Centrosome Structure and Centrioles — NEET Biology
📚 Practice ConceptCentrosome is an organelle usually containing two cylindrical structures called centrioles. They are surrounded by amorphous pericentriolar materials. Both the centrioles in a centrosome lie perpendicular to each other in which each has an organisation like the cartwheel. They are
Which of the following statements about the structure of centrioles in a centrosome is NOT correct? S1: A centrosome typically contains two cylindrical centrioles surrounded by amorphous pericentriolar materials. S2: The two centrioles in a centrosome are oriented parallel to each other. S3: Each centriole exhibits a cartwheel-like organisation with nine evenly spaced peripheral fibrils. S4: Each peripheral fibril in a centriole is composed of a doublet of tubulin protein. S5: The central proteinaceous hub of a centriole is connected to the peripheral fibrils by radial spokes.
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Correct answer: A — Only S2 and S4 are not correct
The core concept here is the detailed structural arrangement of centrioles within a centrosome. S1: A centrosome usually contains two cylindrical structures called centrioles, surrounded by amorphous pericentriolar materials. This statement is correct. S2: The two centrioles in a centrosome lie perpendicular to each other, not parallel. This statement is NOT correct. S3: Each centriole has an organisation like the cartwheel, made up of nine evenly spaced peripheral fibrils. This statement is correct. S4: Each of the peripheral fibrils in a centriole is a triplet of tubulin protein, not a doublet. The 9+2 array of cilia and flagella has doublets, but centrioles have triplets. This statement is NOT correct. S5: The central part of the proximal region of the centriole is proteinaceous and called the hub, which is connected with tubules of the peripheral triplets by radial spokes made of protein. This statement is correct. Therefore, statements S2 and S4 are NOT correct. The correct option is A because it accurately identifies the two statements (S2 and S4) that are incorrect based on NCERT. Options B, C, and D incorrectly identify the number or combination of incorrect statements.
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