Practice Questions

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.

Amyloplasts are a specific type of leukoplast that converts glucose into starch grains, storing them in roots, tubers, and seeds.

Proposed by Singer and Nicolson, the fluid mosaic model describes the membrane as a fluid phospholipid bilayer embedded with proteins.