Which of the following cell organelles is made up of ribosomal RNA and protein?
Ribosome
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.
| Organelle | Primary Composition | Made of rRNA and Protein? |
|---|---|---|
| Ribosome | Ribosomal RNA (rRNA), Proteins | Yes |
| Nucleus | Nuclear envelope (membrane), DNA, Proteins (Histones, enzymes), Nucleoplasm, Nucleolus | No (contains components, but not primarily the structure) |
| Golgi body | Membranes (Lipids, Proteins), Enzymes | No |
| Lysosome | Membrane, Hydrolytic Enzymes (Proteins) | No |
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
| Organelle | Composition | Key Function |
|---|---|---|
| Ribosome | rRNA and Proteins | Protein Synthesis (Translation) |
| Nucleus | Membrane, DNA, Proteins | Contains genetic material, controls cell activities |
| Golgi body | Membranes (cisternae) | Modify, sort, package proteins and lipids |
| Lysosome | Membrane, Digestive Enzymes | Break down waste and debris |
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.
Important Questions from Cell
In a plant cell, which one of the following contains their own DNA?
Which one of the following structures or components is not always present in living cells?
Which one of the following statements about animal cells and plant cells is correct?
- Which one of the following statements about vacuoles' is not correct?
- A cell is unable to synthesize lipids. Which of its cell organelles might be defective?
