Summary
Highlights
The body is composed of large biomolecules like proteins, carbohydrates, lipids, and nucleic acids. Most are polymers, which are long chains made of repeating units called monomers. Understanding these monomeric units is crucial for comprehending biochemistry. Amino acids are the first type of monomer discussed.
Amino acids have a characteristic structure: an amino group on one end, a carboxyl group on the other, and a central alpha carbon. This alpha carbon is attached to an 'R-group' or side chain which varies for each amino acid. Examples include glycine (R-group is hydrogen) and alanine (R-group is a methyl group).
There are approximately 20 common amino acids, each with a unique R-group. These R-groups determine the amino acid's properties, categorizing them as hydrophobic (e.g., leucine), aromatic (e.g., phenylalanine), basic (e.g., lysine), acidic (e.g., aspartic acid), or nucleophilic (e.g., serine). The R-group variation dictates the characteristics of the proteins they form.
Some amino acids cannot be synthesized by the human body and must be obtained through diet; these are called essential amino acids. Others can be produced internally and are thus non-essential.
In biological environments, amino acids exist in different ionic forms due to the protonation and deprotonation of their amino and carboxyl groups. The amino group is basic and can be protonated (NH3+), while the carboxyl group is acidic and can be deprotonated (COO-). This leads to cationic, anionic, and zwitterionic forms.
The specific form an amino acid takes depends on the pH of its environment. Acidic conditions favor the cationic form, while basic conditions favor the anionic form. At physiological pH, which is close to neutral in the body, the zwitterionic form (possessing both a positive and negative charge) is dominant. Side chains can also have varying protonation states depending on pH.
Amino acids, with the help of other molecules in the body, polymerize to form proteins. The video concludes by stating that the next step is to learn about proteins.