Final answer:
Soluble iron and manganese can be sequestered by using siderophores, proteins like transferrin, and adjustments in pH to increase their solubility for uptake and transport in organisms. Ferritin can store iron in a concentrated form, and its release is aided by reductants like ascorbic acid.
Step-by-step explanation:
Soluble iron and manganese can be sequestered by utilizing specific organic ligands or molecules within biological systems. Organisms must mobilize, transport, and transfer essential transition metals such as iron from the environment to their internal systems. In the case of iron, to overcome the insolubility of Fe(OH)3, siderophores, which have a high affinity for Fe(III), are secreted to increase soluble iron concentrations.
Once inside the body, the transferrin protein complexes with Fe(III), aiding transport to where it is needed, either for immediate use or storage. Iron can be stored as ferritin, a large protein that oxidizes Fe2+ to Fe3+ and stores it in a concentrated form. When iron is required by a cell, ascorbic acid can reduce Fe3+ to the more soluble Fe2+, facilitating its release from ferritin.
Multicellular organisms may also adjust the pH of their gastrointestinal tract to dissolve Fe(III) salts, which are then absorbed and transported. Proteins that bind to Fe(III) fiercely also act as antibacterial agents by sequestering iron and preventing bacterial growth in nutrient-rich environments.