Biology SS 2Week 1
Topic: Respiratory System
Introduction
Respiration is defined as a biochemical activity of the cell in which glucose is broken down by a series of reactions controlled by enzymes to release energy.
Your respiratory system is made up of the organs in your body that help you to breathe. Respiration means Breathing. The goal of breathing is to deliver oxygen to the body and to take away carbon dioxide. The lungs are the main organs of the respiratory system.
Oxygen is breathed in and it breaks down the food substances (glucose) to release energy, carbon dioxide and water. Carbon dioxide and water are regarded as waste products of respiration. The energy so released is used by living organisms for various life processes. This occur inside a tiny organelle called the mitochondrion.
Phases or Stages of Respiration
Respiration takes place in two phases or stages. These are external and internal (tissue) respiration
External respiration (Breathing): Is defined as the exchange of gases between the environment and the respiratory organs of living organisms. It simply involves the breathing in of air or oxygen into the respiratory organs such as lungs or gills otherwise called inspiration or inhalation and the breathing out of carbon dioxide and water vapour into the atmosphere otherwise called expiration or exhalation.
Internal (Tissue) respiration: Is defined as the oxidation of organic food substances within the cells leading to the release of energy, carbon dioxide and water. It takes place when the oxygen taken in is used up by the individual cells in the body for the oxidation of food substances. Carbon dioxide, water and energy are given out by these cells in return.
Internal, tissue or cellular respiration can be represented by the equation:
C6H12O6 + 6O2 ——> 6H2O + 6CO2 + Energy
(Glucose) (Oxygen) (Water) (Carbon dioxide) ATP
In summary, the main purpose of respiration is to generate energy required by the body for various life processes.
Types of Respiratory System
The structures used by different organisms depend on their position in the evolutionary set up. The unicellular organisms tend to have simpler mode of respiration than the multicellular due to their increased surface area relative to volume. Organisms adopt different types of respiratory systems depending on their types, complexity, size and the habitat in which they are found.
Different Organisms and their Respiratory Structures
| Organisms | Respiratory system/organ |
| Unicellular organisms, e.g. Amoeba and Paramecium | Body surface |
| Hydra and tapeworm | Cell membrane |
| Earthworm | Wet skin or body surface |
| Fishes, e.g. Tilapia | Gills |
| Arthropod, e.g. Insects | Tracheal system |
| Arachnids, e.g. Spiders | Lung books |
| Tadpoles | Gills |
| Reptiles, e.g. Lizard | Lungs |
| Amphibians, e.g. Toads and frogs | Mouth, skin and lungs |
| Aves, e.g. Birds | Lungs |
| Mammals | Lungs |
| Flowering plants | Stomata and lenticels |
Respiratory Surface
The respiratory surface refers to the definite surface of the body such as the surface of the lungs or a gill where gaseous exchange takes place.
Characteristics of Respiratory Surfaces
- Respiratory surfaces, be it in plants or animals must have the following characteristics:
- Respiratory surfaces must be moist because gases diffuse in solution through them
- It must be permeable to allow gases to pass in and out of them
- It must be thin-walled to shorten diffusion distance and make diffusion easier and faster
- It must have adequate supply of transport medium, e.g. blood
- It must have a large surface area to aid easy diffusion of gases
- Respiratory areas must be highly vascularised, i.e., equipped with capillaries or similar network to bring in or take away diffused gases.
