Difference Between Internal and External Respiration

The key difference between internal and external respiration is that the internal respiration refers to the set of metabolic reactions that occur within the cells to produce energy via the oxidation of glucose and other organic molecules while external respiration refers to the process of moving oxygen from external environment to the cells and moving carbon dioxide from the body to the external environment.

When you hear the term respiration, it may remind you the process called breathing. That is the process of inhaling and exhaling air. However, other than this process, there is another respiration process that occur inside the cells of the organisms. It is the process called cellular respiration. Hence, these two processes, breathing and cellular respiration, are termed as external respiration and internal respiration respectively. There are differences between internal and external respiration in many aspects. Nevertheless, internal and external respiration relate with each other since the internal respiration uses the oxygen that comes through external respiration, and external respiration removes carbon dioxide; a byproduct of the internal respiration.

CONTENTS

1. Overview and Key Difference
2. What is Internal Respiration
3. What is External Respiration
4. Similarities Between Internal and External Respiration
5. Side by Side Comparison – Internal vs External Respiration in Tabular Form
6. Summary

What is Internal Respiration?

Internal respiration, also known as cellular respiration, is the process of energy production via the breakdown of glucose. Therefore, it occurs within the cells. Internal respiration can be aerobic respiration or anaerobic respiration. Aerobic respiration needs oxygen since it is the final electron acceptor of the final stage of the aerobic respiration. Anaerobic respiration occurs when the oxygen is absent. Aerobic respiration produces more ATP molecules while anaerobic respiration produces very less amount of ATP.

Aerobic respiration has three major stages, which occur one after the other using the products of the previous stage. They are glycolysis, Krebs cycle and electron transport chain. Glycolysis occurs in the cytoplasm of the cells while Krebs cycle and electron transport chain take place inside the mitochondria.

At the end of the aerobic process, it produces a total of 38 ATP molecules, which can be used by the body for all the activities which require energy. Furthermore, it produces carbon dioxide and water as byproducts.

What is External Respiration?

External respiration is a physical process of taking oxygen from the external environment into the body and expelling carbon dioxide from the body to the external environment. It is a vital process for life as it supplies oxygen to extract energy from food via internal or cellular respiration. Additionally, it removes carbon dioxide, which is a waste product of internal respiration. In addition, external respiration removes excess water from the body through exhalation.

Thus, external respiration has three steps namely inhalation, exhalation, and relaxation. Inhalation is an active process while exhalation is passive. Furthermore, it involves two stages known as ventilation and gas exchange. Ventilation is the movement of the air in and out of the lungs. Gas exchange takes place in the alveoli of the lungs. Two things happen during the gas exchange; oxygen goes into blood and carbon dioxide diffuses out into lungs.

External respiration is a voluntary action, which the animal can control. However, animals do not always voluntarily breathe, but it is an ever happening involuntary process as the centres of the brainstem automatically regulate the external respiration.

What are the Similarities Between Internal and External Respiration?

• Internal and External Respiration involve oxygen and carbon dioxide.
• These processes occur in living organisms.

What is the Difference Between Internal and External Respiration?

The fundamental difference between internal and external respiration is in the process and the product. Internal respiration is a set of metabolic processes that occur within the cells while external respiration is the physical process of inhalation, gas exchange and exhalation. This is the key difference between internal and external respiration. Another difference between internal and external respiration is that the internal respiration produces energy molecule ATP while the external respiration does not produce or use energy.

Summary – Internal vs External Respiration

Internal and external respiration are two types of respiration processes in which internal respiration occurs inside the cells while external respiration occurs between the body and the external environment. Internal respiration is the process of breaking down of glucose at the cellular level to produce energy. Thus, it can be aerobic or anaerobic based on the presence and absence of oxygen. On the other hand, external respiration is a mechanical process that includes inhalation, gas exchange and exhalation. Both processes relate to each other. External respiration provides oxygen to internal respiration as well as it removes carbon dioxide that produced by the internal respiration. This is the difference between internal and external respiration.

Reference:

1.“Cellular Respiration:” Chapter 3 – Proteins. Available here  
2.Stöppler, Melissa Conrad. “Human Lung Anatomy: Lung Structure, Lobes & Function.”MedicineNet. Available here  

Image Courtesy:

1.”Cellular respiration”By Darekk2 – Own work, (CC BY-SA 3.0) via Commons Wikimedia  
2.”2316 Inspiration and Expiration”By OpenStax College – Anatomy & Physiology, Connexions Web site. Jun 19, 2013. (CC BY 3.0) via Commons Wikimedia