Which structure is common to both prokaryotic and eukaryotic cells?
A. Golgi apparatus
B. Mitochondria
C. Ribosomes
D. Nuclear membrane
Answer: Option C
Solution (By JKSSB Mock Tests)
Ribosomes are the only organelles common to both prokaryotes and eukaryotes, though sizes differ: 70S in prokaryotes, 80S in eukaryotes. Nuclear membrane, mitochondria, and Golgi are absent in prokaryotes. Ribosomes are the site of protein synthesis. This commonality supports the universal role of protein synthesis in all life forms. Mycoplasma, the smallest prokaryote, also has ribosomes.
Explanation:
Zinc is a micronutrient that acts as a cofactor for tryptophan synthetase, an enzyme involved in the biosynthesis of the auxin indole-3-acetic acid (IAA) from tryptophan. Zinc deficiency causes stunted growth and 'little leaf' disease. Iron is for chlorophyll synthesis, copper for enzymes, manganese for photosystem II.
Explanation:
Malaria is a life-threatening mosquito-borne infectious disease caused by protozoan parasites of the genus Plasmodium. Four species infect humans: P. falciparum (most severe), P. vivax, P. ovale, and P. malariae. The parasite undergoes a complex life cycle in both humans (asexual phase) and the female Anopheles mosquito (sexual phase).
Explanation:
The loop of Henle, especially the descending limb (permeable to water) and ascending limb (impermeable, active salt transport), creates an osmotic gradient in the medulla. This countercurrent multiplier system enables the kidney to produce concentrated or dilute urine depending on hydration status. ADH acts on the collecting duct to utilize this gradient.
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