Ch. 10 Chemotrophic Energy Metabolism

-flow of electrons, through or within membrane from reduced coenzymes to an electron acceptor, usually accompanied by ATP generation.

-Terminal electron acceptor is O₂, reduced form of acceptor is water -Occurs in Mitochondrion -Yields more energy than fermemtation-generate 36 or 38 ATP based on cell type

1. Glycolysis 2. Tricarboxylic acid (TCA/Krebs) cycle 3. Electron Transport 4. Oxidative Phosphorylation

Oxidizes incoming Carbon atoms into CO₂, conserves energy as reduced coenzyme molecules

A. transfer of e- from reduced coenzymes to O₂ b. coupled with active transport/pumping of protons across membrane- generate electrochemical protein gradient

Proton gradient driven O₂- dependent ATP synthesis

-in both chemotrophic & phototrophic org's -phototrophic org's also do aerobic respiration ex) In darkness, nonphotosyn. tissues -more mito. in cells w/intense metabolic activity ex) muscle contraction, flagella, cilia, sperm tails -1-few in protists, mammalian liver cells 500-1000/cell -interconnected network of nitochondria -in prokaryotes: respiratory fcts localized plasma membrane & cytoplasm

-phospholipid synthesis -fatty acid desaturation -fatty acid elongation

-Electron transport -Oxidative phosphorylation -Metabolite transport

-Pyruvate oxidation -TCA Cycle - (beta) oxidation of fats -DNA replication -RNA syn (transcription) -Protein syn (translation)

At TCA step 5 GTPis made in animal cells, ATP is generated in bacteria and plant mito-energetically equivalent Acetyl CoA + 3NAD+ + FAD + ADP + Pi -------> 2CO₂ + 3NADH + FADH₂ + CoA-SH+ATP

Glucose + 10NAD+ +2FAD + 4ADP + Pi -------> 6CO₂ + 10NADH + 2FADH₂ + 4ATP -Only >10% of energy generated in 4ATP (out of possible 36-38 ATP) -Free energy stored in NADH and FADH₂- high energy cmpds- use these to transfer electrons to drive synthesis of ATP

Allosteric reg of 4 key enzymes-reversible binding of effector molecules-to activate of inhibit enzyme catalytic activity. -TCA Cycle is highly sensitive to cell redox & energy status-assessed by NADH/NAD+ ratio & concentrations of ATP, ADP, AMP

-fat & protein catabolism -alternative fuel -fat-more energy/gram when oxidized than carbs -long-term energy storage -imp in hibernating animals, migrating birds, seed nutrient stores -max # calories w/min volume & weight -(beta)oxidation-removes 2-C units/time-generate acetyl CoA (goes into TCA Cycle)and NADH,FADH₂ -protein-not primary energy source-needed as enzymes, transport proteins, hormones, receptors, cell structure -When fasting/starvation of excess dietary protein-proteolysis by protease enzymes -Free amino acids-few intermediates in TCA Cycle

-catabolism -also source of precursors (4-6 Carbon) for anabolic pathways -Amphibolic pathway (both) -Precursors for protein syn, heme syn, citrate-fatty acid syn -Plants- oil bearing species-soybeans,peanuts, maize -Convert fat to sugar- use Beta oxidation & glyoxylate cycle