation) Aerobic Respiration (Krebs Cycle & ETC) ATP

Glycolysis “glucose-splitting” Big Picture: Occurs in the cytosol Glucose (6-C) is broken down into 2 molecules of pyruvate (3-C) Occurs in the cytosol Occurs with or without oxygen Made up of 2 phases: Energy investment phase Energy yielding phase

Glycolysis: Energy Investment Phase Glucose is converted into 2 G3P (Glyceraldehyde-3-phosphate) Requires 2 ATP

Glycolysis: Energy-Yielding Phase 2 G3P are converted into 2 Pyruvate (3C) molecules. Dehydrogenase enzymes remove H from intermediate compounds and attach them to 2 NAD to produce 2NADH

Net Gain in Glycolysis 2 ATP 2 NADH - 2 ATP (Energy investment phase) + 4 ATP (Energy yielding phase) + 2 ATP 2 NADH Electron carriers Will be used to make ATP later 

Choices, Choices!  If oxygen is absent, anaerobic respiration occurs Fermentation Yeast & some bacteria  alcoholic fermentation Animal muscle lactic acid fermentation If oxygen is present, aerobic respiration occurs Krebs Cycle and Electron Transport Chain

Anaerobic Respiration Cellular Respiration Glucose Glycolysis ATP Oxygen Absent Oxygen Present Anaerobic Respiration (Fermentation) Aerobic Respiration ATP

Fermentation 2 major types: Alcoholic and lactic acid fermentation NAD+ acts as a hydrogen acceptor during glycolysis If the supply of NAD+ runs out, then glycolysis would have to stop. Fermentation occurs as simply a means of recycling the NAD+, so that glycolysis can occur again.

Alcoholic Fermentation Occurs in some BACTERIA and YEAST 2 step process: Carbon dioxide is released from pyruvate (3-C), forming acetaldehyde (2-C) Acetaldehyde is reduced by NADH (gains an electron), forming ethyl alcohol (ethanol) NAD+ is regenerated, thereby allowing glycolysis to continue Used to produce beer and wine

Lactic Acid Fermentation Occurs in ANIMALS 1 step process: Pyruvate is reduced by NADH (gains an electron), forming lactic acid NAD+ is regenerated, thereby allowing glycolysis to continue Occurs in muscle cells, causing muscle pain and fatigue

Anaerobic Respiration Cellular Respiration Glucose Glycolysis ATP Oxygen Absent Oxygen Present Anaerobic Respiration (Fermentation) Aerobic Respiration ATP

Aerobic Respiration After glycolysis, most of the energy from glucose remains “locked” in 2 molecules of pyruvate If oxygen is present, the pyruvate enters the mitochondrial matrix to complete the Krebs Cycle Pyruvate (3-C) is converted to Acetyl CoA (2-C) CO2 is released as a waste product NADH is produced

The Krebs Cycle Yield per pyruvate molecule: 4 NADH 1 FADH2 1 ATP 2 CO2 Yield per glucose molecule (two turns of Krebs Cycle): 8 NADH 2 FADH2 2 ATP 6 CO2 CO2 released as a waste product

Electron Transport Chain The ETC converts the NADH and FADH2 from glycolysis and the Krebs Cycle into ATP Occurs in inner membrane of mitochondrion The energy in each NADH molecule moves enough protons (H+) into the mitochondrial matrix to create 3 ATP 1 FADH2  2 ATP

The Electron Transport Chain The electrons from NADH and FADH2 are passed from one electron acceptor molecule to another. Each electron acceptor is more electronegative than the last. Oxygen is the final electron acceptor e- ETC oxygen

Chemiosmosis Similarly to photosynthesis, the energy the electrons lose along the way moves H+ out of the matrix and into the intermembrane space of the mitochondrion As H+ ions diffuse through the membrane, ATP synthase uses the energy to join ADP and a phosphate group  ATP

Oxidative Phosphorylation: ETC & Chemiosmosis

Aerobic Respiration: Total Energy Yield Glycolysis: 2 ATP (Net) 2 NADH  6 ATP Krebs Cycle: 2 ATP 8 NADH  24 ATP (ETC) 2 FADH2  4 ATP (ETC) TOTAL: 8 ATP + 30 ATP  38 ATP