MCQs

Vinculin helps anchor internal actin microfilaments to transmembrane integrins, a structural link required for cell-matrix adhesion and motility.

Expansins disrupt the non-covalent links between cellulose and hemicellulose, allowing turgor pressure to expand the primary cell wall.

Mitochondria contain their own circular genome and ribosomes; mutations in their tRNA disrupt internal protein translation and ATP synthesis.

Pumping protons into the central vacuole lowers its internal pH, creating an acidic environment that powers lysosome-like digestive enzymes.

Cellulase breaks down the cellulose microfibrils, and pectinase dissolves the middle lamella, releasing wall-free protoplasts.

Clathrin is required to structuralize and coat invaginating pits during endocytosis; its absence blocks the internalization of specific ligands.

Inhibiting actin prevents the assembly of the contractile ring, blocking cleavage furrow formation and leaving the cell with two nuclei.

Without functional cellulose synthase complexes, the cell cannot build a primary cell wall, causing expanding cells to burst under turgor pressure.

Catalase is a tetrameric protein enzyme containing four heme groups, optimized to break down hydrogen peroxide into water and oxygen.

The branched sugar chains of the glycocalyx act as molecular tags, enabling the immune system to recognize self cells and coordinate interactions.

Integrins are transmembrane receptor proteins that link the intracellular cytoskeleton to the extracellular matrix, facilitating cell signaling.

The plant cell's protoplast shrinks inward while its rigid wall maintains the outer cell shape; the wall-less animal cell shrivels up completely.

Mitochondria harvest chemical energy from food molecules via cellular respiration, producing ATP to power energy-dependent cell processes.

The nuclear lamina is an interlaced protein mesh made of lamins that supports the nuclear envelope and organizes internal chromatin.

The rough ER is studded with active ribosomes, serving as the primary site for translating and folding proteins destined for membranes or export.

Pits are thin depressions in the secondary wall where only the primary wall and middle lamella remain, allowing water to pass between cells.

The cytoskeleton is a dynamic network of microfilaments, intermediate filaments, and microtubules that governs cell shape and movement.

The stroma contains the soluble enzymes (such as RuBisCO) required to fix carbon dioxide into sugars during the Calvin cycle.

Polar molecules cannot pass through the hydrophobic lipid core directly; they require channel or carrier proteins to cross without using energy.