Question

Siderophores are small polydentate ligands and have a high affinity for:

• A. Fe
• B. Fe (II)
• C. Fe (III)
• D. Free Fe

Hint:

Remember the biological context of iron: in an oxygen-rich environment, iron is stable as insoluble Fe(III). Life needs a way to capture this form. Siderophores are the microbial solution, acting as high-affinity chelators specifically for Fe(III).

Answer 1

The Correct Option is C

Step 1: Core Idea:
Siderophores are small organic molecules made by microbes and plants to grab, dissolve, and move iron. The question focuses on the specific form of iron they're attracted to.
Step 2: Breakdown:
In air and at a neutral acidity, iron is mostly in the ferric state, Fe(III) or Fe\(^{3+}\). This form is hard to dissolve, usually forming ferric hydroxide [Fe(OH)\(_3\)], making it unusable. Siderophores solve this. They are ligands that strongly bind to Fe(III) ions, often using catecholate or hydroxamate groups. This creates a soluble complex that cells can import via specific receptors. While they can bind other metals, their attraction to Fe(III) is strongest. Fe(II) is the ferrous state, which is more soluble but less present in air.
Step 3: The Answer:
Siderophores strongly prefer the ferric iron ion, Fe (III).