Harvesting Energy from Organic Molecules

Harvesting Energy from Organic Molecules
Cellular Respiration Harvesting Energy from Organic Molecules

Oxidative phosphorylation: electron transport and chemiosmosis
Overview Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Cytosol

Energy investment phase
GLYCOLYSIS Glycolysis Citric acid cycle Oxidative phosphorylation ATP 2 ATP 4 ATP used formed Glucose 2 ATP + 2 P 4 ADP + 4 2 NAD+ + 4 e- + 4 H + 2 NADH + 2 H+ 2 Pyruvate + 2 H2O Energy investment phase Energy payoff phase 4 ATP formed – 2 ATP used 2 NAD+ + 4 e– + 4 H + Figure 9.8 Energy-requiring phase (4 steps) Energy-producing phase (5 steps) PGAL

Phosphoglucoisomerase
GLYCOLYSIS (1st part) Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H OH HO CH2OH O P CH2O CH2 C CHOH ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase Glycolysis 1 2 3 4 5 Oxidative phosphorylation Citric acid cycle Figure 9.9 A Phosphorylation of Glucose into Glucose-6-phosphate Hexokinase. Secures glucose in the cell Makes glucose more reactive.

GLYCOLYSIS (1st part) Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H OH HO CH2OH O P CH2O CH2 C CHOH ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase Glycolysis 1 2 3 4 5 Oxidative phosphorylation Citric acid cycle Figure 9.9 A 2. Glucose-6-phosphate is rearranged into Fructose-6-phosphate (an isomer). Phosphoglucoisomerase

GLYCOLYSIS (1st part) Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H OH HO CH2OH O P CH2O CH2 C CHOH ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase Glycolysis 1 2 3 4 5 Oxidative phosphorylation Citric acid cycle Figure 9.9 A 3. Phosphorylation of Fructose-6-phosphate into Fructose-1,6-bisphosphate Phosphofructokinase Makes glucose even more reactive. Enzyme is allosterically controlled by ATP & ADP.

GLYCOLYSIS (1st part) Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H OH HO CH2OH O P CH2O CH2 C CHOH ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase Glycolysis 1 2 3 4 5 Oxidative phosphorylation Citric acid cycle Figure 9.9 A 4. Fructose-1,6-bisphosphate is split into Dihydroxyacetone phosphate + Glyceraldehyde-3-phosphate Aldolase Splits the 6-carbon glucose into two 3-carbon molecules Isomerase converts extra Dihydroxyacetone phosphate into G3P (PGAL). (Also known as PGAL)

1, 3-Bisphosphoglycerate
GLYCOLYSIS (2nd part) 2 NAD+ NADH 2 + 2 H+ Triose phosphate dehydrogenase P i P C CHOH O CH2 O– 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase 3-Phosphoglycerate Phosphoglyceromutase CH2OH H 2-Phosphoglycerate 2 H2O Enolase Phosphoenolpyruvate Pyruvate kinase CH3 6 8 7 9 10 Pyruvate Figure 9.8 B Glyceraldehyde-3-phosphate is converted into 1,3-Bisphosphoglycerate Triose phosphate dehydrogenase Oxidation of G3P (PGAL) Electrons removed and transferred to NAD+, forming NADH An additional phosphate group is added

GLYCOLYSIS (2nd part) 2 NAD+ NADH 2 + 2 H+ Triose phosphate dehydrogenase P i P C CHOH O CH2 O– 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase 3-Phosphoglycerate Phosphoglyceromutase CH2OH H 2-Phosphoglycerate 2 H2O Enolase Phosphoenolpyruvate Pyruvate kinase CH3 6 8 7 9 10 Pyruvate Figure 9.8 B 2. 1,3-Bisphosphoglycerate “unwinds” into 3-Phosphoglycerate Phosphoglycerokinase Phosphate is moved to ADP, creating ATP Substrate-level phosphorylation

GLYCOLYSIS (2nd part) 2 NAD+ NADH 2 + 2 H+ Triose phosphate dehydrogenase P i P C CHOH O CH2 O– 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase 3-Phosphoglycerate Phosphoglyceromutase CH2OH H 2-Phosphoglycerate 2 H2O Enolase Phosphoenolpyruvate Pyruvate kinase CH3 6 8 7 9 10 Pyruvate Figure 9.8 B 3-Phosphoglycerate is rearranged into 2-Phosphoglycerate Phosphoglyceromutase Phosphate group is moved to a different carbon

GLYCOLYSIS (2nd part) 2 NAD+ NADH 2 + 2 H+ Triose phosphate dehydrogenase P i P C CHOH O CH2 O– 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase 3-Phosphoglycerate Phosphoglyceromutase CH2OH H 2-Phosphoglycerate 2 H2O Enolase Phosphoenolpyruvate Pyruvate kinase CH3 6 8 7 9 10 Pyruvate Figure 9.8 B 4. 2-Phosphoglycerate is converted into Phosphoenolpyruvate (PEP) Enolase A double bond is formed Water is produced The phosphate group becomes very unstable

GLYCOLYSIS (2nd part) 2 NAD+ NADH 2 + 2 H+ Triose phosphate dehydrogenase P i P C CHOH O CH2 O– 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase 3-Phosphoglycerate Phosphoglyceromutase CH2OH H 2-Phosphoglycerate 2 H2O Enolase Phosphoenolpyruvate Pyruvate kinase CH3 6 8 7 9 10 Pyruvate Figure 9.8 B 5. ADP is again phosphorylated through the conversion of Phosphoenolpyruvate (PEP) into Pyruvate Pyruvate kinase Phosphate is moved to ADP, creating ATP Substrate-level phosphorylation

GLYCOLYSIS Available

Back to our Overview… Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Cytosol

KREBS CYCLE (Citric Acid Cycle)
9 steps. Further oxidation of the sugar fragments (pyruvate) Occurs in the MITOCHONDRION, specifically, in the Matrix (fluid portion).

Oxidative phosphorylation
KREBS CYCLE OVERVIEW ATP 2 CO2 3 NAD+ 3 NADH + 3 H+ ADP + P i FAD FADH2 Citric acid cycle CoA Acetyl CoA NADH CO2 Pyruvate (from glycolysis, 2 molecules per glucose) Glycolysis Oxidative phosphorylation Figure 9.11

Pyruvate is conveted into Acetyl coenzyme A (by multiple enzymes) Pyruvate is converted into Acetate when a carboxyl group is removed, yeilding CO2 Acetate is oxidized, its electron transferred to NAD+, forming NADH Coenzyme A is added, making Acetate very reactive CYTOSOL MITOCHONDRION NADH + H+ NAD+ 2 3 1 CO2 Coenzyme A Pyruvate Acetyl CoA S CoA C CH3 O Transport protein O– Figure 9.10

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 2. Acetyl CoA attaches its Acetate to Oxaloacetate (OAA), forming Citrate. Forms a 6-carbon molecule, a “pseudo-glucose”

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 3. Citrate is converted to its isomer, Isocitrate. Water is removed, then re-attached.

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 4. Carbon is lost from Isocitrate (as CO2), and the 5-carbon product is then oxidized into α-Ketoglutarate. An electron is transferred to NAD+, forming NADH.

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 5. Carbon is lost from α-Ketoglutarate (as CO2), and the 4-carbon product is then oxidized into Succinate, to which coenzyme A is added, forming Succinyl CoA. An electron is transferred to NAD+, forming NADH.

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 6. Succinyl CoA is phosphorylated (displacing coenzyme A and forming Succinate) The phosphate is transferred to GDP to form GTP, which then transfers the phosphate to ADP, forming ATP. Substrate-level Phosphorylation

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 7. Succinate is oxidized, forming Fumarate. An electron is transferred to FAD, forming FADH2 (which subsequently passes the e- to ubiquinone, forming ubiquinol)

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 8. Fumarate is rearranged into Malate with the addition of water.

Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA a-Ketoglutarate Isocitrate Citric acid cycle S SH FADH2 FAD GTP GDP NAD+ ADP P i CO2 H2O + H+ C CH3 O COO– CH2 HO HC CH 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation ATP Figure 9.12 9. Malate is oxidized, forming Oxaloacetate (OAA). An electron is transferred to NAD+, forming NADH. OAA is re-formed – important!

Out Available Electrons to the cristae!

Back to our Overview… Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Cytosol

ELECTRON TRANSPORT SYSTEM
10-11 steps. Chemiosmotic Phosphorylation = mass production of ATP. Occurs in the MITOCHONDRION, specifically, on the Cristae (membrane portion).

ELECTRON TRANSPORT SYSTEM
Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP Inner Mitochondrial membrane H+ P i Protein complex of electron carners Cyt c I II III IV (Carrying electrons from, food) NADH+ FADH2 NAD+ FAD+ 2 H+ + 1/2 O2 H2O ADP + Electron transport chain Electron transport and pumping of protons (H+), which create an H+ gradient across the membrane Chemiosmosis ATP synthesis powered by the flow Of H+ back across the membrane synthase Q Oxidative phosphorylation Intermembrane space mitochondrial matrix Figure 9.15

Overview

What if there’s no oxygen?
Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis Oxidative Mitochondrion Cytosol Something OTHER THAN O2 is the final electron acceptor… Lactate Fermentation Pyruvate accepts the electrons. Animals, some Protists Alcohol Fermentation Acetaldehyde accepts the electrons. Plants, some Protists, some Fungi

Lactate Fermentation

Ethanol Fermentation

Harvesting Energy from Organic Molecules

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