Understanding the Electron Transport Chain - AP Biology

The major processes that occur in mitochondria are the citric acid cycle and the electron transport chain. The citric acid cycle forms electron carries that are used in the electron transport chain to reduce oxygen to water and produce ATP.

The final electron acceptor of the electron transport chain in cellular respiration is oxygen. Additionally carbon dioxide is produced as a waste product during the citric acid cycle phase of cellular respiration.

ATP Synthase work by converting the energy in the protons electrochemical gradient into production of ATP. This gradient is oriented across in the inner mitochondrial membrane so that protons is at a higher concentration in the intermembrane space than the matrix, and thus will flow from the intermembrane space to the matrix. This gradient is produced by the electron transport chain pumping protons from the matrix across the inner membrane to the intermembrane space.

During the reduction of oxygen to water, reactive oxygen species such as superoxide or hydrogen peroxide can be produced. These molecules are highly reactive and such can react with proteins or DNA to cause cellular damage or mutations.

The correct answer to this question is oxygen.

Oxygen is the final electron acceptor of electrons as they are passed down the electron chain. The electrons move and combine with oxygen to produce . Water and hydrogen are just byproducts of the acceptance of the electron, not the acceptor. The electrons are actually brought to the electron transport chain by carries like and .

In cellular respiration, oxygen is the final electron acceptor. Oxygen accepts the electrons after they have passed through the electron transport chain and ATPase, the enzyme responsible for creating high-energy ATP molecules. Just remember cellular **respiration—**respiration means breathing, and you cannot breathe without oxygen.

Oxygen is the final electron acceptor in the electron transport chain, showing the need for aerobic conditions to undergo such a process. ATP is produced as a product of the electron transport chain, while glucose and CO2 play a role in earlier processes of cellular respiration.

Glyceraldehyde-3-phosphate is converted to 1,3-bisphosphoglycerate, and one NADH is also produced during that step. NADH enters the electron transport chain, and is therefore worth ATP. Normally, an NADH is worth about 2.5 ATP; however, an NADH produced in glycolysis is only worth 1.5 ATP because it costs 1 ATP to move that NADH from the cytoplasm into the mitochondria. So, in this first step, we have a total of 1.5 ATP.

As the molecule continues on its path to become pyruvate, it will also produce two ATP directly; therefore, we have a net total of 3.5 potential ATP.

Cellular respiration typically follows three steps, under aerobic conditions. Glycolysis generates NADH and converts glucose to pyruvate, while producing small amounts of ATP through substrate-level phosphorylation. The citric acids cycle, or Krebs cycle, uses pyruvate to generate more NADH and FADH2. These NADH and FADH2 molecules donate electrons to the electron transport chain, which are used to pump protons into the intermembrane space of the mitochondrion. The protons in the intermembrane space then flow through ATP synthase to generate large amounts of ATP via oxidative phosphorylation.

Oxygen serves as the terminal electron acceptor for the electron transport chain. Electrons are donated by NADH molecules and passed through several different proteins to generate the proton gradient in the intermembrane space. Upon reaching the final protein, the electron is bonded to an oxygen molecule to create water. Without oxygen, there would be nowhere for the electrons to go after being pumped through the electron transport chain, and aerobic cellular respiration would be impossible.

Oxygen is the final electron acceptor in the electron transport chain, which allows for oxidative phosphorylation. Without oxygen, the electrons will be backed up, eventually causing the electron transport chain to halt. This will cause the products of glycolysis to go through fermentation instead of going to the citric acid cycle. Without oxygen, oxidative phosphorylation (the electron transport chain) is impossible, but substrate-level phosphorylation (glycolysis) continues.

Cellular respiration is only about 38% efficient, with the rest of the energy in glucose lost as heat.

Water and carbon dioxide are not used to store energy. Fats can be synthesized from acetyl CoA and glycerol, but are not generally created in large quantities during cellular respiration. Starches are generally used for energy storage in plants, but can be synthesized from glucose; however, starches are not a standard product of cellular respiration.

Most of the reactions in cellular respiration are exothermic, in order to support spontaneous reaction. The result is release of heat energy with most steps.

Oxygen acts as the terminal electron acceptor in the electron transport chain (ETC). This accounts for the reason as to why, when cells are starved of oxygen, the ETC "backs up" and the cell will divert to using anaerobic respiration, such as fermentation. At the end of the electron transport chain, the electron and a proton are passed to an oxygen molecule to produce water.

The citric acid cycle depends on oxygen in an indirect sense. The main purpose of the cycle is to produce electron donors for the electron transport chain. If the chain is not functional (due to lack of oxygen), the citric acid cycle also stops functioning. Glycolysis is not dependent on oxygen, and can function in anaerobic environments.

In ATP synthesis, the proton gradient is an interconvertible form of energy in electron transport. 2,4-dinitrophenol is an inhibitor of ATP production in cells with mitochondria. Its mechanism of action involves carrying protons across the mitochondrial membrane, which leads to the consumption of energy without ATP production.

The other answer choices are not directly related to the generation of the proton gradient.

The events of the electron transport chain take place on the inner membrane of the mitochondria. The transmembrane proteins used to shuttle electrons through the electron transport chain are embedded on the inner membrane. Electrons are donated to these proteins and used to transfer protons into the intermembrane space from the matrix. After reaching the final inner membrane protein in the chain, the electron is transferred to oxygen to form water.

The mitochondrial matrix is where the ATP eventually is eventually synthesized, as well as the site of the citric acid cycle. The cytoplasm is the site of glycolysis. The outer mitochondrial membrane is not directly involved in cellular respiration.

NADH and FADH2 are electron carriers that have the important function of actually bringing electrons to the electron transport chain. Proteins embedded in the inner membrane of the mitochondria oxidize these molecules. The proteins then transfer the electrons through a series of processes in order to pump protons into the intermembrane space, creating an electrochemical gradient. The final protein in the chain passes the electron to an oxygen molecule to generate water, and the protons in the intermembrane space can then be used to drive the function of ATP synthase to create ATP/

NADH and FADH2 are not directly involved in ATP synthesis and oxygen is the ultimate electron acceptor in the electron transport chain.

Glucose is the primary molecule that heterotrophs use to make energy at a cellular level. Heterotrophs use glucose for a starting material in both fermentation and cellular respiration. However fermentation is performed without oxygen (anaerobic), while cellular respiration requires oxygen as a final electron receptor at the end of the electron transport chain.

The direct purpose of moving electrons down the electron transport chain is to pump protons (hydrogen ions) into the intermembrane space. This creates a chemiosmotic gradient that the cell uses to generate ATP by selectively allowing hydrogen ions to move back into the mitochondrial matrix.

Energy is not directly captured as electrons travel down the electron transport chain to synthesize ATP. GTP is a product of the Krebs cycle and can be used to generate cellular energy, but is not involved in synthesizing ATP or the electron transport chain. Other metabolic processes are often used to regulate glucose concentrations in the blood, indirectly influencing the rate of glycolysis and cellular respiration, but these processes do not directly provide energy for the electron transport chain.

Electrons from electron carriers, such as NADH and FADH2, go through the electron transport chain, which involves a series of molecules that accept and donate electrons. Transfer to the electron through these proteins results in the net movement of protons across the inner mitochondrial membrane and into the intermembrane space, generating the proton gradient that will drive ATP synthase.

The final molecule in the electron transport chain is oxygen. The oxygen molecule accepts the electron from the final protein in the chain and becomes water, one of the final products of metabolism. Remember that each subsequent molecule in the electron transport chain has a higher affinity for electrons than the molecule before it; therefore, the final electron acceptor will have the highest affinity for electrons. Oxygen has a very high electronegativity, making it a good electron acceptor.