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

Step 1 : Understanding the Question:
The question asks to sequence the life cycle of the malarial parasite {Plasmodium} as it occurs within the human host. This requires knowledge of the exo-erythrocytic and erythrocytic phases of the infection.
Step 2 : Key Formulas and Approach:
The malarial life cycle in humans is asexual and follows a strict anatomical route:
Skin (Inoculation) $\rightarrow$ Blood (Migration) $\rightarrow$ Liver (Pre-erythrocytic phase) $\rightarrow$ Red Blood Cells (Erythrocytic phase) $\rightarrow$ Gametogenesis.
Step 3 : Detailed Explanation:

Infection Stage (E): The cycle starts when an infected female Anopheles mosquito bites a human, injecting the infectious form of the parasite, known as sporozoites, along with its saliva into the bloodstream.

Targeting the Liver (D): Within minutes, these sporozoites travel through the blood circulation to reach the liver cells (hepatocytes), which are their primary target for initial reproduction.

Liver Multiplication (B): Inside the liver, the parasites reproduce asexually (schizogony). They multiply until they burst the liver cells, releasing thousands of merozoites back into the blood.

RBC Invasion (A): The released merozoites then invade the erythrocytes. They reproduce asexually in RBCs, leading to their rhythmic bursting, which causes the characteristic symptoms of fever and chills.

Sexual Stage Formation (C): After some cycles of asexual reproduction in the blood, some parasites differentiate into the sexual forms, the male and female gametocytes, which develop within the RBCs.

Step 4 : Final Answer:
The correct chronological order of the life cycle events in the human host is E $\rightarrow$ D $\rightarrow$ B $\rightarrow$ A $\rightarrow$ C. This sequence matches the first provided option.