What is respiration? Define internal and external respiration

Respiration is a biochemical process in which the cells of living organisms use oxygen and glucose to produce ATP (energy), releasing carbon dioxide and water as byproducts. The energy generated powers essential body activities such as walking, running, sitting, digestion, and other organ functions, making respiration vital for survival.

Respiration in Humans

In humans, respiration begins with the inhalation of air through the nostrils, which passes into the nasal cavities, down the windpipe (trachea), and into the lungs.

• Breathing is a mechanical part of respiration and refers to the inhalation and exhalation of air.
• During inhalation, the lungs expand as air enters, and during exhalation, they return to their original size as air exits.
• The respiratory organs enable the exchange of gases (oxygen and carbon dioxide), though this process differs among organisms.

Types of Respiration

1. External Respiration
   • Occurs between the cells of the body and the external environment.
   • Involves breathing and gas exchange.
   • Cannot occur without oxygen.
2. Internal Respiration
   • Takes place inside body cells.
   • Involves the utilization of oxygen to release energy from glucose.
   • Does not involve the physical act of breathing, and in some cases, may occur in low-oxygen conditions.