Question

Name the organic functional groups in the side chains of the following amino acids. \(\begin{array}{ll}{\text { a. glutamine }} & {\text { c. glutamic acid }} \\\ {\text { b. serine }} & {\text { d. lysine }}\end{array}\)

Short answer

a. Glutamine: Amide b. Serine: Hydroxyl c. Glutamic acid: Carboxyl d. Lysine: Amine

Step-by-step solution

Know the structures of the given amino acids

First, we should know the structure of each amino acid. Below are the structures and side chains for each amino acid: a. Glutamine: HOOC–CH(NH2)–CH2–CH2–CONH2 (side chain: –CH2–CH2–CONH2) b. Serine: HOOC–CH(NH2)–CH2–OH (side chain: –CH2–OH) c. Glutamic acid: HOOC–CH(NH2)–CH2–CH2–COOH (side chain: –CH2–CH2–COOH) d. Lysine: HOOC–CH(NH2)–(CH2)4–NH2 (side chain: –(CH2)4–NH2

Identify the functional groups in the side chains

Now, let's find out the functional groups in the side chains of these amino acids: a. Glutamine: The side chain has the functional group –CONH2, which is an amide group. b. Serine: The side chain has the functional group –OH, which is a hydroxyl group. c. Glutamic acid: The side chain has the functional group –COOH, which is a carboxyl group. d. Lysine: The side chain has the functional group –NH2, which is an amine group.

Write the answers

Finally, let's list the identified functional groups of each amino acid's side chains: a. Glutamine: Amide b. Serine: Hydroxyl c. Glutamic acid: Carboxyl d. Lysine: Amine

Key concepts

Organic Chemistry and Functional Groups

In organic chemistry, molecules are defined by their functional groups, which are specific groupings of atoms within molecules that determine how these molecules will react chemically. Functional groups are pivotal because they define the characteristics and properties, such as solubility, boiling point, polarity, and reactivity, of the organic compounds they comprise.

For instance, amino acids, the building blocks of proteins, contain two functional groups systematically; an amino group (-NH2) and a carboxylic acid group (-COOH). These are attached to a central carbon atom. However, it is the variability in their side chains, known as 'R groups', which contains distinct functional groups, that gives different amino acids their unique properties, allowing them to support a vast array of protein structures and functions.

Understanding these functional groups within amino acids is crucial, as they participate in the formation of peptide bonds that create protein chains, interact to form the three-dimensional structure of the protein, and contribute to the chemical reactivity of proteins in various biochemical processes.

Biochemistry of Amino Acids

Biochemistry encompasses the study of the chemical processes within and related to living organisms. Amino acids are central to biochemistry as they are the monomers that make up proteins. Every amino acid consists of a central alpha carbon atom, an amino group (-NH2), a carboxyl group (-COOH), a hydrogen atom, and a distinctive side chain. These side chains are what differentiate each of the 20 standard amino acids found in proteins and can contain various functional groups.

Amino acids are categorized by the characteristics of their side chains, which can be polar, nonpolar, positively or negatively charged. This diversity allows proteins to assume complex three-dimensional shapes and perform a wide range of biological functions. For example, the side chain of serine contains a hydroxyl group which can form hydrogen bonds and is thus polar, while the side chain of lysine contains an amine group, giving it a positive charge under physiological conditions.

The structure of amino acids determines their role and function in the proteins they are part of. For example, amino acids with hydrophilic (water-loving) side chains will often be found on the surface of proteins, interacting with the aqueous environment, whereas hydrophobic (water-fearing) side chains tend to be buried within the core of the protein, away from water.

Protein Structure and Amino Acids

Protein structure is a sophisticated topic in biochemistry that is deeply influenced by the properties of its amino acid constituents. Proteins have four levels of structure: primary, secondary, tertiary, and quaternary.

Primary Structure

Proteins have a unique sequence of amino acids linked by peptide bonds, referred to as the primary structure. The specific order of amino acids defines the protein's shape and function. Variations in the side chain determine the interactions that will occur as the protein folds.

Secondary Structure

Secondary structures, like alpha-helices and beta-pleated sheets, are formed by hydrogen bonds between the backbone of the peptide chain.

Tertiary Structure

Further folding into a three-dimensional shape constitutes the tertiary structure, which is stabilized by various interactions including hydrogen bonds, ionic interactions, and hydrophobic packing. The unique side chains of amino acids play a monumental role here, as they interact in specific ways to help the protein fold and maintain its shape.

Quaternary Structure

Some proteins consist of multiple peptide chains, known as subunits. The arrangement and interactions of these subunits form the quaternary structure.

Understanding protein structure is crucial for grasping how proteins function in biological systems. When we link the types of functional groups present in the amino acids' side chains, such as amides, hydroxyls, carboxyls, and amines, to the broader context of protein structure, we begin to appreciate how these small chemical variations can lead to the dynamic functionality of proteins in living organisms.