Amoeba Proteus Structure and Function

In this amoeba proteus structure and function post we have briefly explained about amoeba proteus anatomy, internal organs, functions, and life cycle of amoeba organism.

Amoeba proteus is a single-celled organism found in ponds, lakes, freshwater pools, and slow-moving streams. It is a unicellular organism and measures about 250 to 600 µm in maximum diameter and so transparent that is invisible to naked eyes. 

It usually, feeding on algae, bacteria, and other microorganisms. It looks as an uneven, jelly-like small mass of hyaline protoplasm under the microscope. The outline of an amoeba’s body changes throughout time due to the production of microscopic finger-like outgrowths called pseudopodia. 

Pseudopodia are transitory finger-like extensions with blunt rounded tips that the body constantly gives out or retracts. Pseudopodia are generated in large numbers at the same time. The pseudopodia of the amoeba organism allow it to move around. It also aids in the capture of food. The body of an amoeba organism has three main sections, similar to that of a normal cell: plasma lemma or plasma membrane, cytoplasm, and nucleus.

structure of Amoeba

Structure of Amoeba Organism

Amoeba Proteus Structure and Function

Plasma Membrane

The plasma lemma of an amoeba organism is a very thin, fragile, and elastic cell membrane. It is made up of a two-layer structure comprising lipid and protein molecules. This selectively permeable membrane controls the exchange of water, oxygen, and carbon dioxide between the animal and the environment. Small ridge-like projections emerge from the plasma lemma’s outer surface, which aid in the organism’s attachment to the substratum.


Ectoplasm and endoplasm are the two types of cytoplasm (Structure of Amoeba Proteus). Just beneath the plasma lemma, the ectoplasm forms the outer, rather firm layer. It’s a hyaline layer that’s thin, clear, and non-granular. It thickens into a hyaline cap at the terminals of pseudopodia as it advances.

Ectoplasm: There are several prominent longitudinal ridges in the ectoplasm. The ectoplasm is classified as a supporting layer because it contains longitudinal ridges. The ectoplasm fully surrounds the endoplasm, which constitutes the primary body mass. It’s a fluid that’s granular and diverse. An exterior, relatively rigid plasmagel and a more fluid inner plasmasol make up the endoplasm.

Endoplasm: The plasmagel is more solid and granular, but its granules do not move. Endoplasm comprises a number of essential inclusions, including the nucleus, contractile vacuole, food vacuoles, mitochondria, Golgi apparatus, fat globules, and plate-like or bipyramidal crystals, in addition to granules. A number of organelles or structures are suspended in endoplasm. The nucleus, contractile vacuole, food vacuoles, and water globules are the organelles in question.


There is a single prominent nucleus in amoeba proteus. In juvenile specimens, the nucleus appears as a biconcave disc, although it is frequently folded and convoluted in older specimens. A solid nuclear membrane or nuclear envelope surrounds the nucleus, which contains a transparent achromatic substance with minute chromatin granules or chromidia evenly dispersed near the surface. 

The nucleoplasm is in short supply. Massive or granular nucleus is the name given to such a nucleus. A nucleus in an amoeba serves as a storage centre for the cell’s genetic material as well as a coordination centre for the cell’s activities.

Contractile vacuole

A transparent, spherical, and pulsing vacuole filled with a watery fluid can be found near the posterior end of the endoplasm. A unit membrane surrounds this vacuole, which is known as the contractile vacuole. The contractile vacuole (CV) complex is an osmoregulatory organelle of free-living amoeba organism and protozoa, which controls the intracellular water balance by accumulating and expelling excess water out of the cell, allowing cells to survive under hypotonic stress as in pond water.

Food vacuoles

In the endoplasm, there are several feeding vacuoles. These are non-contractile and come in a variety of sizes. The food vacuoles are moved about by the endoplasmic reticulum. Food digestion takes occur within the food vacuole.  Food vacuole is a membrane-enclosed sac, which has a digestive function. It is present in amoeba organism. They work as an intracellular stomach, digesting the ingested food. It contains digestive enzymes, which break down the food and then it is released into the cytoplasm for utilization.

Water globules

The water vacuole is the smallest transparent, circular water filled vacuole in the amoeba organism body. It can be one or more in number. The water vacuole does not contract. The water vacuole stores water and maintains the body’s water equilibrium. Water globules, It contains water and keeps the balance of the water constant of the body.

Other Organelles

Golgi bodies: Small tubules and vesicles resemble Golgi bodies. Food secretion and excretion are aided by this substance. Mitochondria: Mitochondria are found around contractile vacuoles and are oval in shape with tubular cristae. They play a role in respiration as well as energy production. Crystals: Plate-like or bipyramidal crystals have been discovered. The faecal chemicals released during metabolism are thought to be the source of these crystals.

Life cycle

Amoeba organism reproduction is a cyclical process that occurs at regular periods. Amoebae reproduce mostly by asexual means, such as binary fission, multiple fission, and sporulation.

Binary fission

Binary fission is a type of nuclear fusion. It’s the most common way of reproduction. Mitosis is a process in which the entire body divides into two daughter amoebae. Nuclear division (karyokinesis) occurs first, followed by cytoplasmic division (cytokinesis). This occurs when the weather is favourable.

structure of Amoeba

Binary Fission of Amoeba Organism


Amoeba organism reproduces internally by forming spores in unfavourable environments. It begins with the nuclear membrane breaking down and the release of chromatin blocks into the cytoplasm. Each chromatin block develops a nuclear membrane and is transformed into a miniature daughter nucleus. 

Amoebulae are created when newly formed nuclei are surrounded by cytoplasm. The spore-membrane or spore case is formed by the peripheral cytoplasmic layer of amoebulae. A single parent amoeba organism produces about 200 such spores. Finally, the parent amoeba’s body disintegrates, releasing the spores. The spores are dormant for a while before forming a juvenile amoeba when they are exposed to favourable conditions.

structure of Amoeba

Sporulation of Amoeba

Multiple fission

Amoeba organism divides through multiple fission in unfavourable conditions. It loses its pseudopodia, condenses into a sphere, and secretes a three-layered cyst around itself. Its nucleus divides several times during mitosis, resulting in 500-600 daughter nuclei. Each daughter nuclei becomes engulfed in cytoplasm and splits into tiny amoebulae. When the cyst is exposed to favourable conditions, it ruptures, releasing the amoebulae, which quickly mature into adult amoeba organism.

Multiple Fission of Amoeba Organism, Stages of Multiple Fission of Amoeba Organism


Amoeba organism has a remarkable ability to regenerate. Each piece regenerates into a new amoeba when cut into little pieces. However, regeneration occurs solely from the nucleus-containing segment of the cell. Amputated pieces without a nucleus are doomed to perish.

Further Readings