Energy Harvesting Pathways Glycolysis & Cellular Respiration

energy harvest, storage & transfers Figure 7.1

energy transfers two ways to transfer metabolic energy from one molecule to another –as free energy during coupled exergonic/ endergonic reactions –as “high energy” electrons during reduction/oxidation reactions

reduction reactions transfer energy Figure 7.2 of course, some usable energy is lost in the transfer

NAD + accepts reducing equivalents (H & e - ) Figure 7.4 (NADH+H + ) + 1/2 O 2 => NAD + + H 2 O  G = kcal·mol -1

NAD + /NADH shuttles reducing equivalents Figure 7.3

retrieving energy from storage glucose is the most common metabolic fuel –other fuel molecules use the same catabolic pathway when glucose is completely oxidized (burned) C 6      +6O 2 => 6CO 2 +6H 2 O + energy  G= -686 kcal/mol when glucose is oxidized metabolically C 6      +6O 2 => 6CO 2 +6H 2 O + energy ~ half of released energy is transferred to ATP

stages of glucose oxidation Figure 7.5

retrieving energy from storage glucose is oxidized by a series of regulated metabolic pathways –glycolysis (cytoplasmic) yields ATP, NADH & two 3C pyruvates –cellular respiration (mitochondrial) converts pyruvate to CO 2 & H 2 O, and yields ATP, and absolutely requires O 2

fermentation: partial oxidation of glucose in the absence of oxygen OR, if O 2 is short Figure 7.5

Cell Resp/Ferment Locations Table 7.1

free energy changes during glycolysis Figure 7.7

Investment, Isomerase, Harvest I, Harvest II Figure 7.6

glycolysis products: NADH (2) ATP (2) pyruvate (2) Figure 7.7

retrieving energy from storage glycolysis –a ten-step metabolic pathway –in the cytoplasm cellular respiration –NADH & pyruvate go to the mitochondrion pyruvate is oxidized, and decarboxylated –COOH functional group (carboxyl) is released as COO (CO 2 )

coenzyme A cycle Figure 7.8

citric acid cycle, tricarboxylic acid (TCA) cycle, Kreb’s cycle Figure 7.8

retrieving energy from storage pyruvate oxidation produces acetyl-CoA which enters the citric acid cycle 2C acetate joins 4C oxaloacetate => 6C citric acid atoms are rearranged CO 2 is released intermediates are oxidized ATP is formed more oxidation & rearrangement

final enzymatic disassembly of glucose by a cyclic acetate burner with energy capturing accessories Figure 7.8

energy yield of glycolysis and citric acid cycle Figure 7.9

retrieving energy from storage the major energy product of glycolysis and citric acid cycle is NADH the major metabolic energy demand is for ATP –citric acid cycle enzymes are in the mitochondrial matrix –NADH reduces an enzymatic pathway on the inner mitochondrial membrane

fate of electrons from glucose Figure 7.10

change in free energy during electron transport Figure 7.11

electron transport proton pump proton translocation during electron transport Figure 7.12

retrieving energy from storage NADH drives electron transport electron transport drives proton pumping proton pumping produces a transmembrane electrochemical gradient the phospholipid bilayer blocks diffusion of protons into the matrix

the ATP synthase proton channel relieves the transmembrane proton gradient, and the proton gradient drives ATP synthesis chemiosmosis Figure 7.12

a proton gradient is sufficient to generate ATP Figure 7.13

retrieving energy from storage fermentation –occurs when O 2 is insufficient to drive cellular (aerobic) respiration –IS NOT “anaerobic respiration” –regenerates NAD +

lactic acid fermentation regenerates NAD + Figure 7.14

ethanolic fermentation regenerates NAD + Figure 7.15

energy balance sheet Figure 7.16

interacting metabolic pathways Figure 7.17

transamination forms an amino acid Figure 7.18

positive & negative feedback coordinate the integrated metabolic pathways Figure 7.19

positive & negative feedback control glycolysis Figure 7.20