Which of the following is an example of active transport across the cell membrane? MCQ with Answer and Explanation

Explanation:
Secretin is a peptide hormone released by the S cells of the duodenal mucosa in response to acidic chyme entering from the stomach. Its primary action is to stimulate the pancreatic ductal cells to secrete a large volume of water and bicarbonate ions. This alkaline juice neutralizes the acidic chyme, providing the optimal pH for pancreatic digestive enzymes to function. Cholecystokinin (CCK) stimulates enzyme secretion.

Explanation:
Kala-azar, also known as visceral leishmaniasis, is a severe systemic disease caused by the protozoan parasite Leishmania donovani. The disease is transmitted to humans through the bite of an infected female Phlebotomus sandfly (in the Old World) or Lutzomyia sandfly (in the New World). The sandfly injects the infective promastigote stage of the parasite into the skin during a blood meal. Anopheles transmits malaria, Aedes transmits dengue and yellow fever, and Culex transmits filariasis.

Explanation:
Centrioles are cylindrical structures composed of nine evenly spaced peripheral fibrils of tubulin, arranged in a 9+0 pattern. Each fibril is a triplet of microtubules. The central part is non-branched and lacks microtubules. Centrioles are involved in forming the spindle apparatus in animal cells and basal bodies of cilia and flagella.