Why is being reduced equivalent to having

Like the conversion of pyruvate to acetyl CoA, the citric acid cycle in eukaryotic cells takes place in the matrix of the mitochondria. Unlike glycolysis, the citric acid cycle is a closed loop: The last part of the pathway regenerates the compound used in the first step.

Part of this is considered an aerobic pathway oxygen-requiring because the NADH and FADH 2 produced must transfer their electrons to the next pathway in the system, which will use oxygen.

If oxygen is not present, this transfer does not occur. Two carbon atoms come into the citric acid cycle from each acetyl group. Two carbon dioxide molecules are released on each turn of the cycle; however, these do not contain the same carbon atoms contributed by the acetyl group on that turn of the pathway. The two acetyl-carbon atoms will eventually be released on later turns of the cycle; in this way, all six carbon atoms from the original glucose molecule will be eventually released as carbon dioxide.

It takes two turns of the cycle to process the equivalent of one glucose molecule. These high-energy carriers will connect with the last portion of aerobic respiration to produce ATP molecules.

One ATP or an equivalent is also made in each cycle. Several of the intermediate compounds in the citric acid cycle can be used in synthesizing non-essential amino acids; therefore, the cycle is both anabolic and catabolic. You have just read about two pathways in glucose catabolism—glycolysis and the citric acid cycle—that generate ATP. Most of the ATP generated during the aerobic catabolism of glucose, however, is not generated directly from these pathways.

Rather, it derives from a process that begins with passing electrons through a series of chemical reactions to a final electron acceptor, oxygen. These reactions take place in specialized protein complexes located in the inner membrane of the mitochondria of eukaryotic organisms and on the inner part of the cell membrane of prokaryotic organisms. The energy of the electrons is harvested and used to generate a electrochemical gradient across the inner mitochondrial membrane. The potential energy of this gradient is used to generate ATP.

The entirety of this process is called oxidative phosphorylation. The electron transport chain Figure 4. Oxygen continuously diffuses into plants for this purpose.

In animals, oxygen enters the body through the respiratory system. Electron transport is a series of chemical reactions that resembles a bucket brigade in that electrons are passed rapidly from one component to the next, to the endpoint of the chain where oxygen is the final electron acceptor and water is produced. There are four complexes composed of proteins, labeled I through IV in Figure 4. The electron transport chain is present in multiple copies in the inner mitochondrial membrane of eukaryotes and in the plasma membrane of prokaryotes.

In each transfer of an electron through the electron transport chain, the electron loses energy, but with some transfers, the energy is stored as potential energy by using it to pump hydrogen ions across the inner mitochondrial membrane into the intermembrane space, creating an electrochemical gradient.

Cyanide inhibits cytochrome c oxidase, a component of the electron transport chain. If cyanide poisoning occurs, would you expect the pH of the intermembrane space to increase or decrease? What affect would cyanide have on ATP synthesis? As they are passed from one complex to another there are a total of four , the electrons lose energy, and some of that energy is used to pump hydrogen ions from the mitochondrial matrix into the intermembrane space.

In the fourth protein complex, the electrons are accepted by oxygen, the terminal acceptor. The oxygen with its extra electrons then combines with two hydrogen ions, further enhancing the electrochemical gradient, to form water.

If there were no oxygen present in the mitochondrion, the electrons could not be removed from the system, and the entire electron transport chain would back up and stop. The mitochondria would be unable to generate new ATP in this way, and the cell would ultimately die from lack of energy. This is the reason we must breathe to draw in new oxygen. In the electron transport chain, the free energy from the series of reactions just described is used to pump hydrogen ions across the membrane.

Hydrogen ions diffuse through the inner membrane through an integral membrane protein called ATP synthase Figure 4. This complex protein acts as a tiny generator, turned by the force of the hydrogen ions diffusing through it, down their electrochemical gradient from the intermembrane space, where there are many mutually repelling hydrogen ions to the matrix, where there are few.

This flow of hydrogen ions across the membrane through ATP synthase is called chemiosmosis. Chemiosmosis Figure 4. Flashcards Collections. Documents Last activity. Add to Add to collection s Add to saved. Define the two catabolic pathways: a. Fermentation — a partial degradation of sugars that occurs without the use of oxygen b. Cellular respiration — when oxygen is consumed as a reactant along with the organic fuel; most efficient catabolic pathway; mitochondria house most of the metabolic equipment needed 2.

Use the following terms correctly in a sentence: redox reactions, oxidation, reduction, reducing agent and oxidizing agent. In redox reactions, oxidation the loss of electrons from one substance and reduction the addition of electrons to another substance occur. A reducing agent is the electron donor and the oxidizing agent is the electron acceptor. As electron loses potential energy when it shifts from a less electronegative atom toward a more electronegative one.

In cellular respiration, what is being oxidized and what is being reduced? Why are electron transport chains an advantage to living systems? What are the three stages of aerobic cellular respiration? Glycolysis, the citric acid cycle, oxidative phosphorylation: electron transport and chemiosmosis 8. What is substrate-level phosphorylation? Where is substrate level phosphorylation happening?

What is oxidative phosphorylation? What are cytochromes? It is an iron containing protein that transports electrons by accepting and donating electrons. The last cytochrome passes its electrons to oxygen Define chemiosmosis and label the diagram below. Label the diagram below of the activities occurring on the ECT. Complete the summary diagram of cellular respiration.

Page 5 of 7 Label the diagram of fermentation below: Does aerobic cellular respiration happen in prokaryotic organisms — if yes — where? What is the overall purpose of fermentation? Why does it have to occur?