One of the most important characteristic of life is respiration. All living organism requires respiring till death. A continuous supply of energy is essential for various activities of the living organisms. The process of respiration in which the potential energy stored in food materials is converted to kinetic energy by their oxidation.
So, respiration is a process by which energy is released as a result of oxidation of food within a leaping organism.
What is energy currency?
The source of energy in a cell is the food materials i.e. Carbohydrate, fat and protein. The energy remains stored in the covalent chemical bonds of these compounds. These compounds are oxidised during respiration and their covalent bonds are broken to release the energy store in them. A part of the released energy is trapped in high energy phosphate bonds (--P) of adenosine tri-phosphate (ATP) which is formed by joining adenosine di-phosphate (ADP) and inorganic phosphate (Pi). The energy stored in ATP is used for various activities of the cell. When energy is required ATP is hydrolysed into ADP + Pi. As ATP is available at ready form of chemical energy, it is called energy currency of a cell.
ATP contains two high energy prospect bonds (--P) that are placed terminally. The published values or energy content in each --P or ATP vary between 7 to 8 kcal. During the formation of each ATP from ADP + Pi, 7.6 kcal is captured and this amount of energy is released when ATP is hydrolysed to ADP + Pi.
What is the relation between Photosynthesis and Respiration?
Respiration is a catabolic process and is basically reverse of photosynthesis and the photosynthesis is an anabolic process. During photosynthesis, carbon dioxide and water are combine with the help of solar energy to form sugar and oxygen is evolved. On the contrary, respiration is is a continuous process in which sugar is usually oxidised by oxygen and broken down into Carbone dioxide and water along with liberation of energy. Photosynthesis occurs only in chlorophyll containing cells during daytime that is, in presence of sunlight. Generally the plant cells contain the chlorophyll. Respiration occurs in all living cells throughout day and night.
In green plants during daytime the carbon dioxide (CO2) produced by respiration is used up in photosynthesis and carbon dioxide is not evolved at that time. Moreover, in the daytime, the rate of photosynthesis becomes much higher than the rate of respiration. As a result the carbon dioxide released in respiration is not adequate to meet the photosynthetic requirement of CO2. To meet up is requirement green plants absorb carbon dioxide from atmosphere during the daytime and at the same time add oxygen (O2) to the atmosphere as the oxygen released in photosynthesis exceeds the respiratory requirement. In this process the green plants purifies the atmosphere by removing the carbon dioxide and adding oxygen. But, this does not happen at night as there is no photosynthesis in absence of sunlight but secretion continues so that green plants take up oxygen from the atmosphere and release carbon dioxide into it. The carbon dioxide produced by respiration of trees at night trends to settle down as carbon dioxide gas is heavier than air.
So, it is easy to say that sunlight is the ultimate source of energy for all biological systems. Solar energy is stored as potential energy within the food materials manufactured during photosynthesis. Respiration is the process responsible for release of this energy for biological systems.
What is compensation point?
The term compensation point refers to that point of light intensity at which the rates of respiration and photosynthesis in green plants become equal so that there is no exchange of gases between the plant and the atmosphere. So, at this point of light intensity, there is no exchange of carbon dioxide and oxygen between the plants and the environment.