7.1 - Energy Production through Cellular Respiration

Respiration is a vital process in all living organisms. Energy is required by all living organisms to carry everyday activities and living processes such as

• Waste products excretion
• Cell division
• Active transport of substances
• Muscle contraction
• Transmission of nerve impulses
• Synthesis of biomolecules in the body
• Absorption of digested food
• Maintenance of normal body temperature.

The Main Substrate in Energy Production

Cellular respiration , also known as internal respiration is a process in which energy needed is made available to all living cells. It involves the process of oxidation of organic molecules which releases the chemical energy stored within them. Note that the energy produced is not used directly. It has to be integrated into energy-carrying molecules called adenosine triphosphates (ATP). ATP can then be used by cells to carry out living processes. Glucose is the main substrate used in cellular respiration in both animals and plants.

• In humans and animals, the source of glucose comes from the carbohydrates consumed.
• In plants, glucose comes from the process of photosynthesis.

Figure 1 - Digestion of carbohydrates (left) produces glucose (energy source) for all body cells. Green plants carry out photosynthesis (right) to produce glucose (energy source) for other living processes.

Types of Cellular Respiration

There are two types of cellular respiration:

Fermentation is another process carried out by microorganisms such as yeast. We will further discuss the process of fermentation later.