Respiração Celular (Parte 3) - Cadeia Respiratória | Biologia com Samuel Cunha

Summary

This video explains the intricate process of cellular respiration, focusing on the electron transport chain (ETC) in mitochondria. It details how NADH and FADH2 contribute high-energy electrons, which drive the pumping of protons (H+) across the mitochondrial membrane, creating a gradient that powers ATP synthesis through ATP synthase. Oxygen serves as the final electron acceptor, forming water. The ETC generates 34 ATP per glucose molecule, with slight variations in specific cell types. The process is crucial for energy production in cells, and the video highlights how oxygen plays a key role in sustaining life through cellular respiration.

Takeaways

• 😀 The respiratory chain, or electron transport chain, is the final stage of cellular respiration where most ATP is produced.
• 😀 During cellular respiration, the glycolysis and Krebs cycle produce 4 ATP, 10 NADH, and 2 FADH2, which enter the electron transport chain.
• 😀 The electron transport chain occurs in the inner membrane of the mitochondria, particularly within the cristae.
• 😀 NADH and FADH2 donate high-energy electrons that travel through membrane proteins, releasing energy to pump protons (H+) across the mitochondrial membrane.
• 😀 The protons accumulate in the intermembrane space, creating a proton gradient, which drives ATP production via ATP synthase.
• 😀 NADH produces 3 ATP molecules per molecule, while FADH2 produces 2 ATP molecules due to fewer protons being pumped.
• 😀 A total of 34 ATP molecules are produced by the electron transport chain, in addition to 4 ATP from glycolysis and the Krebs cycle, for a total of 38 ATP per glucose molecule.
• 😀 However, in some cells, like muscle cells or neurons, only 36 ATP are produced due to a small energy cost for transporting NADH into the mitochondria.
• 😀 Oxygen is crucial in cellular respiration as the final electron acceptor in the electron transport chain, forming water by combining with electrons and protons.
• 😀 The electron transport chain is essential for creating the energy (ATP) needed for cellular functions, and it also generates heat as a byproduct, which is why we feel warm during exercise.

Q & A

What is the Electron Transport Chain (ETC) in cellular respiration?

The Electron Transport Chain (ETC) is the third step of cellular respiration, occurring in the inner mitochondrial membrane. It involves the transfer of electrons from NADH and FADH2 through a series of proteins, ultimately producing ATP and water.

How do NADH and FADH2 contribute to the Electron Transport Chain?

NADH and FADH2 release high-energy electrons into the Electron Transport Chain. These electrons pass through proteins in the inner mitochondrial membrane, releasing energy that is used to pump protons (H+) across the membrane, creating a proton gradient.

What role does oxygen play in the Electron Transport Chain?

Oxygen acts as the final electron acceptor in the Electron Transport Chain. It combines with the electrons and protons (H+) to form water, completing the process of electron transport and preventing the chain from backing up.

How does the proton gradient contribute to ATP production?

The proton gradient created by the Electron Transport Chain drives the production of ATP. Protons flow back into the mitochondrial matrix through the ATP synthase enzyme, which uses this energy to synthesize ATP from ADP and inorganic phosphate.

Why do NADH molecules produce 3 ATP, but FADH2 only produces 2 ATP?

NADH molecules pump 3 protons into the intermembrane space as they pass through the Electron Transport Chain, resulting in the production of 3 ATP. FADH2, on the other hand, pumps only 2 protons, leading to the production of 2 ATP.

What is the total number of ATPs produced in the Electron Transport Chain?

The Electron Transport Chain produces a total of 34 ATPs. This is based on 10 NADH molecules producing 30 ATPs and 2 FADH2 molecules producing 4 ATPs.

How many ATPs are produced per molecule of glucose in cellular respiration?

A total of 38 ATPs are produced per molecule of glucose in cellular respiration, with 34 ATPs coming from the Electron Transport Chain, and 4 ATPs coming from glycolysis and the Krebs cycle.

Why do some cells only produce 36 ATPs instead of 38?

In some cells, such as muscle cells, 2 ATPs are consumed when NADH produced during glycolysis is transported into the mitochondria. This reduces the total ATP yield to 36 ATPs instead of 38.

What happens to the energy from glucose during cellular respiration?

The energy from glucose is primarily used to produce ATP, which serves as a source of energy for cellular functions. Some of the energy is also lost as heat, especially during physical activity.

Do prokaryotic cells perform cellular respiration, and if so, how?

Yes, prokaryotic cells also perform cellular respiration. Since they lack mitochondria, the process occurs across the inner part of their plasma membrane, where similar steps to the mitochondrial process take place.