Signaling between cells usually results in the activation of protein

Options

A. Kinases
B. Proteases
C. Lipases
D. Nucleases.

Answer

**Step-by-Step Solution:**

1. **Understanding Cell Signaling**: Cell signaling is the process through which cells communicate with each other using signaling molecules (ligands). These molecules bind to specific receptors on the target cells.

2. **Role of Ligands and Receptors**: When a ligand binds to its receptor, it forms a ligand-receptor complex. This complex is crucial for initiating a cellular response.

3. **Activation of Proteins**: The binding of the ligand to the receptor typically leads to the activation of specific proteins within the cell. One of the key types of proteins that get activated in this process is protein kinases.

4. **Function of Protein Kinases**: Protein kinases are enzymes that transfer phosphate groups from high-energy molecules (like ATP) to specific substrates (target proteins). This process is known as phosphorylation.

5. **Effects of Phosphorylation**: The phosphorylation of target proteins can lead to various cellular changes, including alterations in enzyme activity, changes in gene expression, or modifications in cellular metabolism.

6. **Conclusion**: Given the options provided (kinase, protease, lipase, nucleus), the correct answer is "kinase," as signaling between cells typically results in the activation of protein kinases.

**Final Answer**: Kinase

---