The glucose molecule is oxidized (loses hydrogen atoms and electrons) during glycolysis, and each NAD+ molecule is reduced (gains a hydrogen atom and electrons) to NADH.

• Keep in mind that everytime one molecule is oxidized, another must be reduced.

Carbon-containing compounds are oxidized during cellular respiration, whereas the electron carriers NAD+ and FAD+ are reduced.

• In the early stages of glycolysis, two molecules of ATP are required.

• However, glycolysis produces four molecules of ATP, resulting in a net gain of two ATP molecules.

• The six-carbon glucose molecule is broken into two three-carbon pyruvate molecules at the end of glycolysis.

Glycolysis is a multistep process involving several enzyme-catalyzed stages and intermediates.

• Focus on where each step in cellular respiration happens and what the inputs and outputs are for each process when studying for the AP Biology test.

• The mitochondria are responsible for the next stage in cellular respiration.

• To enter the cell, the three-carbon pyruvate molecule must be changed.

Four molecules of ATP were produced as a result of substrate-level phosphorylation (two in glycolysis and two in the Krebs cycle).

• Twelve high-energy electron carriers (10 NADH and two FADH2) have been produced and will move on to the next stage of cellular respiration: oxidative phosphorylation.

• The electron transport chain (ETC) and chemiosmosis, which both occur on the inner membrane of the mitochondria, are both involved in oxidative phosphorylation.

• The vast majority of ATP generated in cellular respiration is produced by oxidative phosphorylation.

Electron carriers (NADH and FADH2) created during glycolysis, pyruvate oxidation, and the Krebs cycle carry electrons to the inner mitochondrial membrane's electron transport chain.

• The potential energy of electrons lowers as they pass along the electron transport chain, and energy is liberated.

• This energy is utilized to push protons (H+) out of the matrix and into the mitochondrial intermembrane space, resulting in a proton gradient.

• Proton concentrations in the intermembranous region can be 1,000 times higher than in the matrix!

Molecular oxygen (O2) interacts with four protons (H+) and four electrons (e–) at the end of the electron transport chain to generate two water molecules.

• As a result, during cellular respiration, oxygen serves as the ultimate, or terminal, electron acceptor.

• The electron transport chain's proton gradient is employed to drive ATP production.

• Chemiosmosis is the process of using a proton gradient to stimulate the synthesis of ATP.

• ATP is an enzyme.

Some membranes, for example, may be "leaky," allowing protons to enter the inner membrane of the mitochondria without passing through ATP synthase.

• As a result, the actual results from this technique may vary.

• NADH is oxidized (at the electron transport chain) to NAD+ during oxidative phosphorylation, which can subsequently be utilised in glycolysis.

However, oxidative phosphorylation cannot proceed in the absence of oxygen.

• (Recall that oxygen is the ETC's last electron acceptor.)

• Without oxygen, the ETC is unable to discharge its low-energy electrons from the final carrier, causing the chain to get clogged and the system to shut down.)

• Cells ferment under anaerobic environments to renew the NAD+ required to keep the glycolysis process going.

• If a cell ran out of NAD+, it would die.