Amoeba is a unicellular organism that obtains nutrition through a process called holozoic nutrition — the same type of nutrition as animals, involving ingestion of solid food, intracellular digestion, and egestion of undigested material. Amoeba feeds on algae, bacteria, and other microscopic organisms in its environment using temporary extensions of its body called pseudopodia ('false feet').
Nutrition in Amoeba = Holozoic (same type as animals)
Food capture by pseudopodia through phagocytosis
5 steps: Ingestion → Digestion → Absorption → Assimilation → Egestion
Food vacuole = membrane sac formed during ingestion
Digestion is intracellular (inside the food vacuole using lysosome enzymes)
Egestion occurs at any point on cell surface (no fixed anus)
Pseudopodia = temporary cytoplasmic extensions used for locomotion AND food capture
Amoeba shows Holozoic nutrition — a type of heterotrophic nutrition in which organisms ingest solid food, digest it internally, and absorb nutrients.
Other types of heterotrophic nutrition (for comparison):
Amoeba is the classic example of holozoic nutrition in unicellular organisms.
Ingestion: Amoeba engulfs food by extending pseudopodia (temporary cytoplasmic projections) around the food particle. The pseudopodia surround and engulf the food, forming a food vacuole (a membrane-bound sac containing food). This process is called phagocytosis ('cell eating').
Digestion: Digestive enzymes from lysosomes are secreted into the food vacuole. Complex food molecules (proteins, carbohydrates, fats) are broken down into simpler, soluble molecules (amino acids, glucose, fatty acids). This is intracellular digestion (inside the cell).
Absorption: Simplified food molecules (nutrients) pass from the food vacuole into the cytoplasm by diffusion. The food vacuole shrinks as nutrients are absorbed.
Assimilation: Absorbed nutrients are used by the cell for energy production (cellular respiration), growth, and repair. They become part of the cell's living matter (protoplasm).
Egestion: Undigested food material is expelled out of the cell at any point on the cell surface, since Amoeba has no fixed anus or excretory organ. The food vacuole fuses with the cell membrane and the contents are expelled.
Pseudopodia (singular: pseudopodium) = 'false feet' — temporary projections of the cytoplasm in Amoeba.
Functions:
Structure: Pseudopodia are formed by the flow of cytoplasm (ectoplasm into endoplasm) in a specific direction. They retract and re-form as needed.
Type: Amoeba's pseudopodia are lobopodia (broad, finger-like).
Amoeba captures food by extending temporary cytoplasmic projections called pseudopodia ('false feet'). The pseudopodia surround and engulf food particles (bacteria, algae) through a process called phagocytosis, forming a food vacuole. Inside the food vacuole, digestive enzymes from lysosomes break down the food.
Nutrition in Amoeba has 5 steps: (1) Ingestion — engulfing food using pseudopodia, forming a food vacuole. (2) Digestion — enzymes in the food vacuole break down food into simpler molecules. (3) Absorption — nutrients diffuse into cytoplasm. (4) Assimilation — nutrients are used for energy and growth. (5) Egestion — undigested waste expelled through cell surface.
A food vacuole is a membrane-bound sac formed inside Amoeba's cell when pseudopodia engulf food through phagocytosis. Digestive enzymes (from lysosomes) are secreted into the food vacuole, where food is broken down. As digestion proceeds, nutrients are absorbed into the cytoplasm and the vacuole shrinks.
Amoeba shows holozoic nutrition — a type of heterotrophic nutrition in which solid food is ingested, digested internally, and undigested material is egested. It is similar to the nutrition of animals. Amoeba is a unicellular example of holozoic nutrition.
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