Aerobic Respiration

Aerobic Respiration

Aerobic Respiration Overview

  • Aerobic respiration is a set of metabolic reactions that convert biochemical energy from nutrients into adenosine triphosphate (ATP) and waste products.
  • This process involves the oxidation of glucose in the presence of oxygen.
  • The ATP produced provides energy for a variety of cellular processes.
  • Aerobic respiration is generally a more efficient process of energy production compared to anaerobic processes, such as fermentation and anaerobic respiration.

Stages of Aerobic Respiration

  • Glycolysis: This occurs in the cytoplasm and involves the breakdown of one molecule of glucose into two molecules of pyruvate. Provides a net gain of 2 ATP and also produces NADH. Does not require oxygen, hence can occur even under anaerobic conditions.
  • Link Reaction: This occurs in the mitochondrial matrix. Pyruvate is decarboxylated and combined with coenzyme A (CoA) to form Acetyl CoA. Carbon dioxide and NADH are also produced in this stage.
  • Krebs Cycle (or Citric Acid Cycle): Also occurs in the mitochondrial matrix. Here Acetyl CoA combines with oxaloacetate to form citrate. This leads to the production of ATP, NADH and FADH₂.
  • Oxidative Phosphorylation: It takes place in the mitochondrial inner membrane. NADH and FADH₂ are oxidised, releasing electrons which are transferred through the electron transport chain. This creates a proton (H⁺) gradient, which powers the synthesis of ATP by ATP synthase.

Key Points

  • In total, up to 38 ATP molecules can be produced from one glucose molecule during aerobic respiration.
  • Oxygen is the final electron acceptor in the electron transport chain, which allows aerobic respiration to continue. If oxygen is not present, the process must shift to an anaerobic pathway.
  • Some cells, such as skeletal muscle cells, can switch to anaerobic respiration (glycolysis and fermentation) when oxygen is scarce. This process yields less ATP but allows glucose breakdown to continue at a fast rate.
  • Hydrogen ions (protons) build up in the intermembrane space of mitochondria during the electron transport chain, leading to an electrochemical gradient which is essential for oxidative phosphorylation.
  • The energy for biological processes derived from aerobic respiration is indispensable for maintaining a variety of life’s functions, from muscle contractions to synthesis of biomolecules.