AP BIOLOGY

Detailed explanation-1: -The lignified cell wall has pits. Lignin makes the cell wall impermeable and doesn’t allow substances to pass through it. As a result, heavily lignified cells are without living cytoplasm. Lignin is basically deposited in tracheids, vessels, fibres of xylem and phloem and sclerenchyma.

Detailed explanation-2: -The cellulose molecules provide tensile strength to the primary cell wall. Each molecule consists of a linear chain of at least 500 glucose residues that are covalently linked to one another to form a ribbonlike structure, which is stabilized by hydrogen bonds within the chain (Figure 19-70).

Detailed explanation-3: -Lignin is a crucial organic polymer which is abundant in cell walls of some specific cells. As they are dead, they cement together and anchor the cellulose fibres of the cell wall giving it a rigid and woody structure. It shows hydrophobic properties, which means they do not mix with water and are impermeable.

Detailed explanation-4: -Background Lignin is a polyphenolic polymer that strengthens and waterproofs the cell wall of specialized plant cell types.

Detailed explanation-5: -Lignin is one of the main components of plant cell wall and it is a natural phenolic polymer with high molecular weight, complex composition and structure.