MCQs

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.

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.

The smooth ER in hepatocytes contains cytochrome P450 enzyme families that chemically modify and detoxify hydrophobic drugs and toxins.

The nucleolus functions as a ribosome manufacturing center, transcribing rRNA and combining it with proteins to form ribosomal subunits.

Tight junctions form a continuous fluid-tight seal between adjacent cell membranes, preventing materials from leaking between cells.

Invaginating the inner mitochondrial membrane into cristae creates a large surface area for housing electron transport chain complexes.

A hypertonic environment draws water out of the animal cell, collapsing its volume and causing the cell membrane to wrinkle and shrivel.