Which organelle is known as the 'powerhouse of the cell'? MCQ with Answer and Explanation

Explanation:
Transcription is the first step of gene expression, where a specific segment of DNA is copied into RNA (specifically mRNA) by the enzyme RNA polymerase. This occurs in the nucleus of eukaryotes. The mRNA then carries the genetic code from the DNA to the ribosomes in the cytoplasm for translation (protein synthesis).

Explanation:
A mid-cycle surge in luteinizing hormone (LH) triggers the final maturation and release of the secondary oocyte from the Graafian follicle (ovulation). FSH stimulates follicle growth, estrogen proliferates uterine lining, progesterone maintains it.

Explanation:
During the light reactions of photosynthesis, photolysis of water occurs at photosystem II, splitting water into protons, electrons, and molecular oxygen. The oxygen comes from water, not CO₂. This was demonstrated by using isotopically labeled oxygen (H₂O¹⁸). Glucose is formed in the Calvin cycle. Chlorophyll absorbs light but does not provide oxygen. The overall equation: 6CO₂ + 12H₂O → C₆H₁₂O₆ + 6O₂ + 6H₂O.