What are enzymes?
You may remember from a high school or college chemistry lab that when you performed an experiment using two or more chemicals, another chemical was often added to help the reaction to take place or to speed it up. That chemical was an enzyme. Enzymes are proteins and it is their job to regulate and accelerate most chemical reactions that occur in living things. Life itself would be impossible without enzymes.
Enzymes are called catalysts, meaning they speed up the rate of a reaction between two or more chemicals. A given chemical reaction between two chemicals may take place without an enzyme, but the rate of the reaction may be incredibly slow. It might take hours, days, weeks, or even years to happen. This would be simply unacceptable, as the proper functioning of our body may require that same chemical reaction to take place numerous times in a fraction of a second. Enzymes speed up the rate at which chemical reactions occur. Another important feature of enzymes is that they are extremely specific. Most enzymes will work on only one reaction, just as a key will fit into one lock.
Is it possible for chemical reactions to be linked together?
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In various situations in our body, many chemical reactions actually occur in series. Here, the product(s) of one chemical reaction become reactants in the next chemical reaction and so on. These reaction series are more commonly referred to as pathways, as depicted in Reaction Series Figure. Here A and B are the initial reactants and G and H are the end products of the pathway |
What is energy?
Energy may be best understood as a potential or presence that allows for some type of work to be performed. Some of energy’s more recognizable forms are heat, light, mechanical, chemical, and electrical energy. Without energy we simply would not exist. And, the universe if it existed would be a frigid, barren, motionless void.
Energy is neither created nor destroyed, however it can be converted from one form to another. This means that while the total amount of energy in the universe remains constant, the quantity of the different forms can change relative to one another. For instance, you are probably reading this book by the light of a nearby lamp. The light bulb has a thin filament inside which transforms the electrical energy running from the wall socket and through the cord to the filament in the bulb where it is converted into two other forms of energy—light and heat. As the filament illuminates, there is a reduction in electrical energy and an increase in light and heat energies. So energy is not lost but transformed to other forms.
A little bit closer to nutrition, food contains chemical energy in the form of carbohydrates, proteins, fats, and alcohol. Once inside our body the chemical energy of these substances can be transformed into mechanical energy to power muscular movement and other activities as well as heat to maintain our body temperature. Furthermore, we can store these energy molecules when we cannot immediately use them.
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