Let's analyze each statement about the **α-carbon** (alpha carbon) in the context of amino acids, since that's the most common context for this term. ### 1. **The α-carbon is always bonded to four different chemical groups.** - **Explanation:** In standard amino acids (except glycine), the α-carbon is bonded to: - An amino group (-NH₂) - A carboxyl group (-COOH) - A hydrogen atom (-H) - A unique side chain (R group) - For **glycine**, the R group is another hydrogen, so the α-carbon is bonded to two hydrogens (i.e., not four different groups). - **Conclusion:** This statement is **NOT true**. The α-carbon is **not always** bonded to four different chemical groups; glycine is the exception. --- ### 2. **The α-carbon is always bonded to the amino group.** - **Explanation:** By definition, the α-carbon in amino acids is the central carbon atom attached directly to the amino group. - **Conclusion:** This statement is **true**. --- ### 3. **The α-carbon is always bonded to the carboxylic acid group.** - **Explanation:** Similarly, the α-carbon in amino acids is also always attached to the carboxyl group. - **Conclusion:** This statement is **true**. --- ### 4. **The α-carbon always has four chemical bonds.** - **Explanation:** The α-carbon is a carbon atom, and carbon atoms always form four covalent bonds due to their tetravalency. - **Conclusion:** This statement is **true**. --- ## **Final Conclusion** The statement that is **NOT true** is: > **The α-carbon is always bonded to four different chemical groups.** **Reason:** Glycine's α-carbon is bonded to two hydrogens, so not all four groups are different. The other statements are true for all amino acids.