Daily Olympiad: Biology - Cell Structure Function [20260519]

Solution

Correct: C

The nucleolus is a structure within the nucleus where ribosomal RNA is synthesized, which is part of ribosome assembly in eukaryotic cells. Prokaryotes lack a nucleolus but have ribosomes for protein synthesis.

Solution

Correct: B

Cyclin-dependent kinases (CDKs) phosphorylate and degrade proteins that maintain the nuclear envelope structure, enabling its disassembly during prophase. Microtubules aid in spindle formation; nuclear pores facilitate transport but not disassembly.

Solution

Correct: A

Mitochondria have a double membrane and their own DNA (mtDNA), consistent with the endosymbiotic theory. They are the primary site of ATP production via oxidative phosphorylation. Other organelles lack both DNA and double membranes.

Solution

Correct: C

Endocytosis requires the fluidity of the phospholipid bilayer to form vesicles by invagination. While proteins like receptors may trigger the process, the structural flexibility of the bilayer is fundamental. Cholesterol modulates fluidity but is not the primary driver.

Solution

Correct: B

Centrioles have a 9+0 arrangement of microtubules, while cilia and flagella have a 9+2 pattern. The 9+0 pattern refers to nine microtubule triplets arranged in a ring without a central pair.

Solution

Correct: D

Both plant central vacuoles and animal contractile vacuoles regulate osmotic balance. Turgor pressure depends on water influx driven by solute gradients, similar to how contractile vacuoles maintain osmotic equilibrium in protists.

Solution

Correct: B

The ATP synthase enzyme complex is embedded in the inner mitochondrial membrane, using the proton gradient generated by the electron transport chain across this membrane to synthesize ATP.

Solution

Correct: B

The smooth endoplasmic reticulum synthesizes lipids and contains enzymes to metabolize drugs and toxins. The rough ER is involved in protein synthesis due to ribosome-studded surfaces.