Amines and Nitriles
Introduction
Nitrogen atoms with a zero formal charge have three bonds on them. Amines are organic compounds that have a nitrogen atom with three single bonds on it. Amines have one or more alkyl or aryl groups attached to this nitrogen atom. If one carbon-based group is attached to the nitrogen atom, it is called a primary amine. If two carbon-based groups are attached to the nitrogen atom, it is called a secondary amine. If three carbon-based groups are attached to a nitrogen atom, it is called a tertiary amine.
Amines are found in many natural products and biologically important compounds.
Biologically important amines
Bases are one of the building blocks of RNA and DNA. Each is made up of four different types of bases. These bases are amine rings called purines and pyrimidines. Both RNA and DNA contain the purine bases guanine (G), adenine (A). Both RNA and DNA contain the pyrimidine base cytosine (C). The fourth base of RNA and DNA is ever so slightly different between the two. RNA contains the pyrimidine base uracil (U), while DNA contains the pyrimidine base thymine (T). Uracil and thymine only differ by one methyl group attached to the ring.
DNA/RNA Bases
Amino Acids, Peptides, Proteins
Polymers are biological compounds responsible for many different functions. Proteins like collagen and keratin are structural proteins needed for our skin, tendons, hair, and fingernails. Enzymes are proteins that catalyze biological reactions. Hemoglobin is a protein that transports oxygen throughout your body. Proteins like insulin are hormones. Proteins can even be toxic, like snake venom.
Amino acids are the building blocks proteins. There are twenty essential amino acids found in biochemistry. All amino acids have both an amine or amino end, a methane (CH) in the middle with some -R group attached to it, and a carboxylic acid end. That’s why they are named amino acids
Amino acid
Amino acids differ from each other by having different –R groups attached to them. Here are just a few of the twenty essential amino acids.
Several amino acids linked together are called peptides. A dipeptide is two amino acids linked together. Three linked together makes a tripeptide. An oligopeptide is a small chain of three to ten amino acids. A compound of many amino acids linked together into a polymer is called a polypeptide. Amino acids link together by amide bonds to form small chains called peptides.
Amino acids differ from each other by having different –R groups attached to them. Here are just a few of the twenty essential amino acids.
Several amino acids linked together are called peptides. A dipeptide is two amino acids linked together. Three linked together makes a tripeptide. An oligopeptide is a small chain of three to ten amino acids. A compound of many amino acids linked together into a polymer is called a polypeptide. Amino acids link together by amide bonds to form small chains called peptides.
When peptides are folded into molecules with a specific shape it can have a biological function. This folded molecule made of peptides is called a protein.
Porphyrin compounds
Four pyrroles linked together by one-carbon units forming a conjugated ring are called porphyrins. Porphyrins are interesting subunits in biological compounds. The four nitrogen atoms with their negative lone pairs of electrons are perfectly situated to hold large, positively charged metal ions. The high degree of conjugation makes them absorb visible light and makes these compounds colorful. A porphyrin ring that holds an iron atom is the main active unit of heme in hemoglobin. This gives our red blood cells their bright red color.
Porphyrin
Heme
Conjugated rings of four pyrroles with porphyrin-like structures are found in the biological compounds of vitamin B12 (cobalt metal and red color) and chlorophyll a (magnesium metal and green color).
Vitamin B12 is an essential water-soluble vitamin for our diets. Because it contains cobalt, the group of compounds that have vitamin B12 activity are collectively called the cobalamins. Vitamin B12 is commonly found in animal products like fish, meat, eggs, and milk. Notice the amines of the pyrroles in the central ring as well as the amide groups along the periphery.
Vitamin B12
Chlorophyll a is found in the chloroplasts of plant cells and is crucial for photosynthesis. Of course, chlorophyll allows the plant to absorb sunlight converting carbon dioxide to oxygen while synthesizing carbohydrates like glucose.
Chlorophyll
Sulfanilamides
Para amino benzoic acid (PABA) is a molecule used to synthesize vitamin B9 (folic acid). Humans can obtain vitamin B9 through our diets, but bacteria cannot. Bacteria have an enzyme called dihydropteroate synthase (DHPS) which is necessary to convert PABA to vitamin B9. Sulfanilamide is the simplest sulfa drug (an antibiotic). Notice how sulfanilamide has a very similar structure to PABA. It acts as a competitive inhibitor to the DHPS enzyme. Since it has a similar shape, it overwhelms the enzyme and the enzyme is unable to convert PABA to vitamin B9. The bacteria therefore have trouble growing. Sulfanilamide is therefore bacteriostatic. It doesn’t kill the bacteria. It only inhibits the bacteria’s ability to replicate and grow.
