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#zinc

5 public questions tagged with this topic.

Fertilization in mammals-iv

Polyspermy block by zinc involves:

Zinc spark released upon fertilization delivers concentrated zinc into perivitelline space and zona matrix. Zinc binding causes physicochemical alterations of ZP glycoproteins, facilitating ovastacin-mediated cleavage of ZP2 and enhancing disulfide crosslinking, reducing zona solubility and sperm binding sites. This zona hardening provides sustained block to polyspermy complementing fast electrical block. Zinc does not lyse sperm nor alter egg membrane potential directly, and does not regulate capacitation. Experimental chelation of zinc preserves zona softness allowing supernumerary sperm binding, while exogenous zinc induces hardening even without fertilization, demonstrating zinc as key regulator of zona-based polyspermy defense.

Ref: Duncan FE et al., PNAS 2016: Zinc-induced zona pellucida hardening as physicochemical block to polyspermy in mice.

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Enzyme Kinetics

Which of the following cofactors is required by carbonic anhydrase?

Zinc (Zn²⁺) is the scientifically accurate answer to this question. Within the study of Enzymes Basics, this concept is well-established through extensive research and is documented in standard scientific literature. The specific properties, mechanisms, or characteristics of Zinc (Zn²⁺) directly address what is being asked. Among the other options, Iron (Fe²⁺), Copper (Cu²⁺), and Magnesium (Mg²⁺) do not correctly answer this question because they either refer to different concepts, describe properties of other molecules or processes, or represent common misconceptions about this topic.

Ref: Lehninger Principles of Biochemistry, Nelson & Cox, 8th Ed., Ch. 6

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