Introduction - SS2 Biology Lesson Note

Respiration refers to the biological process by which organisms obtain energy from organic molecules and release waste products, particularly carbon dioxide and water. It is a vital process that occurs in all living cells and is essential for the production of ATP (adenosine triphosphate), the energy currency of cells. Respiration involves the oxidation of organic molecules to release energy for cellular activities.

There are two main types of respiration: aerobic respiration and anaerobic respiration.

1.       Aerobic Respiration:

·         Aerobic respiration occurs in the presence of oxygen and is the most efficient and common type of respiration.

·         It takes place in the mitochondria of eukaryotic cells and the cytoplasm of prokaryotic cells.

·         The process involves the complete breakdown of organic molecules (such as glucose) through a series of enzymatic reactions, resulting in the production of ATP, carbon dioxide, and water.

·         The overall chemical equation for aerobic respiration is:

·         Glucose + Oxygen → Carbon Dioxide + Water + ATP

 

2.       Anaerobic Respiration:

·         Anaerobic respiration occurs in the absence of oxygen or when oxygen supply is limited.

·         It takes place in the cytoplasm of cells and is less efficient compared to aerobic respiration.

·         Anaerobic respiration can occur through two different processes, depending on the organism:

a.       Fermentation: In organisms like yeast and certain bacteria, anaerobic respiration involves fermentation. Fermentation pathways include alcoholic fermentation, where pyruvate is converted into ethanol, and lactic acid fermentation, where pyruvate is converted into lactic acid. Fermentation generates a small amount of ATP.

b.       Anaerobic Respiration (Respiration without Oxygen): In some bacteria and archaea, anaerobic respiration involves the use of alternative electron acceptors, such as nitrate or sulfate, instead of oxygen. This process allows these organisms to produce energy in the absence of oxygen.