Question

The following are the stages of life cycle of {Plasmodium. Arrange the stages in the proper order.
A. The parasites reproduce asexually in RBCs, bursting the cells.
B. The parasites reproduce asexually in liver cells, bursting the cells and releasing into blood.
C. Gametocytes develop in RBCs.
D. Sporozoites reach the liver through the blood.
E. Female mosquito injects sporozoites into humans during bite.
Choose the correct answer from the options given below :}

• A. E, D, B, A, C
• B. C, A, B, D, E
• C. A, B, C, D, E
• D. E, C, D, B, A

Hint:

Logic Tip: Follow the journey geographically: Mosquito bite (Entrance) $\rightarrow$ Bloodstream highway $\rightarrow$ Liver (First base) $\rightarrow$ RBCs (Main battlefield) $\rightarrow$ Gametocytes (Exit waiting room).

Answer 1

The Correct Option is A

Concept:
The life cycle of Plasmodium (the malarial parasite) is complex and digenetic, requiring two hosts: a human (for the asexual phase) and a female Anopheles mosquito (for the sexual phase). Understanding the chronological pathway of infection in the human body is necessary to sequence the events.
Step 1:
The human infection cycle officially begins when an infected female Anopheles mosquito takes a blood meal and injects the infective form of the parasite (sporozoites) along with its saliva into the human bloodstream. First step: E
Step 2:
Once in the bloodstream, the sporozoites do not stay there long. Within about half an hour, they travel through the blood circulation and specifically target and enter the liver cells (hepatocytes). Second step: D
Step 3:
Inside the liver cells, the parasites multiply rapidly through asexual reproduction. They eventually burst the liver cells, releasing thousands of new parasites (merozoites) back into the bloodstream. Third step: B
Step 4:
The released merozoites immediately attack the Red Blood Cells (RBCs). Inside the RBCs, they again reproduce asexually, causing the RBCs to rupture. This bursting releases toxic hemozoin (causing the classic malaria chills/fever) and more parasites to infect new RBCs. Fourth step: A
Step 5:
After a few cycles of asexual reproduction in the blood, some parasites stop dividing and differentiate into sexual stages called gametocytes (male and female) within the RBCs. These will be picked up by the next mosquito to continue the cycle. Fifth step: C
Step 6:
Following the parasite's journey through the human body yields the exact sequence: E $\rightarrow$ D $\rightarrow$ B $\rightarrow$ A $\rightarrow$ C. This perfectly aligns with Option (1).