How Does Amoeba Obtain and Digest Its Food?
Amoeba is a unicellular protozoa whose digestion takes place in the food vacuole. The food ingested is engulfed by pseudopodia through the process of phagocytosis. The food vacuoles then fuse with lysosomes to form phagolysosomes that contain the enzymes essential for breaking down food particles.
Modes of Nutrition
Nutrients are reported to provide the energy required for carrying out our vital functions. Broadly, the nutrition in living organisms can be classified into two types, autotrophic and heterotrophic.
In the autotrophic mode of nutrition, the organisms utilize simple inorganic molecules like water and carbon dioxide to synthesize food with the air of light and chlorophyll on their own. Plants, algae, and cyanobacteria can synthesize their own food.
In the case of heterotrophic nutrition, organisms depend on others for their nutrition as they are incapable of synthesizing their food, unlike plants. Fungi and animals, including humans, are heterotrophs, which can again be classified into different groups depending on the type of their environment and adaptations.
Those who eat plants are called herbivores, and those feeding on animals are called carnivores. Few organisms feed on both, and they are called omnivores. Heterotrophs are again classified into 3 groups based on their mode of nutrition. First is the parasites that include leeches, ticks, Saprophytes (e.g. mushrooms), and Holozoic (e.g. humans, dogs) are the other groups.
Digestion in Amoeba
Amoeba is a eukaryotic organism that is classified as protozoa. All the protozoans have the special characteristics of living inside the host as parasites; hence they are also known as primitive relatives of animals.
Holozoic nutrition is the mode of nutrition in these organisms. The process of digestion in amoeba involves ingestion, digestion, absorption, assimilation, and egestion. Amoeba being a single-celled organism is reported to have intracellular digestion, which is facilitated by digestive enzymes that break down the large insoluble particles into simple ones. The finger-like projections called pseudopodia help in this process. The pseudopodia extend and engulf the food particle.
Amoeba digests their food in the food vacuole. The food vacuole is formed due to ingestion and its combination with lysosomes. The digested and absorbed food provides energy, and the excess food is stored as glycogen. The amoeba contains membrane-bound organelles such as lysosomes that contain hydrolytic enzymes like proteases, nucleases, and lipases. After the process of digestion, the enzymes are egested out. The process of engulfing liquid in amoeba is called pinocytosis.
Amoeba Diagram
Process of Nutrition in Amoeba
Nutrition in an Amoeba takes place through a process also known as phagocytosis. In this process, the entire amoeba engulfs the food/bacteria. It shows heterotrophic nutrition, characterized by the internalization of liquids or solid food. Nutrition involves the following steps. ingestion, digestion, absorption, assimilation and egestion of food. The body surface of the amoeba takes part in the process as they do not have any specialized organs for nutrition.
The first step is ingestion which is the process of engulfing food by swallowing inside the body through the process of phagocytosis. Food vacuoles are formed as a result of the internalization of food. The next step is digestion, where the mechanical and chemical breakdown of the ingested food takes place with the aid of digestive enzymes.
Absorption is the process of absorption of nutrients from digested food. The excess food is later stored as glycogen or lipids for future use. Assimilation is the process of oxidation of food to gain the energy required for survival. Lastly, egestion takes place where the undigested food is excreted. The pseudopods or false feet are the cytoplasmic extensions which help the amoeba to engulf food. The amoeba has no mouth or anus, so digestion occurs through the cell surface.
Nutrition in Amoeba Diagram
What is Pseudopodia?
Pseudopodia or false feet are temporary projections of the cell membrane of a eukaryotic cell. Movement with pseudopodia is the most primitive form of movement that occurs in amoeba. Amoeba, which is a single-celled organism, is characterised by the property of forming arm-like protrusions that have the ability to change their shape constantly. The shape of the amoeba is irregular due to the presence of these pseudopodia.
Interesting Facts
Amoeba appears like blobs of jelly-like substance, and it does not have any fixed body shape.
Amoeba can create body extensions called pseudopodia which help in digestion and locomotion.
Key Features
Amoeba belongs to protozoans, and it is responsible for causing amoebic dysentery.
The process of absorbing liquids by amoeba is known as pinocytosis.
Contractile vacuoles are accountable for osmoregulation, and this prevents the cell from bursting.
The food vacuole is where digestion occurs, as the digestive enzymes are present here.
FAQs on Feeding and Digestion in Amoeba: A Complete Guide
1. What are the main steps in the process of feeding and digestion in Amoeba?
The process of feeding and digestion in Amoeba, known as holozoic nutrition, is completed in five sequential steps:
- Ingestion: The Amoeba surrounds a food particle with its finger-like projections called pseudopodia, engulfing it to form a food vacuole.
- Digestion: Inside the food vacuole, digestive enzymes break down the complex food into simpler, soluble molecules.
- Absorption: The digested nutrients diffuse from the food vacuole directly into the cytoplasm.
- Assimilation: The absorbed nutrients are used by the cell for growth, energy, and repair.
- Egestion: The undigested waste material is moved to the cell surface and expelled by the rupture of the cell membrane.
2. What structure does an Amoeba use to capture its food?
An Amoeba uses temporary, finger-like projections of its cytoplasm called pseudopodia (meaning 'false feet') to capture food. These structures extend and flow around the food particle, eventually engulfing it. This process of engulfing solid food is known as phagocytosis.
3. What is a food vacuole and what is its importance in Amoeba's digestion?
A food vacuole is a temporary, membrane-bound sac that forms within the Amoeba's cytoplasm after it engulfs a food particle. Its primary importance is that it acts as a temporary 'stomach'. It keeps the food contained while lysosomes fuse with it to release digestive enzymes, ensuring that the complex food is broken down efficiently without harming the rest of the cell.
4. How are digested nutrients absorbed and used by the Amoeba?
After digestion inside the food vacuole, the simple and soluble nutrients pass through the vacuole's membrane and enter the surrounding cytoplasm. This process is called absorption. Once absorbed, the cell utilises these nutrients for various life processes like producing energy, growing, and repairing cellular parts. This utilisation process is known as assimilation.
5. How does an Amoeba get rid of its undigested waste material?
An Amoeba gets rid of undigested waste through a process called egestion. The food vacuole, now containing only waste materials, moves towards the edge of the cell. The cell membrane then ruptures at that point, and the waste is expelled outside the body. The membrane then heals itself.
6. Why is the mode of nutrition in Amoeba referred to as holozoic?
Nutrition in Amoeba is called holozoic nutrition because it involves the ingestion of solid organic food particles from the environment. The term 'holozoic' describes organisms that take in complex food and break it down internally. Amoeba exhibits all the key stages of this process: ingestion, digestion, absorption, assimilation, and egestion, which is characteristic of holozoic organisms, including more complex animals like humans.
7. How is digestion in a single-celled Amoeba different from digestion in a complex animal like a human?
The primary difference lies in the location and complexity of the process. In Amoeba, digestion is intracellular, meaning it occurs inside the cell within a food vacuole. It does not have any specialised digestive organs. In contrast, humans have extracellular digestion, which occurs outside the cells in a specialised and complex alimentary canal (digestive tract) involving multiple organs like the stomach and intestines, along with various digestive glands.
8. What is the importance of the cell membrane's flexibility in Amoeba's feeding process?
The flexibility of the cell membrane is crucial for Amoeba's survival. This property allows it to constantly change its shape to form pseudopodia, which are essential for both moving and engulfing food particles (endocytosis). Furthermore, this flexibility also allows the membrane to rupture and reseal to expel undigested waste (exocytosis). Without this characteristic, Amoeba would be unable to perform ingestion or egestion.
