A Complete Guide to Amino Acids for the MCAT
Amino acids are organic molecules that form the building blocks of proteins. There are 20 essential amino acids that are commonly found in living organisms, and they can be categorized based on their chemical properties. These amino acids play an important role in biology, and understanding their properties and functions is a critical topic for pre-med students who are preparing for the MCAT.
In this guide, we'll cover everything you need to know about the 20 essential amino acids for the MCAT, including their one-letter and three-letter codes, their categories, and their unique properties.
Non-polar Amino Acids
The first category of amino acids we'll discuss is the nonpolar amino acids. There are ten amino acids in this category, and they are characterized by their hydrophobic nature. These amino acids are often found buried within the interior of proteins, away from water molecules.
Glycine (Gly/G) is the smallest amino acid and has a hydrogen atom as its side chain. Alanine (Ala) has a methyl group as its side chain. Valine (Val/V), leucine (Leu/L), and isoleucine (Ile/I) all have branched side chains, which make them important when it comes to protein structure. Methionine (Met) has a sulfur-containing side chain and is important for protein initiation. Phenylalanine (Phe/F) and tryptophan (Trp/W) are aromatic amino acids with aromatic rings in their side chains. Proline (Pro/P) has a cyclic structure that makes it unique among amino acids. Tyrosine (Tyr/Y) is an aromatic amino acid with a hydroxyl group in its side chain.
Polar Amino Acids
The next category of amino acids is the polar amino acids. These amino acids have hydrophilic properties, which means they are soluble in water. They are often found on the surface of proteins, where they can form hydrogen bonds with water molecules.
Serine (Ser/S), threonine (Thr/T), and cysteine (Cys/C) are all polar amino acids. Cysteine is unique because it contains a thiol group in its side chain, which can form disulfide bonds with other cysteine residues to stabilize protein structure. Asparagine (Asn/N) and glutamine (Gln/Q) are also polar amino acids, and they both contain amide groups in their side chains.
Basic Amino Acids
The next category of amino acids is the basic amino acids. These amino acids have a positive charge at physiological pH and are often involved in ionic interactions with other molecules.
Lysine (Lys/K), arginine (Arg/R), and histidine (His/H) are all basic amino acids. Histidine is unique because it has a side chain with a pKa value close to physiological pH, which allows it to act as a buffer in biological systems.
Acidic Amino Acids
The final category of amino acids is the acidic amino acids. These amino acids have a negative charge at physiological pH and are often involved in ionic interactions with other molecules.
Aspartic acid (Asp/D) and glutamic acid (Glu/E) are the two acidic amino acids. They are often involved in enzyme catalysis and protein-protein interactions.
Summary of Amino Acids for the MCAT
Understanding the properties and functions of the 20 essential amino acids is critical for pre-med students who are preparing for the MCAT. By categorizing the amino acids based on their chemical properties, you can better understand their unique characteristics and how they contribute to the structure and function of proteins.
We hope this guide has helped you better understand the essential amino acids for the MCAT. Good luck with your studies!
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