The Krebs cycle creates a proton gradient between the intermembrane space and the inner mitochondrial membrane. This proton gradient provides the energy necessary to drive the proton through the ATP synthase. As the protons are passively diffusing through the ATP synthase, the energy is coupled to phosphorylate ADP to ATP. If a base were injected into this space, then it would would consume these protons due to its electronegativity and decrease ATP synthase’s ability to transform ADP to 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 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.

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.

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.

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 .

The final electron acceptor in the electron transport chain is oxygen. It gets reduced by accepting two electrons and two protons from the ATP synthase to form water via the following equation:

A total of 38 ATP molecules are produced from one molecule of glucose. 2 ATP from glycolysis, 2 ATP from the Krebs cycle, and about 34 ATP from the electron transport chain. Note that this is a theoretical maximum and is rarely seen in nature.

Oxidative phosphorylation is composed of electron transport and chemiosmosis. Chemiosmosis occurs when ions cross a selectively permeable membrane down their concentration gradient. In cellular respiration, hydrogen ions (protons) move down their concentration gradient through a membrane protein to produce ATP. The gradient of protons is established by the electron transport portion of oxidative phosphorylation, which is used to transfer protons into the intermembrane space. Protein complexes I, II, III, and IV help protons to cross the membrane.

Substrate-level phosphorylation occurs during glycolysis, and does not utilize chemiosmosis.

are the two electron carriers in the Krebs cycle. ATP is the energy compound that is created in respiration. Carbon dioxide is a waste product from the Krebs cycle. Nitrogen is not involved in the Krebs cycle. Oxygen is an electron acceptor, and hydrogen is added to the electron carriers.