Internal Respiration vs. External Respiration
Main DifferenceThe main difference between internal respiration and external respiration is that internal respiration occurs within the cells of the body, whereas external respiration occurs between the external environment and cells of the body.
Difference Between Internal Respiration and External Respiration
Internal Respiration vs. External Respiration
Internal respiration occurs within the cells, whereas external respiration occurs between the external environment and body.
Internal Respiration vs. External Respiration
In internal respiration, oxygen diffuses out from the blood into the tissue; on the other side in external respiration, oxygen diffuses from alveolar air into the blood.
Internal Respiration vs. External Respiration
In internal respiration, the partial pressure of oxygen in the blood is reduced from the 100 mmHg to 40 mmHg whereas in external respiration, the partial pressure of the oxygen in the blood in increased from 40 mmHg to 100 mmHg.
Internal Respiration vs. External Respiration
In internal respiration, carbon dioxide diffuses into the blood from the tissues, whereas, in external respiration, carbon dioxide diffuses out from the blood into the alveolar air.
Internal Respiration vs. External Respiration
In internal respiration, correlation occurs only with the internal environment; on the other hand, in the external environment, correlation occurs with both internal and external environment.
Internal Respiration vs. External Respiration
In internal respiration, oxidation reaction takes place whereas, in external respiration, no oxidation takes place.
Comparison Chart
| Internal Respiration | External Respiration |
| Internal respiration is the exchange of gas across the respiratory membrane of the metabolizing tissues. | External respiration is the exchange of gases across the respiratory membrane of the lungs |
| Location | |
| In cells | Between the cells of the body and external environment |
| Breathing | |
| No breathing | Breathing occurs |
| Involvement of Hemoglobin | |
| The oxygen attaches with hemoglobin and offloading from heme of hemoglobin | No involvement |
| Oxidation | |
| Three oxidation processes: 1. Glycolysis 2. Krebs Cycle 3. Oxidative phosphorylation | No oxidation |
| Involvement of Oxygen | |
| Sometimes occur without the oxygen | Always oxygen involves |
| Gas Exchange | |
| No gas exchange | Gas exchange occurs |
| Chemical Reaction | |
| Photons combine with oxygen to form water | Oxygen combines with hemoglobin to form oxyhemoglobin |
| PO2 | |
| Reduced | Increased |
| PCO2 | |
| Increased | Reduced |
Internal Respiration vs. External Respiration
Internal respiration is the process in which oxygen diffuses from the blood into the intestinal fluid and the cells, on the other hand, external respiration is the process of exchanging oxygen and carbon dioxide in the lungs, gills, and other tissues exposed to the external environment. In internal respiration, the partial pressure of oxygen which is normally 100 mmHg in the blood reduced to 40 mmHg in tissues and creates a pressure gradient that causes oxygen to dissociate from hemoglobin, diffuses out of the blood, cross the interstitial space and enters the tissue. On the other hand, in external respiration, the partial pressure of oxygen increases from 40 mmHg to 100 mmHg and causes oxygen to rapidly cross the respiratory membrane from the alveoli into the blood. No breathing takes place in internal respiration, whereas respiration occurs in external respiration. Hemoglobin involves in the internal respiration whereas in external respiration no hemoglobin is involved. In internal respiration, PCO2 increases while in external respiration, PCO2 decreases. In internal respiration gas exchange does not take place on the other hand, in external respiration gas exchange takes place. Oxidation occurs in case of internal respiration while no oxidation occurs in external respiration.
What is Internal Respiration?
Internal respiration happens in the cells of the living body and involves all body cells. It consumes oxygen to break down molecules in order to release energy in the form of adenosine triphosphate (ATP). This type of respiration is also called cellular respiration as it occurs in the cells. Internal cellular respiration can occur in two forms; aerobic respiration, which needs oxygen and anaerobic respiration, which does not need oxygen, also known as fermentation. The cells of most living organisms cannot survive long periods of anaerobic respiration, and thus, oxygen is needed. Aerobic respiration generates a large number of ATP, whereas anaerobic respiration cannot produce very much energy (ATP). Most of the reactions of aerobic respiration occur inside the mitochondria of the cells. Aerobic respiration involves in three steps; glycolysis, Krebs cycle, and oxidative phosphorylation. Glycolysis is the splitting of sugar which happens in the cytoplasm. Krebs cycle occurs in the matrix of the mitochondria, whereas oxidative phosphorylation occurs across the membrane of the mitochondria. In the last step of anaerobic respiration (oxidative phosphorylation) electron transport chain is found which accepts the electron. Oxygen provides a force to drive the transport of electrons down the chain. As electrons move across the membrane, ADP is converted into ATP. IN internal cellular respiration, water and carbon dioxide are synthesized. Water is produced when protons combine with oxygen at the end of the electron transport chain.
What is External Respiration?
External respiration which is sometimes referred to as breathing that occurs between the external environment and the cells of the body. It consists of two steps; breathing and gas exchange. Breathing is also known as ventilation, which is the intake of oxygen into the body and expulsion of carbon dioxide out of the body. The gas exchange involves the exchange of gases between the blood capillaries and the alveoli of the lungs. The alveoli are thin-walled round shaped air sacs which occur in groups within the lungs. There are numerous air sacs which are packed together to enhance the surface area for gas exchange. Gases move in cells in external respiration. Oxygen which is inhaled diffuses from the alveoli into the blood of capillaries. Then oxygen attaches reversibly to the iron of the hemoglobin of the red blood cells. Carbon dioxide which combines to an amino acid in the blood offloads from the RBCs in order to be exhaled from the body. The blood cells transport the gases in the body. In this way, oxygenation of the body cells occurs and waste products removed. External respiration occurs in many animals, but some animals do not have lungs, for example, fish live in water have gills for respiration, and similarly, some animals use their skin for respiration. Oxygen is used in internal respiration, so external respiration is essential in keeping our cells alive. But a few animals can continue cellular respiration in the absence of oxygen.
ConclusionIt has concluded that both internal respiration and external respiration are types of gas exchange, but internal respiration occurs at the tissue level within the body, whereas external respiration occurs between the body and external environment.
