Respiration

Respiration

Respiration is a vital cellular process where energy stored in organic substances is made available for biological processes. It is the main way that energy is released from glucose so that all the other chemical processes needed for life can happen.

Glycolysis

  • Glycolysis is the first stage of respiration and happens in the cytoplasm of cells.
  • It is the process of breaking down one glucose molecule into two molecules of pyruvic acid.
  • Four molecules of adenosine triphosphate (ATP) are produced, but the net production is two ATPs since two are required to start the process.
  • It also results in the production of two NADH molecules.
  • The link reaction is the bridge between glycolysis and the Krebs cycle.
  • It occurs in the mitochondria and involves decarboxylation and dehydrogenation of pyruvate to produce acetyl CoA.
  • One molecule of carbon dioxide is released and one NADH is produced per pyruvate molecule.

Krebs Cycle

  • The Krebs Cycle is the second major stage of respiration, occurring in the mitochondria.
  • Each turn of the cycle produces one ATP, three NADH, and one FADH₂.
  • Two molecules of carbon dioxide are also released in the process.
  • The cycle turns twice for each glucose molecule, as there are two pyruvate molecules produced in glycolysis.

Electron Transport Chain

  • The Electron Transport Chain (ETC) takes place along the inner mitochondrial membrane where NADH and FADH₂ are oxidised.
  • Electrons flowing through the chain power the pumping of hydrogen ions from the matrix into the intermembrane space, creating a concentration gradient.
  • The hydrogen ions flow back into the matrix through ATP synthase, powering ATP production.
  • Oxygen serves as the final electron acceptor at the end of the chain, producing water when it combines with the hydrogen ions and electrons.

Anaerobic Respiration

  • Anaerobic respiration occurs in the absence of oxygen, and while less efficient, can provide a rapid burst of ATP energy.
  • In muscle cells, pyruvate is reduced to lactic acid. This process allows the continued production of ATP by glycolysis in the short term.
  • In yeast cells, pyruvate is converted to ethanol and carbon dioxide in a process called alcoholic fermentation.

Importance of Respiration

  • Respiration provides the energy necessary for all biological processes, including active transport, protein synthesis, DNA replication, muscle contraction, and thermoregulation.
  • The carbon dioxide produced is used by plants in photosynthesis, and the water produced helps to maintain homeostasis.
  • Inefficient or interrupted respiration can lead to energy deficits, cell damage, and lead to various diseases.

Remember, understanding the transformations and transfer of energy in respiration can provide insights into both the functions and dysfunctions of biological systems.