Cell Structure Part IV: The Nucleus

<p>Euchromatin (C)</p> Signup and view all the answers

<p>They allow for controlled exchange of materials between the nucleus and cytoplasm. (A)</p> Signup and view all the answers

<p>It plays a crucial role in ribosome production. (C)</p> Signup and view all the answers

<p>Nucleoprotein, which is DNA conjugated with histone protein. (A)</p> Signup and view all the answers

<p>It serves as a suspension medium for the nuclear components. (A)</p> Signup and view all the answers

<p>An irregular spongy mass (A)</p> Signup and view all the answers

<p>13, 14, 15, 21, 22 (D)</p> Signup and view all the answers

<p>Directing protein synthesis (D)</p> Signup and view all the answers

<p>Mitochondrial DNA (C)</p> Signup and view all the answers

<p>G1, S, G2 (C)</p> Signup and view all the answers

<p>A pair of S-chromosomes (D)</p> Signup and view all the answers

<p>To facilitate the movement of RNA (C)</p> Signup and view all the answers

<p>Interphase consists of three stages. (A)</p> Signup and view all the answers

The nucleus is the control center of the cell, directing all metabolic activities and playing a vital role in heredity and cell division.

The nuclear envelope is a double membrane that encloses the nucleus, separating it from the cytoplasm. It is composed of an outer and inner membrane and is punctured by nuclear pores.

Chromatin is the complex of DNA and proteins that makes up chromosomes. It appears as basophilic granules under a light microscope.

Heterochromatin is a condensed, inactive form of chromatin. Its genes are mostly inactive.

Euchromatin is a relaxed, active form of chromatin. Its genes are usually active.

The nucleolus is a dense, spherical structure inside the nucleus where ribosomal RNA is produced. It appears as a basophilic region under a light microscope.

The nuclear sap is the fluid inside the nucleus that contains dissolved enzymes, nucleotides, and other molecules.

Interphase is the period of the cell cycle when the cell is not dividing. It consists of three phases: G1, S, and G2.

Ribosomal RNA (rRNA) is synthesized around "nucleolar organizer genes", which are located on specific chromosomes. These genes contain the DNA sequence for rRNA.

The nucleolus appears as a dark, basophilic mass under a light microscope. This is because it contains a high concentration of RNA, which stains intensely with basic dyes.

The nucleolus is not enclosed by a membrane and has a spongy, irregular structure. It's also surrounded by heterochromatin, which is condensed chromatin.

The nucleolus is involved in the synthesis and processing of rRNA, which is then combined with proteins to form ribosomal subunits. These subunits leave the nucleus and move to the cytoplasm, where they assemble into mature ribosomes.

Nuclear sap is a clear, semiliquid solution that fills the nucleus. It's also known as nucleoplasm.

Nuclear sap contains important molecules including proteins, enzymes, and nucleotides. These molecules are essential for DNA and RNA synthesis.

Nuclear sap acts as a medium for molecules like rRNA, mRNA, and tRNA to move around the nucleus. This movement is crucial for gene expression and protein synthesis.