Pyruvate Oxidation or Oxidative Decarboxylation(if oxygen is present…)

The following occurs for each pyruvate:1. CO2 removed.2. NAD+ reduced to NADH and the 2-

carbon compound becomes acetic acid.3. Coenzyme A (CoA) attaches to acetic

acid to form acetyl-CoA.

Pyruvate Oxidation or Oxidative Decarboxylation

Pyruvate Oxidation or Oxidative Decarboxylation

Energy Yield & Products:2 NADH2 acetyl-CoA2 CO2 (released as waste)

Acetyl-CoAAcetyl-CoA CoA comes from vitamin BCoA comes from vitamin B55 Proteins, lipids, and carbohydrates are catabolized to Proteins, lipids, and carbohydrates are catabolized to

‘acetyl-CoA’‘acetyl-CoA’ It can be used to make fat or ATPIt can be used to make fat or ATP [ATP] determines what pathway this molecule takes[ATP] determines what pathway this molecule takes If OIf O22 is present, ‘acetyl CoA’ moves to the Kreb’s Cycle is present, ‘acetyl CoA’ moves to the Kreb’s Cycle

(aerobic respiration)(aerobic respiration) If OIf O22 is is NOTNOT present, ‘acetyl CoA’ becomes ‘lactate’ present, ‘acetyl CoA’ becomes ‘lactate’

(anaerobic respiration / fermentation)(anaerobic respiration / fermentation)

Krebs cycle - overview 8 step process, with each step catalyzed by 8 step process, with each step catalyzed by

a specific enzymea specific enzyme It is a ‘It is a ‘cyclecycle’ because ’ because oxaloacetateoxaloacetate is the is the

product of step 8, and the reactant in step 1product of step 8, and the reactant in step 1 REMEMBERREMEMBER: Two acetyl-CoA molecules : Two acetyl-CoA molecules

enter, so the Krebs Cycle must happen enter, so the Krebs Cycle must happen TWICETWICE for every one molecule of glucose for every one molecule of glucose that begins glycolysisthat begins glycolysis

The Krebs Cycle

Occurs twice for each molecule of glucose, 1 for each acetyl-CoA.

The Krebs Cycle – Key Features1. In step 1, acetyl-CoA combines with oxaloacetate to

form citrate.2. NAD+ is reduced to NADH in steps 3, 4 and 8.3. FAD is reduced to FADH2 in step 6.4. ATP if formed in step 5 by substrate-level

phosphorylation. The phosphate group from succinyl-CoA is transferred to GDP, forming GTP, which then forms ATP.

5. In step 8, oxaloacetate is formed from malate, which is used as a reactant in step 1.

6. CO2 is released in steps 3 and 4.

The Krebs CycleEnergy Yield & Products:2 ATP 6 NADH2 FADH2

4 CO2 (released as waste)

NADH and FADH2 carry electrons to the electron transport chain for further production of ATP by oxidative

phosphorylation.

Cellular Respiration so far has produced… GlycolysisGlycolysis

2 ATP 2 ATP (net)(net) 2 NADH, converted to 2 FADH2 NADH, converted to 2 FADH22

Pyruvate OxidationPyruvate Oxidation 2 NADH2 NADH

Krebs CycleKrebs Cycle 2 ATP2 ATP 6 NADH6 NADH 2 FADH2 FADH22

E.T.C. - Structure A series of electron acceptors (proteins) are

embedded in the inner mitochondrial membraneinner mitochondrial membrane. These proteins are arranged in order of increasing

electronegativity. The weakest attractor of electrons (NADH

dehydrogenase) is at the start of the chain and the strongest (cytochrome oxidase) is at the end.

Since the mitochondrial membrane is Since the mitochondrial membrane is highly highly foldedfolded, there are , there are multiplemultiple copies of the ETC copies of the ETC across the membraneacross the membrane

Electron Transport Chain - Overview NADH and FADHNADH and FADH22 transfer electrons to proteins transfer electrons to proteins

in the inner mitochondrial membranein the inner mitochondrial membrane The weakest electron attractors are at the start, The weakest electron attractors are at the start,

and the strongest are at the endand the strongest are at the end Each component is REDUCED, and then Each component is REDUCED, and then

subsequently OXIDIZEDsubsequently OXIDIZED Oxygen Oxygen (highly electronegative) (highly electronegative) oxidizes the last oxidizes the last

ETC componentETC component The energy released, moves HThe energy released, moves H++ atoms atoms (i.e. (i.e.

protons) protons) across mitochondrial membraneacross mitochondrial membrane

Electrochemical gradient is created, with a lot of H+ outside

Sets the rate of this process…

The energy stored in the [] gradient will be used in the second part of the ETC to power ATP synthesis