Which ion holds the ribosomal subunits together-

Options

A. `Ca^(+2)`
B. `Mn^(+2)`
C. `Mg^(+2)`
D. `Na^(+)`

Answer

**Step-by-Step Solution:**

1. **Understanding Ribosomal Subunits**: Ribosomes are composed of two subunits, the large and small subunits, which come together to form a functional ribosome. These subunits are held together by various interactions, including ionic interactions.

2. **Identifying the Ions**: The question provides four options: Calcium, Manganese, Magnesium, and Sodium. We need to determine which of these ions is most abundant and effective in holding ribosomal subunits together.

3. **Analyzing the Role of Magnesium**: Magnesium ions (Mg²⁺) are known to play a crucial role in stabilizing the structure of ribosomes. The high charge density of magnesium allows it to effectively neutralize the negative charges present on the RNA backbone of the ribosomal subunits.

4. **Comparing Other Ions**: While other ions like Sodium (Na⁺) and Potassium (K⁺) are present in biological systems, they do not have the same capacity to stabilize ribosomal subunits as magnesium does. In fact, at high concentrations, sodium and potassium can compete with magnesium and lead to the dissociation of ribosomal subunits.

5. **Conclusion**: Based on the analysis, the ion that holds the ribosomal subunits together is Magnesium (Mg²⁺). Its high charge density allows it to neutralize the negative charges of the RNA, facilitating the association of the ribosomal subunits.

**Final Answer**: Magnesium ion (Mg²⁺) holds the ribosomal subunits together.

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