When you add up all the energy flows in living organisms and make a worksheet that breaks them down by scale, it becomes clear that you can predict a lot about the future. If we take living cells as an example, the cells become damaged by constant change and turnover. The amount of damage caused by cell-to-cell variation is known as the Replication Constant.
If you add up the total Replication Constant of all living cells (the sum of all replication ratios) then you get the total energy transfer in living organisms. This is an indicator of the number of ATP molecules generated each second. You should not be too surprised if you have heard of the cell’s energy capacity. This is the basis for our everyday activities.
All systems in life-cycle work on this principle of energy transfer. Every living system needs energy and converts it into something useful, in order to make an organism function.
The two most important forms of energy transfer are the chemical and the mechanical. There are many other smaller forms, like infrared radiation, etc. But in general we will use the term ‘energy’ to refer to either one or the other.
The process of energy transfer in living organisms is nothing new; there has been an energy transfer ever since matter and energy came together. We need to understand this basic concept before we can start to look at the big picture and consider the transition from living organisms to our everyday world.
Chemical energy is basically a way of transferring one form of energy to another. Chemical energy is used to create heat, to create motion, to produce electricity, to produce sound, to form chemical bonds, etc.
Mechanical energy is just one type of energy that can be transferred. It comes from mechanical energy and chemical energy, which come from some other source. But even with mechanical energy, the transfer of energy from one form to another is a major part of the process.
The major source of energy is energy from sunlight, water, nuclear energy, wind, etc. And the major source of mechanical energy is energy from friction. All these sources of energy are used in living organisms in order to do work.