The walls of xylem cells are lignified (strengthened with a substance called lignin ). This allows the xylem to withstand pressure changes as water moves through the plant.
The cell membrane is flexible because of the presence of oil like substances called phospholipids, which gives it a fluid nature. While as the cell walls are rigid because of the presence of the thick layers of the substances like cellulose in plants, chitin in fungi and peptidoglycon in bacteria.
The cell membrane is in control of what materials go in and out of the cell so the correct answer is 4. Regulates diffusion.
Hope I helped!
Passive transport<span> is a kind of </span>transport<span> by which ions or molecules move along a concentration gradient, which </span>means<span> movement from an area of higher concentration to an area of lower concentration. Examples of passive </span>transport<span>include diffusion, filtration, and osmosis.</span>
