Question

5. Read the following statements and choose the correct option. [NCERT Pg. 126, 129] 

Statement A : No organelles, like the ones in eukaryotes, are found in prokaryotic cells except for ribosomes. 

Statement B: Fimbriae are known to help in attaching the bacteria to rocks in streams and also to the host tissue. 

(1) Only statement A is correct,

 (2) Only statement A is incorrect,

 (3) Both statements are correct,

 (4) Both statements are incorrect

Answer 1

Correct option is (3) Both statements are correct

Ribosomes are specialized cell organelles composed of RNA and protein. They are present in both prokaryotic as well as eukaryotic cells. Every living cell requires it for the production of the proteins. Ribosomes are non membrane-bound organelle. They are essential cytoplasmic organelles present in close association with the endoplasmic reticulum. Ribosomes are present in the form of tiny particles in a large number of cells and are mainly composed of RNA and protein. They are named as the 70s (found in prokaryotes) or 80s (found in eukaryotes). The letter S refers to the density and the size, referred to as Svedberg’s Unit. Both 70s and 80s ribosomes are made up of two subunits. Ribosomes are either encompassed within the endoplasmic reticulum or are freely traced within the cell’s cytoplasm.

Fimbriae are fine bristle-like structures of bacteria, which help in attachment with substratum. Fimbriae are long filamentous polymeric protein structures located at the surface of bacterial cells. They enable the bacteria to bind to specific receptor structures and thereby to colonize specific surfaces. Like flagella, they are composed of protein. Fimbriae are shorter and stiffer than flagella, and slightly smaller in diameter. Generally, fimbriae have nothing to do with bacterial movement (there are exceptions, e.g. twitching movement on Pseudomonas).