Problem 100 - Objective Biology for NEET

Question

Which of the following organisms have cell wall made up of cellulose, hemicelluloses, pectins and proteins? (a) Fungi (b) Plants (c) Algae (d) All of these

Step-by-Step Solution

Answer

The correct answer is (b) Plants.

Step 1: Analyze each given organism

First, analyze the cell wall composition of each of the given organisms. For fungi, the cell wall material is primarily composed of chitin. For plants, the cell wall is made up of cellulose, hemicelluloses, pectins and proteins. Algae also possess cell walls, but their composition can vary greatly depending on the group and can be predominantly composed of various different substances such as polysaccharides, glycoproteins, or even silicates, and not necessarily cellulose, hemicelluloses, pectins and proteins. Thus, based on their cell wall composition and materials, identify the organism that fits the criteria.

Step 2: Identify the correct organism

After analyzing each of the stated organisms, it can be identified that plants are the organisms that have cell walls made up of cellulose, hemicelluloses, pectins and proteins.

Key Concepts

Cellulose in Plant Cells

Cellulose is a critical component of plant cell walls, contributing to the plant's overall structure and strength. This polysaccharide is unique to plants and is composed of long chains of glucose molecules linked together. The bonds between these glucose units create microfibrils that are highly resistant to degradation and give the cells tensile strength. Due to its crystalline structure, cellulose can be likened to the steel beams in a building, providing rigidity and support to plant cells. It's important for students to recognize that cellulose is not just a singular entity but works in concert with other wall components like hemicelluloses and pectins, which fill the gaps between cellulose fibers and contribute to the overall matrix, allowing for plant growth and protection against pathogens.

Chitin in Fungi

Chitin serves as the primary structural component in the cell walls of fungi, analogous to cellulose in plants. This rigid, yet somewhat flexible polymer is built from units of N-acetylglucosamine and provides necessary support to the fungal cell. Unlike plant cells, chitin allows for a different kind of growth and flexibility necessary for fungi. Its ability to be broken down and reassembled makes fungal cell walls adaptable and durable in various environments. When studying this, it's essential for learners to understand that the presence of chitin is one of the distinguishing features of fungi, setting them apart from plant and animal kingdoms.

Algae Cell Wall Components

Algae are an incredibly diverse group of organisms, and consequently, their cell wall components can vary significantly. While some algae may contain cellulose, others have walls made of other polysaccharides, glycoproteins, or minerals like calcium carbonate. For example, the cell walls in diatoms, a group of algae, contain a unique component called silica, which forms intricate glass-like structures. Green algae, on the other hand, may contain cell walls with a composition similar to that of higher plants, including cellulose. When discussing algae in educational content, it's necessary to emphasize this diversity and how it reflects the various ecological niches algae occupy.

Structure of Plant Cell Walls

The plant cell wall is not just a static barrier but a dynamic structure that changes throughout the life of the cell. In addition to cellulose, plant cell walls are composed of a heterogeneous mix of hemicelluloses, pectins, and proteins. Hemicelluloses bind to cellulose, creating a network that is embedded within a gel-like matrix of pectins. Pectins are rich in galacturonic acid and play a pivotal role in maintaining wall hydration and cell adhesion. Additionally, structural proteins contribute to the wall's extensibility and defense. Understanding the interplay between these components is crucial for students as it contributes to knowledge about plant growth, development, and responses to environmental stress.