Zincin its \(2+\) oxidation state is an essential metal ion for life. \(\mathrm{Zn}^{2+}\) is found bound to many proteins that are involved in biological processes, but unfortunately \(\mathrm{Zn}^{2+}\) is hard to detect by common chemical methods. Therefore, scientists who are interested in studying \(\mathrm{Zn}^{2+}\) -containing proteins frequently substitute \(\mathrm{Cd}^{2+}\) for \(\mathrm{Zn}^{2+},\) since \(\mathrm{Cd}^{2+}\) is easier to detect. (a) On the basis of the properties of the elements and ions discussed in this chapter and their positions in the periodic table, describe the pros and cons of using \(\mathrm{Cd}^{2+}\) as a \(\mathrm{Zn}^{2+}\) substitute. (b) Proteins that speed up (catalyze) chemical reactions are called enzymes. Many enzymes are required for proper metabolic reactions in the body. One problem with using \(\mathrm{Cd}^{2+}\) to replace \(\mathrm{Zn}^{2+}\) in enzymes is that \(\mathrm{Cd}^{2+}\) substitution can decrease or even eliminate enzymatic activity. Can you suggest a different metal ion that might replace \(Z n^{2+}\) in enzymes instead of \(C d^{2+} ?\) Justify your answer.

Step by step solution

01

(Part a: Properties and Positions of Zn²⁺ and Cd²⁺ in the Periodic Table)

Both Zn²⁺ (zinc) and Cd²⁺ (cadmium) are members of the d-block elements in Group 12 of the periodic table. They share similar chemical properties, such as similar ion size and the same charge, due to their position and electronic configuration. These similarities make Cd²⁺ a possible substitute for Zn²⁺ in proteins and enzymes.

02

(Part a: Pros of Using Cd²⁺ as a Zn²⁺ Substitute)

One of the main advantages of using Cd²⁺ as a Zn²⁺ substitute is that it is easier to detect through common chemical methods due to its spectroscopic properties. This makes it easier for scientists to study the role of metal ions in biological systems where Zn²⁺ is involved.

03

(Part a: Cons of Using Cd²⁺ as a Zn²⁺ Substitute)

There are some disadvantages to using Cd²⁺ as a substitute for Zn²⁺ as well. Cd²⁺ is toxic and can cause harm to the organisms being studied if used in large amounts. Additionally, it may interfere with the normal function of the proteins and enzymes it is bound to, causing decreased or eliminated enzymatic activity, which can lead to errors in experimental results.

04

(Part b: Alternative Metal Ion and Justification)

A possible alternative metal ion that might replace Zn²⁺ in enzymes is Mg²⁺ (magnesium). Mg²⁺ has a similar charge (+2) and size to Zn²⁺, making it a potential candidate for substitution. Additionally, magnesium is an essential element for life, is involved in many biological processes, and is less toxic than cadmium. However, it should be noted that the substitution of Mg²⁺ may still alter the structure and function of the enzymes, so it is important to consider the specific context and experimental conditions when suggesting alternative metal ions.

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