3 parts of Respiration Glycolysis – may be anaerobic TCA – Kreb’s Cycle Electron Transport Chain aerobic – require oxygen

Electron Transport Chain a.k.a cytochrome chain Main ATP producer! Chemiosmotic theory explains how the cytochrome chain produces ATP Step 1: creating a H+ concentration gradient Step 2: using the gradient to make ATP

Creating a Potential Carrier molecules (cytochromes) in the inner membrane transport H+ out; accumulates in the intermembrane space Creates an electrochemical gradient!

Click here for ETC Click here for ATP synthase close-up

Creating a Potential NADH and FADH2 bring H atoms to the chain. e- are stripped off and passed down the chain of cytochromes Oxygen becomes the final electron acceptor to form water. http://vcell.ndsu.edu/animations/etc/movie-flash.htm

Using the gradient to make ATP http://vcell.ndsu.edu/animations/atpgradient/movie-flash.htm

Glycolysis Citric acid cycle Electron shuttles span membrane CYTOSOL MITOCHONDRION 2 NADH or 2 FADH2 2 NADH 2 NADH 6 NADH 2 FADH2 Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis 2 Acetyl CoA Citric acid cycle 2 Pyruvate Glucose + 2 ATP + 2 ATP + about 32 or 34 ATP Summary Respiration starts with glycolysis. This occurs in the cytosol. One glucose molecule is split to produce 2 pyruvate molecules. In the process, 2 NADH and 2 ATP molecules are produced. NADH carries energy into the mitochondrion to fuel other steps. Glycolysis enters the matrix of the mitochondrion. Prior to entering the Krebs Cycle, pyruvate must be converted into acetyl CoA (pronounced: acetyl coenzyme A). This is achieved by removing a CO2 molecule from pyruvate and then removing an electron to reduce an NAD+ into NADH. An enzyme called coenzyme A is combined with the remaining acetyl to make acetyl CoA which is then fed into the Krebs Cycle. What happens to the NADH2+ and FADH2 produced during the Krebs cycle? The molecules have been reduced, receiving high energy electrons from the pyruvic acid molecules that were dismantled in the Krebs Cycle. Therefore, they represent energy available to do work. These carrier molecules transport the high energy electrons and their accompanying hydrogen protons from the Krebs Cycle to the electron transport chain in the inner mitochondrial membrane. Once the electrons (originally from the Krebs Cycle) have yielded their energy, they combine with oxygen to form water. If the oxygen supply is cut off, the electrons and hydrogen protons cease to flow through the electron transport system. If this happens, the proton concentration gradient will not be sufficient to power the synthesis of ATP. This is why we, and other species, are not able to survive for long without oxygen! by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol About 36 or 38 ATP Maximum per glucose:

Anaerobic Respiration (fermentation) Require the energy-carriers formed by glycolysis Alcholic fermentation Lactic Acid fermentation

Alcoholic Fermentation Performed by yeast cells If NADH can’t dump e- into ETC, it dumps them back into pyruvate; making it the electron acceptor! NAD+ is restored and recycles back into glycolysis  yielding only 2 ATP molecules Pyruvate will eventually become ethanol (which is an alcohol, hence alcoholic fermentation… DUH!)

Alcoholic Fermentation Alcoholic fermentation is similar to lactic acid fermentation. glycolysis splits glucose and the products enter fermentation energy from NADH is used to split pyruvate into an alcohol and carbon dioxide NADH is changed back into NAD+ NAD+ is recycled to glycolysis

Lactic Acid Fermentation Occurs in muscle cells Similar to alcoholic fermentation where pyruvate becomes the final electron acceptor Pyruvate is converted to lactic acid

Lactic Acid Fermentation Lactic acid fermentation occurs in muscle cells. glycolysis splits glucose into two pyruvate molecules pyruvate and NADH enter fermentation energy from NADH converts pyruvate into lactic acid NADH is changed back into NAD+

Energetics of Respiration Aerobic vs. Anaerobic: Which is more efficient? Aerobic: yields 38 ATP per glucose molecule Anaerobic: yields 2 ATP per glucose molecules Anaerobic is not as efficient, but still allows you to live without oxygen

Alternative Food Molecules Fats and proteins can change form that can enter normal respiration pathways Fats Glycerol enters glycolysis Fatty acids into acetyl-CoA Proteins Deaminated, remainder enters at various points in the chain