CELLULAR RESPIRATION and FERMENTATION

Energy Harvest Fermentation – partial breakdown w/o oxygen Cellular Respiration – most efficient, oxygen consumed, mitochondria Cells recycle ATP Redox reactions (oil/rig); reducing agent – electron donor; oxidizing agent – acceptor Cell Resp: glucose oxidized – H removed; oxygen reduced – accepts H

ATP – adenosine triphosphate

ATP CYCLE ATP + H 2 0 ↔ ADP + P i + energy

Energy flow and chemical recycling in ecosystems

NAD + electron shuttle Nicotinamide adenine dinucleotide Coenzyme, oxidizing agent, reduced form NADH NADH shuttles electrons to ETC

ETC – proteins, cytochromes in cristae, series of smaller steps, stores released energy to make ATP, oxygen combines w/ electrons and proton

Glycolysis glucose  pyruvate; cytosol

Krebs cycle mitochondrial matrix, pyruvate  acetyl CoA & CO 2

PHOSPHORYLATION OXIDATIVE –ATP synthesis powered by redox reactions –Electron transport chain –Requires oxygen (final electron acceptor) SUBSTRATE LEVEL –ATP synthesis from transfer of phosphate group from substrate to ADP –Glycolysis and Krebs cycle

Substrate level Phosphorylation in glycolysis

GLYCOLYSIS Splitting of glucose C 6 H 12 O 6 → 2 C 3 H 3 O 3 Uses 2 ATP’s Makes 4 ATP’s Net 2 ATP’s 2 NADH & 2 H + ← SUMMARY

GLYCOLYSIS Glucose → 2G3P → 2 PGA → 2 pyruvates ↑ ↑ ↑ requires 2 NAD + generates 2 ATP’s reduced 4 ATP’s 2 NADH

Oxidation of Pyruvate Occurs in mitochondrion, requires transport protein & coenzyme A Yields Acetyl CoA, 1 NADH & 1 H + from each pyruvate (2 total) Waste – carbon dioxide

KREBS CYCLE Occurs in mitochondrial matrix 1 cycle/pyruvate 2 cycles/glucose Acetyl CoA (2-C) + oxaloacetate (4-C) → citrate (6-C) 7 more steps: 2CO 2 removed, 3NADH & H +, 1FADH 2 1 ATP – substrate phosphorylation

Oxaloacetate 4-C Citrate 6-C

ELECTRON TRANSPORT Cristae of mitochondrion – foldings ↑ surface area Electron carriers (proteins) embedded in membrane NADH “delivers” electrons to first molecule in chain (3 ATP’s); FADH 2 adds electrons at lower level (2 ATP’s) Last cytochrome passes electrons to ½O 2 + H 2 → H 2 O

CHEMIOSMOSIS Energy coupling ATP synthase  Generates ATP  Molecular mill  Powered by proton flow Uses exergonic flow of electrons to pump H + (protons) from matrix into intermembrane space, they flow back through ATP synthase H + gradient couples redox reactions of ETC to ATP synthesis

SUMMARY

FERMENTATION Anaerobic glycolysis followed by break down of pyruvates Substrate level phosphorylation Regenerates NAD + from NADH Alcoholic: yeast, bacteria, produces – 2 ATP, 2 CO 2 & 2 ethanol from pyruvates Lactic acid: fungi, human muscle cells, bacteria, produces – 2 ATP & 2 lactates from pyruvate Acetic acid: bacteria, 2 ATP, 2 CO 2 & 2 acetic acids from pyruvates

Fermentation vs Respiration Both oxidize glucose in glycolysis Pyruvate & 2 ATP’s NAD + accepts electrons Key difference: Oxidation of NADH (NAD + required to sustain glycolysis) Final e- acceptor (organic molecule vs O 2 ) 2 ATP’s vs 38 ATP’s

Facultative anaerobes Yeast Bacteria Human muscle cells Evolutionary significance of glycolysis?

Other metabolic pathways Versatility of catabolism Biosynthesis Anabolic pathways may use intermediates & consume ATP

FEEDBACK MECHANISMS CONTROL CELLULAR RESPIRATION