Question

Describe the structure of the following with the help of labelled diagrams.

(i) Nucleus (ii) Centrosome

Answer 1

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Refer to the attachment..

Answer 2

Nucleus is a complex protoplasmic body connected by double membrane that includes all the genetic information necessary to regulate cellular metabolism and transmission it to posterity.

An organelle which serves as the animal cell's main organizing microtubule  core is known as centrosome.

Step by step explanation:

Nucleus:

Nucleus is a relatively large organel which controls all of the eukaryotic cell activities. Nucleus is a complex protoplasmic body connected by double membrane that includes all the genetic information necessary to regulate cellular metabolism and transmission it to posterity.

A nucleus is called interphase nucleus in the non-dividing phase, and a standard interphase nucleus is divided into nuclear envelope nucleoplasm or nuclear matrix, nucleolus, and chromatin.

• Nuclear envelope - It bounds outward the nucleus and separates it from the cytoplasm. It is composed of two outer and inner membranes. The inner membrane is smooth whereas the outer membrane may be smooth or ribosomes such as the RER may bear on its cytoplasmic surface. The outer membrane frequently connects to ER.
• Nucleoplasm - It is a transparent, colloidal and semi-fluid substance which fills the nucleus. It contains nucleolus, chromatin and  highly extended and elaborate nucleoprotein fibres.
• Nucleolus - It is a circular structure found in the nucleoplasm. It is not separated from the rest of the nucleoplasm, because a membrane does not bind anything. It is the location for the synthesis of ribosomal RNA.
• Chromatin - The nucleus of interphase comprises a free, distributed, and diffused nucleoprotein fibre network called chromatin. Chromatine fibers condense in order to form chromosomes.

Centrosome:

An organelle which serves as the animal cell's main organizing microtubule  core is known as centrosome. It is also present in some lower plant cells which participate in the formation of cilia or flagella spindles of basal bodies.

Centrosomes are composed of two centrioles arranged orthogonally, surrounded by an amorphous protein mass called pericentriolar material. Within the heart, is a centrosome. It has a cytoplasmic non-granular region called the centrosphere and two cylindrical structures called the centrioles. The two centrioles lie to one another at right angles.

Each centriole contains a whorl of nine triplet fibrils of fused microtubules running parallel to each other but at a 40 degree angle.

The centriole core has a protein rod named node. Node is linked to peripheral triplets by protein-bearing threads known as spokes.