Chapter 10: Chemotrophic Energy Metabolism: Aerobic Respiration

Cellular Respiration

Uses an external electron acceptor to oxidize substrates completely to CO2

Aerobic Respiration

The terminal electron acceptor is oxygen

Anaerobic Respiration

Other terminal electron acceptors are used(sulfur protons and ferric ions)

Mitochondria

Place where most aerobic ATP production in eukaryotic cells occurs

Where does aerobic respiration occur in prokaryotes?

Cytoplasm and Plasma Membrane

Aerobic Respiration Yields Much More Energy than Fermentation Does

Oxygen cotinuosly reoxidizes(recycles) coenzymes which allows them to turn over and keep glycolysis running

Respiration Stage 1

Glycolytic Pathway

Respiration Stage 2

Pyruvate is oxidized to produce Acetyl CoA

Respiration Stage 3

Acetyl Co A enters the citric acid cycle, where it is completely oxidized to CO₂

Respiration Stage 4

Electron transport, the transfer of electrons from reduced coenzymes to oxygen coupled to active transport of protons across a membrane

Respiration Stage 5

The electrochemical proton gradient formed in step 4 is used to drive ATP synthesis (oxidative phosphorylation)

Mitochondria is the site for all the reactions associated with the citric acid cycle, electron transport, and oxidative phosphorylation

True

Where are mitochondria typically clustered?

In regions of cells with the greatest need for ATP

Outer Membrane

Contains porins that allow passage of molecules with molar mass less than 5000 daltons

Intermembrane Space

The space between the inner and outer membranes and is continuos with the cytosol

Inner Membrane

Is impermeaable to most solutes and divides the mitochondria into the mitochondrial matrix and intermembrane space

Cristae

Infoldings of the inner membrane that increase its surface area to provide more space for electron transport.

Mitochondrial Matrix

Semifluid Interior of the mitochondria containing enzymes involved in mitochondrial function as well as DNA molecules and ribosomes

In what part of the Mitochondria do the Citric Acid Cycle, Pyruvate Oxidation, and catabolism of fatty acids and amino acids take place?

Mitochondrial Matrix

In what part of the Mitochondria does the electron transport chain occur?

Inner Membrane

In the presence of oxygen what happens to pyruvate?

Pyruvate is fully oxidized to carbon dioxide, and the released energy is used to drive ATP synthesis.

Citric Acid Cycle

Metabolizes Acetyl CoA produced from pyruvate decarboxylation. Acetyl CoA transfers its acetate group to a four-carbon acceptor called oxaloacetate, generating citrate.

The Fate of Citrate

After its formation, citrate undergoes two successive decarboxylations

It also goes through several oxidation steps

Eventually, oxaloacetate is regenerated and can accept two more carbons from acetyl CoA, and the cycle begins again

The Overall Cycle

Each round of the citric acid cycle involves:

the entry of two carbons

the release of two CO₂

and the regeneration of oxaloacetate

in each case, electrons are accepted by coenzymes

Pyruvate Dehydrogenase

Enzyme that converts Pyruvate to Acetyl CoA

Oxidative Decarboxylation

The removal of a carboxyl group from an organism while it is oxidized

CAC-1 Reactants

Water + Acetyl CoA + Oxaloacetate

CAC-1 Products

H⁺ + Citrate + CoA

Enzyme that Catalyzes CAC-1

Citrate Synthase

CAC-2 Reactants

Citrate

CAC-2 Products

Isocitrate

Enzyme that catalyzes CAC-2

Aconitase

CAC-3 Reactants

Isocitrate + NAD⁺

CAC-3 Products

CO₂ + Alpha-Ketogluterate + NADH

Enzyme that catalyzes CAC-3

Isocitrate Dehydrogenase

CAC-4 Reactants

Alpha-Ketogluterate + NAD⁺

CAC-4 Products

CO₂ + Succinyl CoA + NADH

Enzyme that catalyzes CAC-4

Alpha-Ketogluterate Dehydrogenase

CAC-5 Reactants

Succinyl CoA + GDP + Phosphate

CAC-5 Products

GTP + Succinate + CoA

Enzyme that Catalyzes CAC-5

Succinyl CoA synthetase

CAC-6 Reactants

Succinate + FAD

CAC-6 Proudcts

Fumarate + FADH₂

Enzyme that Catalyzes CAC-6

Succinate Dehydrogenase

CAC-7 Reactants

Fumarate + H2O

CAC-7 Products

Malate

Enzyme that catalyzes CAC-7

Fumarate Hydrates

CAC-8 Reactants

Malate + NAD⁺

CAC-8 Products

Oxaloacetate + NADH + H⁺

Enzyme that catalyzes CAC-8

Malate Dehydrogenase

What type of regulation does the CAC go through?

Allosteric Regulation of 4 key enzymes

Pyruvate Dehydrogenase Activators

CoA + NAD⁺+ AMP

Pyruvate Dehydrogenase Inhibitors

Acetyl CoA + NADH + ATP

Isocitrate Dehydrogenase Inhibitors

NADH

Isocitrate Dehydrogenase Activators

ADP

Alpha-Ketoglutarate Dehydrogenase Inhibitors

NADH + Succinyl CoA

Malate Dehydrogenase Inhibitors

NADH

How much ATP per glucose is yielded by the CAC?

4

Electron Transport

Coenzyme rexoidation by transfer of electrons to oxygen.

Electron Transport and ATP Generation are linked together

True

ATP Synthase

An integrak membrane protein that crams ADP and an inorganic phosphate to Make ATP

Oxidative Phosphorylation

Process where cells use energy produced by the oxidation of nutrients to yield ATP