 enzymes, the biological catalysts, first the contents, definition of enzymes, chemical nature of enzymes, enzymes as biological catalysts and the specificity of enzymes. So first the definition of enzymes. So enzymes are the biomolecules which increase the reaction rate or they increase the reaction of biochemical reaction within the living organisms. So students if we talk about simple words, then enzymes they are present in living organisms, they are biomolecules and their job is to increase the speed or rate of biochemical reactions. So without enzymes, if we talk about enzymes without enzymes the reaction rate will be too slow, biochemical reactions will be very slowly proceeded and life will be too long to sustain or continue. So catalytic power of enzymes is much more than the chemical catalysis. The chemical catalysis that we use in chemical reactions, in physics or in chemistry, the reaction rate or speed of reaction of the biochemical catalysts are very high. They may be in thousands, they may be in millions. So what is the nature of chemical nature of enzymes? So all the enzymes, they are biological molecules, two types of most of the enzymes, they are protein in nature, while a few enzymes they are also made up of the nucleic acid, that is the RNA molecules. So we can simply say that most of the enzymes, they are protein in nature. Protein in nature, the structure of protein, the same structure of enzymes, that is the primary structure of protein, the structure of enzymes because they are also made up of proteins. The secondary and tertiary structure of protein is similar to the secondary and tertiary structure of enzymes. And the most tertiary structure of enzymes is in the global form, the global proteins. If we look at the location of enzymes within the cell, the most of the enzymes, they are present in the soluble form. If there is an enzyme in cytoplasm, then there is a soluble form in cytoplasm, in this way, if there is an enzyme in mitochondria, then there is a soluble form in the matrix of mitochondria. The enzyme that is found in the nucleus, in the nucleus, in the aqueous environment, then most of the enzymes are water soluble, that is why they are found in the aqueous form. Few of the enzymes, Chandik enzymes are also membrane-bounded, they are not freely present in the cell, but they are attached with some membranes. Some of the enzymes, they are not protein in nature, they are actually RNA in nature. The enzymes that are made up of RNA are called ribozymes. Ribozymes are probably the most simplest enzymes or when we talk about the origin of life, the first enzymes that are thought to be working in the cells, they are actually the ribozymes. Enzymes are biological catalysts. If we define life as a biochemistry, a biological definition is that life is the name of continuous series of chemical reactions. That is, life sustains until biochemical reactions in our body continue. None of the biochemical reactions are in the living organisms that are without the involvement of enzymes, because if the enzymes are not catalyzed by reaction, then the reaction will be too slow. It will be so slow that as you speak, the food that we take is digested. Our digestive system has enzymes for food digestion. If the enzymes are not digested, then this food will be digested for many days and our body will not be able to take the nutrients that are needed in the food. The simple meaning of this is that in the absence of enzymes, when any process does not continue at such a high speed, it does not work at such a high speed as its requirement is, there is energy production. If the enzymes are not there, then the amount of energy produced in the body will be very less, which will not be able to proceed with our biochemical reactions or overall body activities. The catalytic power of enzymes is basically because they lower the activation energy. When we say that the enzymes speed up the reaction rate, then the simple rule of speed up is that they decrease the or they lower the activation energy. If the activation energy is less, then the reaction rate will automatically increase and the reaction speed will increase. Here we have the diagram. You can see the diagram of how the enzymes perform their activity. The red line is indicating the reaction without the enzyme. Without the enzyme reaction, you can see that the transition state is at a high level of the energy. That is, the activation energy is more. When the state of the enzyme is present, we call it the ground level. From the ground level to the transition level, this is the amount of activation energy. Now in this diagram, when there is enzyme, when the enzyme is present, it will lower the activation energy. This transition state will come down, which will ultimately lower the activation energy. In the presence of the enzyme, you can see that less than half of the activation energy required in both the common amounts is to proceed with the reaction. This is a simple way. The role of enzymes as catalysts is basically that the enzymes decrease the activation energy. They lower the activation energy because of which the enzyme speeds up. Specificity is the enzyme. If we talk about the specificity of the enzyme, then the enzymes are very specific. Specific means that every enzyme reacts with a specific substrate. There is a specific enzyme for every substrate. So, except for one substrate, the other doesn't react with another substrate. It doesn't convert it into a product. Because every enzyme, it has its very specific substrate, which will be converted into product. So, on this basis, we say that the enzymes are very specific. For example, if we talk about that enzyme, which is a break down enzyme of glucose, a phosphorylation of glucose. If we take the example of glycolysis, the glucose becomes 6-phosphate. So, the enzyme there is hexokinase. Now, from the glucose 6-phosphate to the fructose 6-phosphate, there will be a different enzyme there. So, for every reaction, for every substrate, there is a specific enzyme. Mostly, enzymes react with their own specific substrate. There are a few enzymes that can react with more than one substrate. Usually, we call them broad range enzymes. They are broad range, whereas they are less specific. So, they are less specific. Their number is very low, whereas most enzymes are very specific.