Understanding Cell Organelle Composition

The question asks us to identify a specific cell organelle based on its fundamental building blocks: ribosomal RNA (rRNA) and protein. Different organelles within a cell have unique compositions and functions that allow them to carry out specialized tasks necessary for cell survival.

Analyzing the Composition of Cell Organelles

Let's examine the given options and their known compositions:

• Ribosome: Ribosomes are crucial cellular machinery responsible for protein synthesis. They are composed of two subunits, both of which are made up of ribosomal RNA (rRNA) molecules and a large number of proteins. This combination of rRNA and protein forms the functional structure of the ribosome.
• Nucleus: The nucleus is a large, membrane-bound organelle that contains the cell's genetic material (DNA) organized into chromosomes. Its composition includes the nuclear envelope (a double membrane), nucleoplasm, chromosomes (DNA and proteins like histones), and the nucleolus (where rRNA is transcribed and ribosomes are assembled). While it contains components involved in ribosome synthesis, the nucleus itself is not primarily made of just rRNA and protein in the sense the question implies for a specific organelle unit.
• Golgi body (Golgi apparatus): The Golgi body is an organelle consisting of a stack of flattened membrane-bound sacs called cisternae. It modifies, sorts, and packages proteins and lipids for secretion or delivery to other organelles. Its primary composition is membrane lipids and associated proteins involved in transport and modification. It does not fit the description of being made purely of rRNA and protein.
• Lysosome: Lysosomes are spherical, membrane-bound organelles containing digestive enzymes. They are involved in breaking down waste materials, cellular debris, and pathogens. Their composition includes a single membrane surrounding an acidic lumen containing various hydrolytic enzymes (which are proteins). They are membrane-bound sacs of enzymes, not structures made of rRNA and protein.

Identifying the Correct Organelle

Based on the detailed composition of each organelle, the ribosome is the only one that is fundamentally constructed from ribosomal RNA (rRNA) and proteins. These two components come together to form the ribosomal subunits, which then combine to form a functional ribosome for translation (protein synthesis).

Therefore, the cell organelle made up of ribosomal RNA and protein is the ribosome.

Conclusion

The organelle specifically known to be composed of ribosomal RNA and protein is the ribosome. Its unique composition directly relates to its function in synthesizing proteins based on genetic instructions.

Revision Table: Cell Organelles

Additional Information: Ribosomal RNA (rRNA)

Ribosomal RNA (rRNA) is a type of non-coding RNA that is a primary component of ribosomes, essential cellular machines that catalyze protein synthesis. In eukaryotes, there are typically four types of rRNA molecules (18S, 5.8S, 28S, and 5S), while prokaryotes have three (16S, 23S, and 5S). These rRNA molecules fold into complex 3D structures and, along with ribosomal proteins, assemble to form the large and small ribosomal subunits. The rRNA plays a crucial role in recognizing the mRNA codon, binding tRNA, and catalyzing the formation of peptide bonds between amino acids during translation.