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Electron Carriers...
There are two electron carriers involved with cellular respiration; NAD and FAD
Form of the Mitochondria...
The structure of the mitochondrion is adapted to the function it performs.
CORRECTION : INTERMEMBRANE SPACE "PROTONS ARE PUMPED"
Function of Cellular Respiration...
Overview...
Glucose + Oxygen = Carbon Dioxide + Water + ATP
C6H12O6 + 6 O2 = 6 CO2 + 6 H2O + ATP
The last stage of cellular respiration produces the most ATP and is only possible because of the hydrogen concentration gradient, which, in return only exists due to the function of the ionic pumps powered by the electrons carried from the previous 3 stages.
1. Glycolysis...
Takes place in the cytoplasm, outside the mitochondria. Glucose is converted to pyruvate. The metabolic pathway in glycolysis is catalyzed by enzymes, which are found in the cytoplasm.
Glucose is partially oxidized and a small amount of ATP is produced; partial oxidization is achieved without the use of oxygen.
One glucose molecule is converted into two pyruvates. 2 ATP molecules are used but 4 are produced, so there is a net yield of 2 ATP molecules.
Two NAD+ are converted into two NADH + H+.
4 stages of Glycolysis;...
1.1 - Phosphorylation...
The addition of 2 phosphate groups to a molecule of glucose to form hexose biphosphate, to form an unstable molecule. Converts 2 ATP to ADP in the process.
1.2 - Lysis...
The hexose biphosphate splits to 2 triose phosphate due to it's unstable nature.
1.3 - Oxidation...
Two atoms of hydrogen are removed from each triose phosphate. The energy released by this oxidation is used to link another phosphate group, producing a three carbon compound carrying two phosphate groups. NAD is the hydrogen carrier that accepts the hydrogen atoms.
1.4 - ATP Formation...
Triose Biphosphate is converted to pyruvate, forming 2 ATP from ADP. As this is only half of the reaction it the output totals to 4 ATP.
2. The Link Reaction...
Pyruvate travels into the mitochondrial matrix from the cytoplasm.
The link reaction essentially prepares the pyruvate for the Krebs cycle.
Pyruvate than goes through oxidative decarboxylation, which is the combination of Decarboxylation and Oxidation, producing an acetyl group, which is accepted by an enzyme in the Krebs cycle.
The link reaction involves one decarboxylation and one oxidation. There are two more decarboxylation's and four more oxidations in the Krebs cycle.
3. The Krebs Cycle...
3 Stages of the Krebs Cycle;...
3.1 Decarboxylation...
Decarboxylation occurs in two of the reactions, it is a waste product and is excreted along with the CO2 from the link reaction.
3.2 Oxidation...
Oxidation occurs and hydrogen is removed in four of the reactions. In three of these reactions the hydrogen is accepted by NAD+ and in one reaction it is accepted by FAD.
The energy released by the oxidation reactions is stored in the electron carriers and used to make ATP at a later point.
3.3 Substrate-Level Phosphorylation...
One molecule of ATP is produced directly in one of these reactions. Phosphorylation occurs, however not powered by an enzyme, rather powered directly by an bond breaking.
4. The Electron Transport Chain...
Reduced NAD and FADH2 donate their electrons to electron carriers found in the inner membrane of the mitochondria. As the electrons are passed from carrier to carrier energy is utilized by proton pumps to transfer protons across the inner membrane from the matrix and into the inter-membrane space. The protons then flow through ATP Synthase down their concentration gradient providing the energy needed to make ATP.
The purpose of Oxygen...
Oxygen is needed to bind with the free protons exiting the electron transport chain to maintain the hydrogen gradient, resulting in the formation of water