Name: Protozoans
Uploaded: 2019-07-19
Duration: 4 min 57 s
Description: Beware when you are in a moist environment, such as near ponds and lakes. There might be organisms like Protozoans around you that you cannot see without a microscope.

Question

Describe the cell structure of a typical protist.

Accepted Answer

Protists are the unicellular, eukaryotic organisms that contain all the cell organelles along with the nucleus. The typical protist cell can be described as follows:

The organisation is of two-envelope type with an outer cell membrane around the cytoplasm and a number of membrane-bound organelles inside the cytoplasm.

These cells may be naked or covered by a cell wall, pellicle, shell or cuticle.

A well-defined nucleus is present. These can be uninucleate, binucleate or multinucleated. The genetic material is linear DNA, enclosed by a nuclear envelope, complexed with proteins and organised into distinct chromosomes.

The cytoplasm contains besides ribosomes, a variety of organelles such as mitochondria, plastids (in photosynthetic protists) lysosomes, cytoskeleton, endoplasmic reticulum and Golgi bodies. Ribosomes are of two types, 80 S and 70 S ribosomes. Many have centrioles also.

The cytoplasm is always in motion and the phenomenon is called cytoplasmic streaming or cyclosis.

Cell wall, if present, contains cellulose or chitin. Locomotion can occur through flagella, cilia, pseudopodia, contractions and mucilage extrusion. Flagella and cilia, when present, have 9 + 2 patterns of microtubular strands.

A cell of Euglena (a Protist) that show a connecting link between both animals and plants has been shown below:

Describe the cell structure of a typical protist.

Important Questions on Kingdom–Protista

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