Metabolic Processes 2:Metabolic Processes 2:

Aerobic RespirationAerobic Respiration

Aerobic RespirationAerobic Respiration Basically refers to the catabolic (breaking down)

pathways that require oxygen. Summary reaction:

Substrate level phosphorylation: when a phosphate group is transferred onto an ADP molecule to create ATP

Basically refers to the catabolic (breaking down) pathways that require oxygen.

Summary reaction:

Substrate level phosphorylation: when a phosphate group is transferred onto an ADP molecule to create ATP

GlycolysisGlycolysis Glycolysis is the first step in Aerobic Respiration. Basically, you will break the glucose (starting sugar) from

a 6-carbon molecule into two separate 3-carbon molecules called pyruvates

You get two net ATP molecules out of this You also get two NADH molecules (NAD+ is reduced to

NADH…. We will see what happens to them later…) Net reaction: Glucose + 2NAD+ + 2ADP + 2Pi --> 2pyruvate + 2H2O +

2NADH + 2ATP

Glycolysis is the first step in Aerobic Respiration. Basically, you will break the glucose (starting sugar) from

a 6-carbon molecule into two separate 3-carbon molecules called pyruvates

You get two net ATP molecules out of this You also get two NADH molecules (NAD+ is reduced to

NADH…. We will see what happens to them later…) Net reaction: Glucose + 2NAD+ + 2ADP + 2Pi --> 2pyruvate + 2H2O +

2NADH + 2ATP

Glycolysis Glycolysis

Glycolysis in a bunch of chemical words…Glycolysis in a bunch of chemical words… Glucose + ATP = Glucose-6-phosphate which changes into

isomer fructose-6-phosphate Fructose-6-phosphate + ATP = fructose 1, 6-biphosphate which

then splits into 2 glyceraldehyde 3-phosphate molecules A hydrogen comes off and reduces NAD+ to NADH for each

molecule at the same time an inorganic phosphate is added to each to create 2 molecules of 1,3-biphosphoglycerate.

One phosphate comes off each molecule and forms a total of 2 ATPs and two 3-phosphoglycerate molecules, which then change into two 2-phosphoglycerate.

Each of the 2-phosphoglycerate molecules lose a water molecule and become phosphoenolpyruvates

Each phosphoenolpyruvate loses a phosphate to form an ATP and pyruvate.

Glucose + ATP = Glucose-6-phosphate which changes into isomer fructose-6-phosphate

Fructose-6-phosphate + ATP = fructose 1, 6-biphosphate which then splits into 2 glyceraldehyde 3-phosphate molecules

A hydrogen comes off and reduces NAD+ to NADH for each molecule at the same time an inorganic phosphate is added to each to create 2 molecules of 1,3-biphosphoglycerate.

One phosphate comes off each molecule and forms a total of 2 ATPs and two 3-phosphoglycerate molecules, which then change into two 2-phosphoglycerate.

Each of the 2-phosphoglycerate molecules lose a water molecule and become phosphoenolpyruvates

Each phosphoenolpyruvate loses a phosphate to form an ATP and pyruvate.

Pyruvate OxidationPyruvate Oxidation After the glucose is split into two pyruvate molecules in

the cytoplasm, they must travel into the mitochondrial matrix.

One of the three carbons is cleaved off and released as CO2

The remaining molecule (acetyl) then combines with a coenzyme called coenzyme A (acetyl coA for short) and at the same time another NAD+ is reduced to NADH.

Because one glucose molecule makes 2 pyruvates, this happens twice, creating 2 acetyl coA molecules and 2 NADH.

After the glucose is split into two pyruvate molecules in the cytoplasm, they must travel into the mitochondrial matrix.

One of the three carbons is cleaved off and released as CO2

The remaining molecule (acetyl) then combines with a coenzyme called coenzyme A (acetyl coA for short) and at the same time another NAD+ is reduced to NADH.

Because one glucose molecule makes 2 pyruvates, this happens twice, creating 2 acetyl coA molecules and 2 NADH.

Pyruvate OxidationPyruvate Oxidation

The Krebs CycleThe Krebs Cycle Both acetyl coA molecules will go through a

Krebs cycle. Each acetyl group has 2 carbons left that will

be released as CO2 A series of reactions occur for each acetyl coA

that enters the cycle and you get 3NADHs, 2 CO2s, 1 ATP, 1FADH2 and you have to put in 1H2O molecule.

Remember: this happens for each acetyl coA, so twice per glucose molecule.

Both acetyl coA molecules will go through a Krebs cycle.

Each acetyl group has 2 carbons left that will be released as CO2

A series of reactions occur for each acetyl coA that enters the cycle and you get 3NADHs, 2 CO2s, 1 ATP, 1FADH2 and you have to put in 1H2O molecule.

Remember: this happens for each acetyl coA, so twice per glucose molecule.

The Krebs CycleThe Krebs Cycle

The Krebs Cycle in Chemical Words…The Krebs Cycle in Chemical Words… Oxaloacetate (4C) is the starting and ending point of the cycle. Oxaloacetate combines with acetyl-CoA to form citrate (6C) and the co-

enzyme A comes off. Citrate changes into isocitrate (6C) Isocitrate loses a CO2 and a Hydrogen (to NAD+) to form alpha-

ketoglutarate (5C) Alpha-ketoglutarate loses a CO2 as well and againa hydrogen is lost to

NAD+ at the same time another co-A is added to form succinyl-CoA (4C) Co-A comes off again, giving energy for a GDP to form GTP, then ADP to

form ATP. What is left is a succinate molecule (4C) Succinate loses another hydrogen, but this time to FAD+ to form FADH2

and fumerate (4C) Water is added to fumerate to make malate (4C) Malate loses a hydrogen to NAH+ and forms oxaloacetate (4C). The

process happens again for the next acetyl Co-A.

Oxaloacetate (4C) is the starting and ending point of the cycle. Oxaloacetate combines with acetyl-CoA to form citrate (6C) and the co-

enzyme A comes off. Citrate changes into isocitrate (6C) Isocitrate loses a CO2 and a Hydrogen (to NAD+) to form alpha-

ketoglutarate (5C) Alpha-ketoglutarate loses a CO2 as well and againa hydrogen is lost to

NAD+ at the same time another co-A is added to form succinyl-CoA (4C) Co-A comes off again, giving energy for a GDP to form GTP, then ADP to

form ATP. What is left is a succinate molecule (4C) Succinate loses another hydrogen, but this time to FAD+ to form FADH2

and fumerate (4C) Water is added to fumerate to make malate (4C) Malate loses a hydrogen to NAH+ and forms oxaloacetate (4C). The

process happens again for the next acetyl Co-A.

Oxidative PhosphorylationOxidative Phosphorylation This is where the NADH and FADH2 come to be oxidized while

ATP is being made from ADP. Uses an electron transport chain (ETC) which is a series of

proteins and electron carriers that are embedded in the inner membrane of the mitochondrion.

It is where most of the ATP is made from the original glucose molecule.

The NADH and FADH2 drop off their H’s in the matrix. H+’s go through the membrane into the intermembrane space and the electrons travel through the chain.

Here is where we use oxygen as the final electron acceptor and is converted to water.

Note: NADH pushes 3 H+s through but FADH2 only pushes 2 H+s through

This is where the NADH and FADH2 come to be oxidized while ATP is being made from ADP.

Uses an electron transport chain (ETC) which is a series of proteins and electron carriers that are embedded in the inner membrane of the mitochondrion.

It is where most of the ATP is made from the original glucose molecule.

The NADH and FADH2 drop off their H’s in the matrix. H+’s go through the membrane into the intermembrane space and the electrons travel through the chain.

Here is where we use oxygen as the final electron acceptor and is converted to water.

Note: NADH pushes 3 H+s through but FADH2 only pushes 2 H+s through

Oxidative PhosphorylationOxidative Phosphorylation

ChemiosmosisChemiosmosis

The energy from the reduced NADH and FADH2 is used to establish an electrochemical gradient (hydrogen ion gradient)

inside the intermembrane space is a high concentration of hydrogen ions

The hydrogen ions then pass through the ATP synthase complexes which phosphorylate ADP to form ATP.

The energy from the reduced NADH and FADH2 is used to establish an electrochemical gradient (hydrogen ion gradient)

inside the intermembrane space is a high concentration of hydrogen ions

The hydrogen ions then pass through the ATP synthase complexes which phosphorylate ADP to form ATP.

ChemiosmosisChemiosmosis

Yield of ATP from Aerobic Respiration

Yield of ATP from Aerobic Respiration

Prokaryotes can generate as much as 38 ATP molecules from glucose

Eukaryotes can generate as much as 36 ATP (2 ATPs are expended getting the NADH from glycolysis across the mitochondrial membrane)

Experimental observations show that the actual number is lower possibly because Some protons leak through the membrane and don’t go through the

ATP synthase Some energy goes to transporting pyruvate molecules across the

mitochondrial membrane Some energy goes into transporting the ATP molecules made into the

cytoplasm.

Prokaryotes can generate as much as 38 ATP molecules from glucose

Eukaryotes can generate as much as 36 ATP (2 ATPs are expended getting the NADH from glycolysis across the mitochondrial membrane)

Experimental observations show that the actual number is lower possibly because Some protons leak through the membrane and don’t go through the

ATP synthase Some energy goes to transporting pyruvate molecules across the

mitochondrial membrane Some energy goes into transporting the ATP molecules made into the

cytoplasm.