Question

An erample of aromatic amino acid is (a) trrosine (b) phemylalanine (d) Iryptophan (d) all of these.

Short answer

The correct answer is (d) all of these, as tyrosine, phenylalanine, and tryptophan all have aromatic rings in their structures and are considered aromatic amino acids.

Step-by-step solution

Understand the characteristics of aromatic amino acids

Aromatic amino acids are those that contain an aromatic ring structure within their side chain. This group includes amino acids like tyrosine, phenylalanine, and tryptophan.

Identify the aromatic amino acids given in the options

Look at each option and determine if it contains an aromatic ring in its structure. (a) Tyrosine has a phenol ring, (b) Phenylalanine has a benzyl side chain, and (c) Tryptophan has an indole ring, all of which are types of aromatic rings.

Determine the correct answer

Since all the given options have an aromatic ring in their side chain, they are all considered aromatic amino acids. Therefore, the correct answer is (d) all of these.

Key concepts

Tyrosine

Tyrosine is not only one of the 20 standard amino acids used to build proteins in the body, but it also plays a central role in several metabolic processes. Structurally, it contains a phenol ring, which makes it an aromatic amino acid. Its side chain can form hydrogen bonds, which is why it is often found in the active sites of enzymes or participating in signal transduction processes.

Moreover, tyrosine is a precursor to important neurotransmitters like dopamine, norepinephrine, and epinephrine. It's also vital for the synthesis of hormones, including thyroid hormones. Tyrosine's relevance extends to its ability to be phosphorylated, turning into phosphotyrosine, which plays a significant role in cell signaling.

Role in Protein Structure

Within proteins, tyrosine often contributes to the three-dimensional stability of the protein structure due to its ability to engage in stacking interactions with other aromatic side chains.

Phenylalanine

Phenylalanine is another aromatic amino acid with a benzyl side chain. It's a precursor to tyrosine, meaning that the body converts phenylalanine to tyrosine through enzymatic processes. This essential amino acid is not synthesized by the human body and must be obtained from the diet.

Within proteins, phenylalanine contributes to the hydrophobic core, often stabilizing the protein structure through hydrophobic interactions. Its aromatic ring also participates in stacking interactions that are key to maintaining the shape of proteins.

Phenylketonuria (PKU)

A disorder associated with phenylalanine is phenylketonuria (PKU), where the body cannot properly metabolize this amino acid, leading to its accumulation and potential brain damage. It's an example of how crucial amino acid metabolism is for human health.

Tryptophan

Tryptophan stands out among the aromatic amino acids due to its indole ring, making it the largest of the three discussed. It is also an essential amino acid, meaning that it must be ingested as the human body cannot produce it. Tryptophan is a precursor to serotonin, a neurotransmitter that plays a significant role in mood regulation and sleep.

In the context of protein biochemistry, tryptophan's large side chain is involved in various interactions that affect protein folding and function. It can act as a fluorescence probe in studies of protein structure because it naturally fluoresces when exposed to ultraviolet light.

Nutrition and Function

Its presence in dietary proteins is vital, and its levels can influence serotonin production, thus affecting sleep patterns and mood. Tryptophan's importance is underscored by its involvement in multiple metabolic pathways beyond protein synthesis.

Protein Biochemistry

Protein biochemistry is the study of the structure and function of proteins, the workhorses of cells. Proteins are made up of amino acids, which are linked together by peptide bonds to form polypeptide chains. These chains fold into specific three-dimensional structures that determine the protein's function.

Amino acids like tyrosine, phenylalanine, and tryptophan are known as aromatic due to their ring-shaped structures, which absorb ultraviolet light. The interactions between these aromatic rings and their hydrophobicity can significantly influence protein folding and stability.

Protein Functionality and Aromatic Amino Acids

Proteins with these amino acids can interact with other molecules, such as nucleic acids or other proteins, facilitate enzyme reactions, or partake in cellular signaling. The distinctive side chains of these aromatic amino acids are key to their roles, impacting attributes like protein active sites and signaling pathways.

Therefore, understanding these amino acids' chemical properties gives insight into how proteins function and how they can be manipulated for biotechnological or therapeutic purposes.