20 Amino Acids Practice Quiz

Amino acids are the building blocks of proteins. They contain an amino group, a carboxyl group, a hydrogen atom, and a unique side chain that determines their properties.

Proteins in humans are built from 20 standard amino acids. These amino acids combine in various sequences to form diverse protein structures.

The R group, also known as the variable side chain, gives each amino acid its unique characteristics. It determines the amino acid's polarity, reactivity, and overall role in protein structure.

A peptide bond is a covalent bond formed between the carboxyl group of one amino acid and the amino group of another. This bond is essential for forming the primary structure of proteins.

An essential amino acid is one that the human body cannot produce on its own. Therefore, it must be acquired through dietary intake.

Cysteine contains a thiol group in its side chain, which can form disulfide bonds with another cysteine residue. These bonds are important for maintaining the protein's tertiary and quaternary structures.

Tryptophan is an essential amino acid that undergoes conversion into serotonin in the body. This process plays a key role in regulating mood and sleep.

There are 9 essential amino acids that the human body cannot synthesize. These amino acids must be obtained through dietary sources to support proper protein synthesis.

Phenylalanine is an essential aromatic amino acid characterized by a benzene ring in its side chain. Its role is critical in protein synthesis and it must be acquired through the diet.

Methionine is an essential amino acid containing sulfur and is universally recognized as the initiator of protein synthesis. Its codon, AUG, signals the start of translation in mRNA.

Leucine has a nonpolar, hydrophobic side chain, making it a key component in the core of protein structures. Its hydrophobic character contributes to the stability of the folded protein.

Glycine is the smallest amino acid and is crucial for the tight packing of collagen's triple helix structure. Its small size allows collagen fibers to adopt a compact and stable configuration.

Lysine has a side chain that carries a positive charge at physiological pH, classifying it as a basic amino acid. This property allows it to form ionic bonds that are critical for protein structure.

Serine contains a hydroxyl group that makes it polar and uncharged, allowing it to form hydrogen bonds with water. This property makes serine prevalent on the surfaces of proteins, enhancing solubility.

Glutamate is a non-essential amino acid that also serves as the principal excitatory neurotransmitter in the brain. Its dual role is vital for both protein synthesis and neural communication.

Proline's unique cyclic structure restricts the rotation around its N-Cα bond, often introducing kinks in alpha helices and affecting overall protein folding. This structural constraint plays a significant role in protein conformation.

Serine is frequently phosphorylated because its side chain contains a hydroxyl group, making it an ideal target for kinases. Phosphorylation of serine residues plays a crucial role in regulating protein activity and signal transduction.

Tyrosine is converted into L-DOPA, which is then transformed into dopamine, an important neurotransmitter. This pathway is integral to the production of catecholamines, including dopamine and norepinephrine.

The zwitterionic form of amino acids presents both positive and negative charges, which enhances their ability to form ionic and hydrogen bonds with water. This interaction significantly increases protein solubility in aqueous environments.

Arginine is typically classified as non-essential; however, in situations such as rapid growth or trauma recovery, the body's demand exceeds its synthetic capacity. Under these conditions, arginine becomes conditionally essential and must be supplied through the diet.