Question

chapter 4: a tour of the ce. 9. describe the nuclear envelope and its function. 10. found within the nucleus are the chromosomes. they are made of chromatin. what are the two components of chromatin? when do the thin chromatin fibers condense to become distinct chromosomes? 11. what organelles are assembled in the nucelolus? 12. what is the function of ribosomes?

Explanation:

1. The nuclear envelope is a double - membrane structure that surrounds the nucleus. It separates the genetic material (DNA) from the cytoplasm and contains nuclear pores that regulate the exchange of substances like RNA and proteins between the nucleus and the cytoplasm.
2. Chromatin is composed of DNA and histone proteins. Thin chromatin fibers condense to become distinct chromosomes during cell division (mitosis or meiosis).
3. Ribosomal subunits are assembled in the nucleolus. The nucleolus combines ribosomal RNA (rRNA) with ribosomal proteins to form the small and large subunits of ribosomes.
4. Ribosomes are the sites of protein synthesis. They translate the genetic information carried by messenger RNA (mRNA) into polypeptide chains by linking amino acids together.

Answer:

1. Double - membrane surrounding nucleus, separates DNA from cytoplasm, has nuclear pores for substance exchange.
2. Components: DNA and histone proteins. Condense during cell division.
3. Ribosomal subunits.
4. Sites of protein synthesis.