Question

Difficulty: MediumKingdom Protista: Protozoa and Unicellular Algae

What is the correct sequential order of the process of phagocytosis and intracellular digestion in *Amoeba proteus* from initial contact to waste removal?

  1. 1Extension of pseudopodia around the food particle to form a food cup and enclose it in a food vacuole.
  2. 2Fusion of lysosomal vesicles with the food vacuole to release hydrolytic digestive enzymes.
  3. 3Diffusion of digested, soluble nutrients across the vacuolar membrane into the surrounding cytoplasm.
  4. 4Egestion of indigestible waste through the plasma membrane as the vacuole fuses with the outer surface.

Answer

The correct sequence begins with the extension of pseudopodia around the food particle to enclose it in a vacuole, followed by the fusion of lysosomes to release digestive enzymes, then the diffusion of digested nutrients into the cytoplasm, and ends with the egestion of indigestible waste at the cell surface.
In Amoeba proteus, holozoic nutrition follows five clear physiological phases: ingestion (pseudopodial engulfment), digestion (lysosomal enzyme secretion into the food vacuole), absorption (diffusion of nutrients into cytoplasm), assimilation, and egestion (exocytosis of solid waste). Placing pseudopodial engulfment first, lysosomal fusion second, nutrient diffusion third, and waste elimination last reflects the true sequence.

Step-by-Step Solution

1
Identify the initial phase of food uptake in Amoeba.
Pseudopodia extend around the organism to enclose it within a food vacuole (phagocytosis).
Intracellular digestion requires the food item to first be brought inside the cell bounded by a membrane.
2
Determine how the food material is chemically broken down.
Lysosomes fuse with the food vacuole and discharge hydrolytic enzymes.
Enzymes are required to hydrolyze complex food molecules into simple soluble forms inside the vacuole.
3
Trace the movement of digested products.
Soluble food products diffuse across the vacuolar membrane into the cytoplasm for assimilation.
The cell utilizes digested nutrients by absorbing them into the active cytoplasm.
4
Identify the final disposal step of insoluble materials.
The vacuole containing indigestible residues moves to the cell surface and ruptures to release waste.
Undigested residue cannot remain in the cell and must be eliminated by exocytosis/egestion.

Key Concept

Holozoic Nutrition and Phagocytosis in Sarcodina (Amoeba)
Estimated Time:1m 0s
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