MCQs

Proteinoplasts are specialized, non-pigmented leukoplasts optimized to store high-density protein reserves inside seeds and kernels.

The smooth ER houses the key enzyme pathways required for lipid metabolism, cholesterol processing, and steroid hormone biosynthesis.

When water loss exceeds intake, turgor pressure drops to zero, causing the soft tissues of the plant to lose structural rigidity and wilt.

While cellulose is built by plasma membrane enzymes, non-cellulose wall polysaccharides are synthesized in the Golgi and shipped out via vesicles.

Six connexin proteins assemble to form a hemichannel called a connexon; when aligned with a neighbor, it creates a functional gap junction.

The phragmoplast is an array of microtubules and filaments that forms during late mitosis, guiding Golgi vesicles to the cell plate site.

Cholesterol inserts its rigid steroid ring core between phospholipid tails, stabilizing the membrane and regulating fluid properties.

Cutin is a complex macromolecular lipid polymer that coats the outer surfaces of land plants, reducing non-stomatal transpirational water loss.

The central vacuole maintains an acidic internal pH and houses a variety of hydrolytic enzymes to break down and recycle macromolecules.

Animal cells rely on an intricate network of specialized junctional complexes to bind cells structurally and coordinate tissue-wide communication.

Intermediate filaments (like keratins, lamins, and vimentin) possess high tensile strength, protecting animal cells from stretching and tearing.

Peroxisomes host amino acid and fatty acid oxidation reactions that generate hazardous H2​O2​, which is immediately neutralized by catalase.

Hydrostatic turgor pressure pushes cells tightly against one another, providing mechanical structural support to non-woody plant organs.

Fungi utilize chitin (a polymer of N-acetylglucosamine) for structural support, while plants rely on cellulose.

The interlaced arrangement of cellulose microfibrils leaves large physical pores that allow water and small solutes to diffuse freely.

The spindle apparatus, built from tubulin heterodimers, attaches to kinetochores to pull chromosomes to opposite poles in all eukaryotic cells.

The secondary wall is thick and contains dense cellulose and lignin, providing structural reinforcement to mature, non-growing plant tissues.

The primary cell wall is laid down by expanding cells; it is thin, extensible, and flexible, accommodating cell growth and elongation.

Elaioplasts are specialized, non-pigmented plastids dedicated to storing lipids and essential fatty oils inside plant seeds or leaves.