What is an Amoeba?
A type of cell or unicellular organism which has the capability to change its shape, primarily by extending and retracting pseudopodia is known as an Amoeba. An amoeba is found in every major lineage of eukaryotic organisms. An amoeba, also spelled "ameba," is a single-celled eukaryotic organism with no discernible structure that travels using pseudopodia. Pseudopodia, also known as pseudopods, are transient cell extensions that literally mean "false feet." The pseudopodia are used by the cell to move about. Amoebae, not amoebas, is the plural of amoeba. Although the terms "amoeba" and "amoeboid" are frequently used to refer to all protozoa that move with pseudopodia, Amoeba (written in italics and with a capital letter) refers to a specific genus of protozoa, with Amoeba proteus being the best-known species.
When seen under a microscope, an amoeba looks as a colourless, translucent drop of jelly. It lacks a distinct body shape because it constantly alters its shape by creating pseudopodia. As a result, its precise shape, front and posterior ends, and dorsal and ventral surfaces cannot be described. Furthermore, because the shape of an amoeba can alter, its body cannot be separated into two identical halves. Asymmetry is the term for this condition. A fully grown Amoeba can range in size from 1/20 mm to 1 mm. Plasmalema and Protoplasm are the two primary elements of an amoeba's body.
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Mode of Nutrition in Amoeba
Amoeba is a type of protozoa that can be found in freshwater. It feeds on water-borne tiny plants and animals. Holozoic nutrition is the mode of nourishment in amoeba. Phagocytosis is the method through which an amoeba obtains nourishment. Amoeba takes its nutrition through a process called phagocytosis where the entire organism swallows the food it plans on eating up. The mode through which an amoeba engulfs nutrition is known as holozoic nutrition. It leads to the process of ingestion, digestion and egestion of food material. Amoeba doesn’t not have any specialized organs for nutrition. Its entire process is carried through the body surface with the assistance of pseudopodia.
Process of Nutrition in Amoeba
The process by which organisms engulf nutrition inside the body of either solid or liquid food is called the Holozoic Nutrition. The intake of nutrition takes place in the following 5 steps:
Ingestion
Digestion
Absorption
Assimilation
Egestion
Ingestion
The process of taking in the food into the body either by swallowing or absorbing it is called the procedure of Ingestion. Amoeba oozes out the pseudopodia to encircle the food and engulfs it forming a food vacuole. This process is known as phagocytosis.
Digestion
The process of breaking the insoluble and enormous food molecules into soluble and minute molecules is called the process of Digestion. Amoeba digestion occurs intracellularly, within the cell. The food is stored in a food vacuole or stomach vacuole, which is made up of the cell membrane and a tiny amount of cytoplasm. Cytoplasmic motions transport the vacuoles deeper into the cells. They combine with lysosomes, which contain enzymes, in this location. Amylase and proteinase are two enzymes that have been discovered. Sugars, cellulose, and proteins can all be digested by amoeba. In amoeba, the food vacuoles are put deeper into the cell, and with the assistance of the digestive enzymes, the massive insoluble particles are churned down to the simpler molecules.
Absorption
In this process of absorption, the nutrients from the digested food material are absorbed by the cell’s cytoplasm by keeping behind the undigested particles. This process is called diffusion. The excess food is stored as a form of glycogen and lipids.
Assimilation
The process of obtaining energy from the absorbed food molecules is called the procedure of Assimilation. In amoeba, absorbed food molecules are utilized for producing the energy required to hold different life processes within the cell.
Egestion
The process of excretion of undigested food material is called Egestion. In amoeba, this process is administered by rupturing the cell wall to take out the undigested food material from its body. Exocytosis is the process of egestion. Undigested materials are transferred to the back of the amoeba and expelled as food pellets through a transient opening produced at any point on the plasmalemma as the amoeba travels forward.
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Amoeba has a heterotrophic feeding mechanism. The food may be taken in by the entire surface of the amoeba because it is a simple, single-celled organism. A rudimentary form of digestion occurs in food vacuoles instead of a specialized digestive system.
FAQs on Nutrition in Amoeba
1. What is the mode of nutrition in Amoeba?
The mode of nutrition in Amoeba is holozoic. This means it ingests complex solid organic food, which is then broken down into simpler, soluble molecules inside its body. This entire process of 'cell eating' is scientifically known as phagocytosis.
2. What are the five main steps in the process of nutrition in Amoeba?
The process of holozoic nutrition in Amoeba, as per the CBSE syllabus, involves five sequential steps:
Ingestion: The Amoeba surrounds a food particle with its pseudopodia and engulfs it, forming a food vacuole.
Digestion: Digestive enzymes are released into the food vacuole to break down the complex food into simple, absorbable substances.
Absorption: The digested nutrients diffuse from the food vacuole directly into the cytoplasm.
Assimilation: The absorbed nutrients are utilised by the cell for energy production, growth, and repair.
Egestion: The undigested waste materials are moved to the surface of the cell and expelled.
3. What role do pseudopodia play in the nutrition of an Amoeba?
Pseudopodia, or "false feet," are crucial for nutrition in Amoeba. They are temporary extensions of the cell's cytoplasm that perform two key functions: locomotion (moving towards the food source) and ingestion. They extend to encircle a food particle, eventually fusing to form a food vacuole where the food is trapped for digestion.
4. How is food digested inside an Amoeba's cell?
Food digestion in an Amoeba occurs entirely within a temporary structure called the food vacuole. Once the food is ingested, lysosomes, which are organelles containing powerful digestive enzymes, fuse with the food vacuole. These enzymes then break down the complex, insoluble food particles into simple, soluble molecules that can be easily absorbed by the cytoplasm.
5. How does an Amoeba get rid of undigested waste?
An Amoeba expels its undigested waste through a process called egestion. Since it lacks a specialised excretory organ, the food vacuole containing the waste moves towards the cell membrane. The membrane then ruptures at that point, releasing the waste materials out of the cell into the surrounding environment.
6. Why is the mode of nutrition in Amoeba called holozoic and not saprotrophic?
The nutrition in Amoeba is termed holozoic because it involves the ingestion and internal digestion of solid organic matter. This is different from saprotrophic nutrition, where organisms like fungi secrete enzymes externally to digest food before absorbing the nutrients. Amoeba takes the 'whole' food particle inside its body first, which is the defining characteristic of the holozoic mode.
7. How is the process of nutrition in Amoeba different from that in Paramecium?
While both Amoeba and Paramecium are unicellular and have holozoic nutrition, their method of ingestion is different. Amoeba uses temporary pseudopodia to engulf food from any point on its surface. In contrast, Paramecium has a more specialised structure; it uses its hair-like cilia to sweep food particles into a fixed, specific mouth-like opening called the cytostome or oral groove.
8. Does an Amoeba have a specific spot for ingestion or egestion like higher animals?
No, an Amoeba does not have a fixed location for taking in food or removing waste. Unlike higher animals with a mouth and anus, an Amoeba's flexible cell membrane allows it to form pseudopodia to engulf food at any point. Similarly, egestion can occur anywhere along the cell surface where the waste-filled vacuole fuses with the membrane and ruptures.
9. What would happen if the food vacuole in an Amoeba failed to fuse with a lysosome?
If a lysosome did not fuse with the food vacuole, digestion would not occur. Lysosomes contain the essential digestive enzymes required to break down complex food into simple nutrients. Without this fusion, the food inside the vacuole would remain undigested, and the Amoeba would be unable to absorb any nutrients from it, ultimately leading to starvation.
