Action and function of enzymes
At low temperatures, such as body temperature, chemical reactions are (too) slow. In your body, enzymes (biocatalysts) ensure that these reactions take place quickly enough. They do this by lowering the activation energy, which is the minimum amount of energy required for a reaction to proceed.
Enzymes bind to the substrate (this is how the substance or substances to be converted are called). This binding causes small changes in the substrate molecules, making them react (split or divide) more easily. The enzyme is then usable again. That is why it is also important not to change the protein form. When the spatial shape of the enzyme changes, the substrate no longer fits and the enzyme activity is lost. Because of the tertiary structure, they have a specific shape and therefore only fit on one substrate (substrate-specific).
In addition, enzymes reaction specific. This means that they only accelerate one particular reaction. When enzyme X catalyzes (accelerates) the binding of substances A and B, it cannot bind substance A with substance C (there are exceptions to this rule, but that’s a little too deep for this article). This is because it cannot fit well into the structure of the enzyme, so that no binding takes place with the enzyme and then with another substance. It is also possible that only one substance, set substance D, fits in the enzyme and this is split into substances K and M by the enzyme.
Acidity (pH) and temperature: effect enzymes
The pH and the temperature also have a great influence on the functioning of enzymes, because in enzymes there are numerous weak bonds. Think of hydrogen bonds, ionic bonds (break at a high pH, more on that later) and sulfide bonds (break at high temperature). The proteins denature (become damaged) when the bonds can no longer be maintained. As a result, they lose their structure and can no longer fulfill their original task. This mainly relates to the aforementioned tertiary structure (see also the previous learning objective).
Proteins (including enzymes) react as a buffer: at a low pH they absorb H + ions, at a high pH they release H + ions. In this way their charge changes and therefore the spatial structure of the protein chain. The has direct consequences, as stated earlier, for the shape and functioning of enzymes. For each enzyme there is one pH at which that enzyme works best, that is called the optimum pH mentioned. This can be plotted on a graph, the optimum curve (it resembles the clock of the normal distribution in probability theory). In front of nucleic acids (RNA, DNA) is the same as the proteins, because they also have a certain shape that is sensitive to temperature and acidity.