Practice Questions

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.