Chemical reactions occur not only in nature but also inside human bodies. Biochemical reactions power the living creatures and drive our bodies to carry out day to day tasks. Here are 10 important chemical reactions without which humans can’t survive:

1. Respiration:

The lungs and respiratory system allow us to breathe. They bring oxygen into our bodies (called inspiration, or inhalation) and send carbon dioxide out (expiration, or exhalation). This exchange of oxygen and carbon dioxide is called respiration. With the help of respiration, an organism obtains energy (in the form of ATP and NADPH) in which oxidation of nutrients happens and then releases waste products. And thus it makes it one of the ten important chemical reactions in the human body.

2. Digestion: One of the ten important chemical reactions

Digestion refers to the breakdown of food into smaller components that are absorbed into the bloodstream. This digestion or catabolism is of two types: the mechanical digestion of food that occurs in the mouth where it is physically broken up into smaller pieces. And chemical digestion occurs in the gastrointestinal tract when the digestive enzymes break down the food into smaller molecules.

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3. Ligation Reactions:

Ligation reactions use the energy of ATP to join two molecules together. An example of this kind of reaction is the joining of the amino acid with the transfer RNA (tRNA) molecule during protein synthesis.  During protein synthesis, the tRNA molecules bring each of the amino acids to the ribosome where they can be incorporated into the newly growing protein sequence. To do this, the tRNA molecules must first be attached to the appropriate amino acid.

4. Hydrolysis Reactions:

The term hydrolysis means to break apart with water. Since water is also a resulting product of these reactions, we also call condensation reactions. The formations of the major classes of macromolecules in the body (proteins, carbohydrates, lipids, and nucleic acids) are formed through dehydration synthesis where water is removed from the molecules. During normal digestion of food molecules, the major macromolecules break into their building blocks through hydrolysis.

5. Enzyme-Mediated Reactions:

The most important property of enzymes is to increase the rate of chemical reactions occurring in living organisms. Scientists call it catalytic activity. Enzymes speed up the rate of reactions because they lower the energy required to get to the transition state of the reaction.  The transition state of the reaction is an unstable intermediate structure formed during the reaction process. When enzymes or catalysts are present, the transition state energy is lowered which in turn has an exponential effect on the reaction rate. Thus, enzymes can increase the reaction rate by many orders of magnitude.

6. Production of ATP:

Organic molecules that contain a lot of carbon and hydrogen bonds have high energy potential and the ability to be oxidized to CO2 and water. Of all the major macromolecules, fats have the highest hydrocarbon content and thus, contain the largest energy potential (9 Cal/g). Proteins and carbohydrates have many more heteroatoms, such as oxygen and nitrogen incorporated into their structures, and have less energy potential (4 Cal/g for both proteins and carbohydrates). The processes of oxidation and reduction are critical for life.

7. RNA biosynthesis:

RNA synthesis, or transcription, is the process of transcribing DNA nucleotide sequence information into RNA sequence information. RNA synthesis is catalyzed by a large enzyme called RNA polymerase. The basic biochemistry of RNA synthesis is common to prokaryotes and eukaryotes, although its regulation is more complex in eukaryotes. And there is a close connection between prokaryotic and eukaryotic transcription. This is illustrated in a recently determined three-dimensional structures of representative RNA polymerases.

8. Oxidative phosphorylation:

As food is ingested, the large macromolecules (proteins, carbohydrates, and lipids) get digested into their monomer units. The monomer units, such as glucose from starch or fatty acids from TAGs, are delivered to cells. And are used as energy sources to regenerate ATP from ADP. This regeneration process is called oxidative phosphorylation. The term oxidative is used because the food molecules fully oxidize into carbon dioxide (CO2) during the process to release energy. Phosphorylation is the process of adding a phosphate group to a molecule. In this case, the energy that is harvested from the oxidation of the food molecules, specifically the electrons and protons, is used to phosphorylate ADP back into an ATP.

9. Allosteric regulation:

Allosteric regulation of enzymes occurs when the binding of a molecule to a different location from the active site causes a change in enzymatic activity. This type of regulation is either positive or negative and increases or decreases the activity of the enzyme. So, most enzymes that display allosteric are metabolic enzymes involved in the degradation or synthesis of specific cellular molecules. In allosteric inhibition, the binding of a molecule to the allosteric site causes a shape change. It reduces the affinity of the enzyme for the substrate and in contrast, an allosteric activator causes a conformational change.

10. Group Transfer Reactions:

In group transfer reactions, a functional group is transferred from one molecule and serves as the donor molecule for the acceptor molecule. The transfer of an amine functional group from one molecule to another is a common example of this type of reaction. And a common group transfer reaction in biological systems is used to produce α-amino acids and is used for protein synthesis. In this reaction, one α-amino acid serves as the donor molecule and a α-keto acid (these molecules contain a carboxylic acid functional group and a ketone functional group separated by one α-carbon) serves as the acceptor. In the acceptor molecule, the carbonyl oxygen is replaced with the amine functional group, whereas in the donor molecule, the amine functional group is replaced by oxygen forming a new ketone functional group.