Evolution of Enzymes
Image credits belong to: aitoff | Pixabay
Important terms to learn:
Reactant- is a substance that exists at the beginning of a chemical reaction. Reactants sit on the left side of the arrow in the equation, whereas products sit on the right side of the arrow in an equation. For instance: zinc and sulfur will react in combination to make zinc sulfide. Zinc + sulfur → zinc sulfide (Zn + S → ZnS)
Enzymes- are proteins naturally produced in the body that expedite the chemical reactions that underpin life. Enzymes are also catalysts. They are responsible for muscle-building, toxin destruction, and the physical decomposition of food particles during digestion. Enzymes and their ability to speed up chemical reactions were essential to the evolution of life billions of years ago. See more below.
Catalysts- are the agents that diminish the barrier that stops the chemical reaction event.
Substrates- are like a basis situated underneath the acting enzyme. It is installed in the binding region of the enzyme and allows for bonds that are easily and quickly producible and breakable. Nearly every molecule is a substrate at some point in our bodies. Every reaction requires a particular enzyme to aid its process; otherwise, the reactions would be too slow.
Metabolites- are the in-between or end result of metabolism and are involved in fueling, structuring, signaling, stimulating, and inhibiting enzymes.
Chemical reactions- are processes that take in and liberate energy. Energy is added to start chemical reactions. Energy is liberated in the form of heat or light to break chemical bonds.
Allosteric regulation- regulates an enzyme by attaching a small molecule at a site different from its active site, allowing cells to govern their biochemical direction and rates.
Activation energy- is the lowest amount of energy necessary for causing a reaction in atoms and molecules.
Law of Mass Action- expresses that the reaction rate is equivalent to the end result of the concentrations of the substances at the beginning of the chemical reaction. Lab-based chemical reactions will eventually achieve equilibrium or when the rates are the same between forward and backward reactions.
Affinity- is colloquially and intuitively understood as a natural liking, attraction, or relationship between two things or people. In a biological context, this is the strength by which any number of molecules come together. Catalysts have an affinity for their substrates. The affinity brings the reactants together expeditiously, which increases chemical reaction rates, all of which could not otherwise occur in just random molecular motion. The lock-and-key analogy for enzyme-substrate binding demonstrates a great affinity. The precisely evolved shapes of enzymes make them more efficient than the inorganic catalysts with weak, generic attractions. Silver and platinum, for instance, would include metallic, inorganic catalysts.
The absorption and liberation of heat, light, and energy occur either exothermically or endothermically. Exothermic reactions liberate more energy than they absorb. An example would be cellular respiration that involves glucose sugar combined with oxygen preceding energy liberation that leads to carbon dioxide and water.
C6H12O6 (glucose sugar) + 6O2 (oxygen) → 6CO2 (carbon dioxide) + 6H2O (water)
Water that is added to adenosine triphosphate (ATP) will break it down into adenosine diphosphate (ADP) which subsequently liberates energy (heat) to warm up the body.
Endothermic reactions absorb more energy than they liberate. Photosynthesis would be an example, which we see in plants that take in sunlight to make glucose sugar.
6CO2 (carbon dioxide) + 6H2O (water) → C6H12O6 (glucose sugar) + 6O2 (oxygen)
Although the body needs to be warmed up to avoid becoming too cold, it cannot use heat as a catalyst. Too much heat can denature or unravel the structure of proteins. As the structure or shape is highly crucial to protein function, it cannot be refashioned into the original shape. Our proteins' denaturation as caused by heat would lead to the cessation of our chemical reactions and eventually our death.
The enzymatically induced speed of chemical reactions is momentous to the evolution of life. In 2008, Richard Wolfenden, a North Carolina University professor of biochemistry and biophysics, reportedly believed that DNA and RNA based biology would require 78 million years to develop in the absence of enzymes.
I quote him as saying:
"Now we've found a reaction that – again, in the absence of an enzyme – is almost 30 times slower than that," Wolfenden said. "Its half-life – the time it takes for half the substance to be consumed – is 2.3 billion years, about half the age of the Earth. Enzymes can make that reaction happen in milliseconds."
Hemoglobin and chlorophyll could not be biologically synthesized or made without this reaction. Uroporphyrinogen decarboxylase was the enzyme used to speed up the making of chlorophyll and hemoglobin in cells.
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