Zinc in its 2+ oxidation state is an essential metal ion for life. Zn2+ is found bound to many proteins that are involved in biological processes, but unfortunately Zn2+ is hard to detect by common chemical methods. Therefore, scientists who are interested in studying Zn2+-containing proteins frequently substitute Cd2+ for Zn2+, since Cd2+ 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 Cd2+ as a Zn2+ 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 Cd2+ to replace Zn2+ in enzymes is that Cd2+ substitution can decrease or even eliminate enzymatic activity. Can you suggest a different metal ion that might replace Zn2+ in enzymes instead of Cd2+? Justify your answer.
CEM 141 Lecture 23 – Nuclear Reactions and Bonding Dr. Jian Hu 26 October 2016 Energy changes in nuclear reactions Nuclear reactions have changes in mass (mass defect), but in chemical reactions, mass is conserved Mass-energy equivalence E=mc (Einstein) – E represents the “binding energy” that gets released when mass is converted to energy – m represents the mass in kg – c represents the speed of light (3x10 m/s) Mass defect: mass of the individual nucleons is greater than the mass of the product – mass defect is the difference the mass of the nucleons and the mass of the atom Mass defect = binding energy Practice: Each deuterium atom is formed by 1 proton, 1 neutron, and 1 electron. How much energy is released b