Problem 84 - Objective Biology for NEET

Question

Lysozyme (a) Anti-viral agent (b) Anti-bacterial agent (c) Acts on lipid (d) Acts on carbohydrates

Step-by-Step Solution

Answer

(a) Incorrect, lysozyme is not specifically an anti-viral agent. (b) Correct, lysozyme is an anti-bacterial agent. (c) Incorrect, lysozyme does not act on lipids. (d) Correct, lysozyme acts on carbohydrates in the bacterial cell walls.

Step 1 - Identify Function of Lysozyme

Lysozyme is an enzyme that guards against bacteria. It achieves this by attacking the polysaccharides in the cell walls of the bacteria.

Step 2 - Assess Agents Lysozyme Works Against

As an enzyme that attacks bacteria cell walls, Lysozyme works as an antibacterial agent. It does not attack lipids or act as an antiviral agent. However, it may have some minor indirect antiviral effects.

Step 3 - Determine What Lysozyme Acts On

Since Lysozyme attacks the polysaccharides in the bacterial cell walls, it can be reasoned that it acts on carbohydrates.

Key Concepts

Enzymatic Action of Lysozyme

Lysozyme is a remarkable enzyme found abundantly in secretions like saliva, tears, and mucus, playing a critical role in the body’s immune defense. Its superpower lies in its ability to break down certain carbohydrates called polysaccharides found in the cell walls of bacteria.
Understanding the enzymatic action of lysozyme involves visualizing how it targets the peptidoglycan layer, a vital structural component providing rigidity to bacterial cell walls. Peptidoglycan is made up of sugars and amino acids; lysozyme specifically cleaves the bonds between the sugar molecules, such as N-acetylglucosamine (NAG) and N-acetylmuramic acid (NAM).
By cutting these links, lysozyme effectively weakens the cell wall, leading to osmotic imbalance and ultimately causing the bacteria to burst, a process known as lysis. This action is highly specific and efficient, making lysozyme a first-line defense against bacterial infections.

Antibacterial Agents

Antibacterial agents come in a variety of forms, each designed to combat bacterial infections by either killing bacteria or inhibiting their growth. Lysozyme classifies as a natural antibacterial agent with a specialized function in the disruption of bacterial cell walls.
Unlike antibiotics which are generally broad-spectrum and can affect both harmful and beneficial bacteria, lysozyme exhibits a more targeted approach. Its action is confined to bacteria with a particular type of cell wall composition, primarily gram-positive bacteria due to their thick peptidoglycan layer.
Moreover, considering the concern of antibiotic resistance, lysozyme maintains its efficacy because the enzyme action is less likely to induce resistance compared to conventional antibiotics. This biological tool acts swiftly and locally, commonly within secretions at the entry points of potential infections, providing an essential protective function.

Polysaccharides in Bacteria

Polysaccharides in bacteria serve as critical structural and protective elements, particularly within the cell walls of these microorganisms. The complex, mesh-like structure of peptidoglycan mentioned earlier is primarily made up of polysaccharide chains that confer strength and rigidity.
Two important polysaccharides, N-acetylglucosamine and N-acetylmuramic acid, interlink with short chains of amino acids to form the cell wall's robust framework. While all bacteria have cell walls with polysaccharides, the structure varies significantly between gram-positive and gram-negative bacteria.

Gram-Positive versus Gram-Negative Bacteria

Gram-positive bacteria boast a thicker peptidoglycan layer, making them more susceptible to the action of lysozyme. Conversely, gram-negative bacteria have a thinner peptidoglycan layer and an outer membrane, which makes them less vulnerable to lysozyme but not entirely immune.
This structural differentiation dictates the scope of lysozyme’s effectiveness and exemplifies the importance of polysaccharides to bacterial survival and the potential impact of lysozyme as an antibacterial agent.