Question

Which of the following amino acids have \(\mathrm{R}\) groups that have hydrogen-bonding potential? Ala, Gly, Ser, Phe, Glu, Tyr, Ile, and Thr.

Short answer

Serine, Glutamic Acid, Tyrosine, Threonine.

Step-by-step solution

Understand Hydrogen Bonding

Hydrogen bonding occurs when an electronegative atom such as oxygen or nitrogen is bonded to a hydrogen atom, making the hydrogen partially positive. The presence of hydroxyl \((-OH)\), amino \((-NH_2)\), or carboxyl \((-COOH)\) groups can allow for hydrogen bonding.

Examine Each Amino Acid

Identify the \(\mathrm{R}\) group of each amino acid to determine its hydrogen-bonding potential based on structures:- **Ala (Alanine)**: R group is a methyl group \((-CH_3)\) – no hydrogen bonding.- **Gly (Glycine)**: No side chain, only H – generally doesn't participate in significant hydrogen bonding with side chain.- **Ser (Serine)**: Has an \((-OH)\) in its side chain – can hydrogen bond.- **Phe (Phenylalanine)**: R group is a phenyl ring \((C_6H_5-)\) – no hydrogen bonding.- **Glu (Glutamic Acid)**: Has a carboxyl group \((-COOH)\) – can hydrogen bond.- **Tyr (Tyrosine)**: Has a phenolic \((-OH)\) group – can hydrogen bond.- **Ile (Isoleucine)**: R group is aliphatic – no hydrogen bonding.- **Thr (Threonine)**: Has an \((-OH)\) group – can hydrogen bond.

Determine Which Can Hydrogen Bond

Based on the presence of \((-OH)\) or \((-COOH)\) groups, the amino acids that can participate in hydrogen bonding are Serine, Glutamic Acid, Tyrosine, and Threonine.

Key concepts

Hydrogen Bonding

Hydrogen bonding is an essential type of weak chemical bond found between molecules and within large molecules like proteins and DNA. It occurs when a hydrogen atom is covalently bonded to a more electronegative atom, such as oxygen or nitrogen. This bonding gives the hydrogen a partial positive charge, allowing it to attract nearby electronegative atoms.
In amino acids, hydrogen bonding plays a crucial role in maintaining the structure and function of proteins. The presence of groups such as hydroxyl \((-OH)\), amino \((-NH_2)\), or carboxyl \((-COOH)\) enables these interactions. These bonds are vital for the folding of proteins and stabilizing their secondary and tertiary structures.

• Hydroxyl, amino, and carboxyl groups enable hydrogen bonding.
• Essential for protein shape and stability.

Understanding hydrogen bonding helps in recognizing which amino acids can interact through these bonds, affecting protein behavior and function.

R Groups

The R group, or side chain, is a unique feature to each amino acid, distinguishing one from another. These groups determine the properties and behavior of amino acids, influencing how they interact with each other and with their environment.
The ability of R groups to form hydrogen bonds greatly impacts protein folding and interactions. Only amino acids with specific functional groups within their R group, such as hydroxyl or carboxyl, can participate in hydrogen bonding.
R groups can vary wildly, from non-polar aliphatic to aromatic residues, each contributing differently to protein structure. Students must pay attention to these side chains, as they dictate the hydrogen-bonding potential among amino acids.

• R groups define amino acid properties.
• Participate in hydrogen bonding if they contain electronegative elements.

Serine

Serine is an amino acid known for its capacity to engage in hydrogen bonding due to its polar side chain. Its R group features a hydroxyl \((-OH)\) group, which can serve as both a hydrogen donor and acceptor. This feature makes serine particularly versatile in making connections within proteins or with water molecules.
Serine is often involved in enzymatic activity and cellular signaling due to this ability to form hydrogen bonds. It can stabilize protein structures, aiding in functional conformations. Endowed with an \((-OH)\) group, the hydrogen bonding ability of serine makes it a pivotal part of many biochemical processes.

• Has a hydroxyl \((-OH)\) group in its R group.
• Can donate and accept hydrogen bonds.

Glutamic Acid

Glutamic acid is notable for its ionizable side chain, the carboxyl group \((-COOH)\), that facilitates hydrogen bonding. This feature not only lends itself to multiple bonding opportunities but also contributes to the acid's reactivity and role in protein structure.
As a key player in metabolism and neurotransmission, glutamic acid's capacity to participate in hydrogen bonding makes it crucial in various biochemical pathways. Its side chain can form hydrogen bonds with appropriate acceptors, playing an essential role in stabilizing protein folds and aiding substrate binding in enzymes.

• Contains a carboxyl \((-COOH)\) group.
• Prominent in metabolic and neurological functions.

Tyrosine

Tyrosine is an amino acid characterized by its aromatic side chain containing a phenolic \((-OH)\) group. This group allows tyrosine to form hydrogen bonds, which is important for its function in proteins.Tyrosine's ability to engage in hydrogen bonding is crucial in signal transduction and catalysis. The phenolic \((-OH)\) permits it to engage in robust interactions, contributing to protein stability and activity. This property makes it a valuable component in enzymatic reactions and structural situations requiring specificity and stability.

• Has a phenolic \((-OH)\) group.
• Involved in signal transduction and enzyme activity.

Threonine

Threonine, like serine, possesses a hydroxyl \((-OH)\) group in its R chain, enabling it to actively participate in hydrogen bonding. This property makes threonine an important residue in proteins, particularly those with roles in catalytic and regulatory functions.The presence of its \((-OH)\) group means threonine is usually found in active sites of enzymes and involved in important post-translational modifications. It is also a critical part of protein phosphorylation, affecting protein function and signaling pathways.

• Contains a hydroxyl \((-OH)\) group.
• Involved in enzyme activity and protein modifications.