Biomineralisation 1 Flashcards
what are the principles of nucleation and growth? and barriers to growth?
mineral dissolution involves breaking bonds.
mineral formation involves forming bonds.
barriers to nucleation:
- must overcome electrostatic repulsion forces
- needs enough energy to overcome activation barrier
- need to eliminate hydration shells around solutes - ions in water area surrounded by water molecules due to attraction of charges
- surrounding ligands must be removed
- a new interface can be formed: nucleation
What is the 1st step in nucleation
Formation of a nucleus of a new phase (the mineral) within the old phase (solution)
- solution must be supersaturated in ions of mineral being formed
- nucleation occurs by random collision of ions or on a surface
- surface acts as a catalyst, reduces surface tension, lower Ea and increases nucleation rate
What is the growth of initial phase of nucleation
ions adsorb starting at the nucleus. initial phase is usually amorphus, with no intrinsic structure
What is the Ostwald Step Rule
Process of precipitating highly soluble (least-stable) phase first, then precipitating progressively more stable phases
what is step 3: the growth of crystalline phase?
crystalline phases use the amorphous phase as a template.
alternatively, dehydration and internal rearrangement can also transform
what is the Ksp and Q (IAP)
Ksp = concentration of solution at equilibrium Q = ion activity product (IAP) concentration of ions in solution as measured
What is biologically induced mineralisation
minerals which form as a by-product of metabolic activity or other interactions between cells and their environment.
Occurs externally. nucleation on cell surfaces. enzymatically mediated changes in redox state
What is biological controlled mineralisation?
the microorganism controls all stages of mineralisation in order to serve a physiological purpose. requires energy. occurs in cyptoplasm or cell wall.
specific ions are actively introduced and their concentrations to control
