Q.74 In humans, the key stages in the life cycle of malarial parasites occur in
(A) red blood cells and the liver
(B) red blood cells and platelets
(C) red blood cells and the pancreas
(D) red blood cells and the gut
The correct answer is (A) red blood cells and the liver.
This multiple-choice question tests knowledge of the Plasmodium life cycle in humans, a key topic in parasitology for exams like CSIR NET Life Sciences.
Option Analysis
Option (A) red blood cells and the liver
Sporozoites from an infected mosquito reach the liver, infecting hepatocytes for exo-erythrocytic schizogony, producing merozoites that enter the blood. These merozoites invade red blood cells for erythrocytic schizogony, causing symptoms through cycles of RBC rupture. This matches the primary human stages exactly.
Option (B) red blood cells and platelets
Red blood cells host the erythrocytic stage, but platelets are not a replication site. Platelets interact with infected RBCs, sometimes killing parasites or contributing to thrombocytopenia, yet no key developmental stages occur there.
Option (C) red blood cells and the pancreas
Pancreas involvement is absent from the core cycle; rare complications like pancreatitis arise indirectly from severe infection or cytoadherence, not parasite replication.
Option (D) red blood cells and the gut
The gut hosts no stages in humans; sexual reproduction (gametocytes) occurs in the mosquito’s gut after ingestion.
The life cycle of malarial parasites in humans begins with sporozoites injected by Anopheles mosquitoes, targeting the liver and red blood cells as key sites. This complex Plasmodium falciparum or vivax cycle drives symptoms and transmission, vital for biology exams.
Liver Stage (Exo-Erythrocytic)
Sporozoites invade liver hepatocytes, multiplying into schizonts over 6-15 days without symptoms. Schizont rupture releases merozoites into blood; in P. vivax/P. ovale, hypnozoites cause relapses.
Red Blood Cell Stage (Erythrocytic)
Merozoites enter red blood cells, developing through ring, trophozoite, and schizont forms over 48-72 hours. RBC burst releases more merozoites and gametocytes, causing fever cycles and disease.
Transmission Cycle
Gametocytes, taken by mosquitoes, complete sexual stages in the insect gut, producing sporozoites. No human gut, pancreas, or platelet replication occurs.
