MCQs

Apoptosis is a highly regulated programmed cell death mechanism central to animal development, tissue homeostasis, and defense.

The middle lamella is rich in pectin salts (calcium and magnesium pectates), which cross-link to form a sticky, cementing extracellular layer.

Without an external wall to anchor its shape, an animal cell losing water collapses completely, shriveling into a wrinkled, crenated morphology.

Plant cells lack discrete centrioles but possess diffuse, membrane-associated MTOCs that organize the cytoskeletal tracking networks.

The thylakoid membranes inside chloroplasts house the photosystems, electron transport chains, and ATP synthase machinery needed for light harvesting.

The rigid plant cell wall serves as a physical barrier that prevents the invagination of the plasma membrane required for endocytosis.

Chromoplasts contain lipid-soluble carotenoids and develop from chloroplasts or leukoplasts, serving to attract pollinators and seed dispersers.

Microfilaments made of actin interact with myosin motor proteins to generate the mechanical constricting force required for the cleavage furrow.

Pectins are branched, hydrophilic polysaccharides that bind water and calcium ions, creating a flexible, hydrated gel matrix in primary walls.

Proteins and lipids are glycosylated in the rough ER lumen and sorted in the Golgi complex before being exported to form the animal glycocalyx.

The cross-linked network of cellulose microfibrils embedded in a matrix of pectin and hemicellulose provides massive tensile resistance against lysis.

Plant Golgi bodies exist as multiple disconnected stacks called dictyosomes distributed throughout the cytoplasm, rather than a single large complex.

Glyoxysomes are temporary, specialized plant peroxisomes that play an essential role in transforming stored seed lipids into transportable sugars.

Plasmolysis occurs when an external hypertonic solution draws water out of the central vacuole, causing the internal protoplast to collapse.

Water enters the central vacuole, pushing the protoplast against the tough cell wall; this builds turgor pressure, keeping the plant upright.

Lacking a rigid cell wall to resist hydrostatic pressure, animal cells absorb water via osmosis until the plasma membrane ruptures.

Animal cells incorporate cholesterol into their membranes to regulate fluidity across temperatures; plants use alternative sterols (phytosterols).

The middle lamella acts as a cellular glue between neighboring plant cells, composed primarily of sticky sticky pectin compounds.

Lignin is a complex, non-carbohydrate aromatic polymer deposited in secondary plant cell walls, rendering them woody, waterproof, and rigid.