Cellular Respiration

Cellular Respiration Overview

  • Cellular respiration is the sequence of metabolic reactions that converts food into energy in the form of adenosine triphosphate (ATP).

Respiration Stages

  • It is a three-stage process that includes glycolysis, the Krebs cycle, and the electron transport chain.

Glycolysis

  • Glycolysis happens in the cytoplasm, chopping glucose into two three-carbon molecules and generating a small amount of ATP.

Krebs Cycle

  • In the Krebs cycle, the three-carbon molecules are further broken down in the mitochondria, generating more ATP and liberating high-energy electrons.

Electron Transport Chain

  • The electron transport chain uses those high-energy electrons to pump protons out of the cellular matrix, forming a proton gradient that leads to ATP synthesis.

ATP: The Energy Currency

  • ATP—the cell’s energy currency—is used to power various cellular functions. Making and breaking of ATP offers an efficient way of storing and releasing energy.

Aerobic vs. Anaerobic Respiration

  • These processes are part of aerobic respiration, requiring oxygen to function. In conditions of low oxygen, an organism can switch to other methods like fermentation to generate ATP, collectively called anaerobic respiration.

Energy Production

  • While fermentation is overall less productive than aerobic respiration, it allows some organisms to live in low-oxygen environments.
  • However, efficient energy generation in most organisms, including humans, relies heavily on the oxygen-dependent stages of cellular respiration.

Interplay with Photosynthesis

  • In the larger context of life on Earth, the carbon dioxide and water produced during cellular respiration are used by plants during photosynthesis to generate glucose and oxygen.
  • This sets up a cycle where animals consume the oxygen and glucose produced by plants, and plants consume the carbon dioxide and water produced by animals.

Chemical Reactions

  • The overall chemical reaction for cellular respiration is: C6H12O6 + 6 O2 → 6 CO2 + 6 H2O + energy (ATP + heat).

Mitochondria: The Powerhouse

  • The mitochondria, where most of ATP synthesis occurs, are often called the “powerhouse of the cell”.
  • The efficiency and adaptability of cellular respiration pathways, together with the structure of the mitochondria, allow for cells to rapidly meet varying energy demands.