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

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 Overview Respiration starts with glycolysis. This occurs in the cytosol (cytoplasm). 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 (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:

Glycolysis Occurs in the cytoplasm (cytosol) Refer to handout…

Glycolysis

Glycolysis 1. Phosphorylate glucose – 2 ATP used up

Glycolysis 2. Rearrange molecule to form fructose

Glycolysis 3. Phosphorylate again – ATP used up Diphosphate = bisphosphate

Glycolysis 4. Split into two 3-carbon pieces, each containing one P 2 glyceraldehyde 3-phosphate (G3P) or PGAL

Glycolysis 5. Add a high-energy phosphate (~ P ) to each piece. NAD+ is reduced to NADH + H

Glycolysis 6. Transfer the high-energy phosphate to ADP, making ATP (2 are made)… substrate-level phosphorylation!

Glycolysis 7. Rearrange the position of the remaining phosphate

Glycolysis 8. Remove H2O, making phosphoenolpyruvate which contains ~ P

Glycolysis 9. Transfer high-energy phosphate (~ P ) to ADP, making ATP; 2 ATPs are made PEP becomes pyruvate

Glycolysis Click here to view a different animation http://www.science.smith.edu/departments/Biology/Bio231/glycolysis.html http://highered.mcgraw-hill.com/sites/dl/free/007337797x/291136/glycolysis.swf Click here to view a different animation