Question

Which of the following is a heteropolymer? (a) Cellulose (b) Peptidoglycon (c) Starch (d) Glycogen

Short answer

Peptidoglycan is a heteropolymer.

Step-by-step solution

Defining a Heteropolymer

A heteropolymer is a polymer made up of different types of monomer units, as opposed to a homopolymer where only one type of monomer is present. To determine which of the options is a heteropolymer, look at the structure of the polymers mentioned.

Analyzing Each Option

Analyze the structure of the polymers in each option to determine if they consist of different monomers. (a) Cellulose is a homopolymer composed of glucose monomers. (b) Peptidoglycan consists of repeating units of N-acetylglucosamine and N-acetylmuramic acid with attached peptides, making it a heteropolymer. (c) Starch, like cellulose, is composed of glucose monomers, so it is a homopolymer. (d) Glycogen is also composed of glucose units, and therefore, is a homopolymer.

Identifying the Heteropolymer

Given the analysis, peptidoglycan is the only option that is made from multiple types of monomers—sugars and amino acids. Therefore, peptidoglycan is a heteropolymer.

Key concepts

Peptidoglycan Structure

When exploring the complex world of biological structures, one can't help but be intrigued by the peptidoglycan structure. Found predominantly in the cell walls of bacteria, this substance is pivotal for maintaining the cell's shape and protecting it from osmotic pressure. The structure of peptidoglycan is a result of alternating molecules of N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM), linked in chains. Attached to each NAM is a short peptide chain, which can crosslink with other peptides to form a 3D mesh-like structure.

This unique composition marks peptidoglycan as a heteropolymer due to the presence of different types of monomers: sugars and amino acids. This structural complexity is critical for the rigidity and strength of the bacterial cell wall, making peptidoglycan an attractive target for antibiotics, such as penicillin, which disrupts its synthesis and thus weakens the bacterial defenses.

Polymer Classification

Delving into the classification of polymers, it's essential to comprehend the variety present in their structures. Polymers are large molecules made up of repeating subunits called monomers. The classification of polymers into homopolymers and heteropolymers depends on the uniformity of these monomers.

A homopolymer consists of identical monomer units repeated throughout the molecule. Examples include cellulose and glycogen—both constituted by glucose monomers. On the other hand, a heteropolymer comprises two or more different kinds of monomers. Peptidoglycan is an excellent example of a heteropolymer with its varied units of amino acids and sugars. This classification is not a mere formality but a reflection of the polymer's properties and functionalities; the variety of monomers in heteropolymers contributes to the complexity and potential for diverse functions in biological organisms.

Biological Macromolecules

Biological macromolecules are the cornerstone of life, composing the essential building blocks of cells and organisms. These giant molecules can be categorized into four main types: carbohydrates, proteins, lipids, and nucleic acids. Each serves a crucial role, from providing energy and structural support to carrying genetic information.

The peptidoglycan layer we discussed earlier is a composite of carbohydrates and proteins, showcasing the interaction between different macromolecule types to perform a specific biological function. Understanding the roles and interactions of these macromolecules is foundational to grasping biochemistry and molecular biology. Their diversity and complexity enable the multitude of forms and functions necessary for life as we know it.