Question at position 30 Iodide is oxidized to hypoiodite in the gastrointestinal tract, providing which of the following functions?OrganificationPathogen protectionIon transportMetabolic regulationSecond messenger单项选择题
A
Organification
B
Pathogen protection
C
Ion transport
D
Metabolic regulation
E
Second messenger

Question

Question at position 30 Iodide is oxidized to hypoiodite in the gastrointestinal tract, providing which of the following functions?OrganificationPathogen protectionIon transportMetabolic regulationSecond messenger单项选择题

A

Organification

B

Pathogen protection

C

Ion transport

D

Metabolic regulation

E

Second messenger

BlackTom AI · Accepted Answer

Iodide is oxidized to hypoiodite (HOI) by peroxidase enzymes in mucosal secretions, and HOI acts as an antimicrobial oxidant that inactivates bacteria, viruses and other pathogens.

1) Relevant knowledge points and concepts
- The lactoperoxidase (and related peroxidases) system in saliva, milk and gastrointestinal secretions uses hydrogen peroxide to oxidize small anions such as I– (iodide) and SCN– (thiocyanate).
- The chemical reaction (catalyzed by peroxidase): I– + H2O2 + H+ → HOI + H2O (formation of hypoiodous acid/hypoiodite).
- Hypoiodite/hypoiodous acid are reactive oxidants that iodinate and oxidize microbial cell components (proteins, lipids, enzymes), leading to microbial killing or growth inhibition.
- “Organification” is the enzymatic incorporation of iodide into tyrosyl residues of thyroglobulin in the thyroid gland (thyroid peroxidase), not a function of GI hypoiodite.

2) Step-by-step reasoning
- Iodide present in secretions is available to mucosal peroxidases.
- Peroxidase uses H2O2 to oxidize I– to HOI (shown in reaction above).
- HOI is chemically active and modifies microbial macromolecules, disrupting cell walls, enzymes and replication processes.
- This provides a first-line innate immune defense on mucosal surfaces—i.e., pathogen protection.

3) Intermediate/calculation steps (chemical)
- Substrate: I– (iodide)
- Oxidant: H2O2 (hydrogen peroxide)
- Enzyme: lactoperoxidase (LPX)
- Net: I– + H2O2 + H+ → HOI + H2O

4) Why the correct answer is correct
- The product HOI is an antimicrobial oxidant; its primary physiologic role in the GI tract and secretions is to protect against microbes. That aligns directly with “Pathogen protection.”

5) Why other options are incorrect
- Organification: specific to thyroid hormone synthesis (thyroid peroxidase in thyroid), not GI hypoiodite activity.
- Ion transport: refers to movement of ions (e.g., NIS transports iodide into thyroid), not an oxidative antimicrobial function.
- Metabolic regulation: HOI is not a general metabolic regulator.
- Second messenger: HOI does not serve as a cellular second messenger signaling molecule.

6) Conclusion
The correct function provided by oxidation of iodide to hypoiodite in the gastrointestinal tract is pathogen protection, which matches the provided answer: Pathogen protection.

Question at position 30 Iodide is oxidized to hypoiodite in the gastrointestinal tract, providing which of the following functions?OrganificationPathogen protectionIon transportMetabolic regulationSecond messenger单项选择题

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