lecture 17: biomineralization

Question 1

Biomineralization

Answer 1

• Refers to processes by which organisms form solids from inorganic precursors (anions & cations)
• Organisms cannot violate physical laws of thermodynamics
• Organisms can control location, growth rate, shape, and type of biomineral deposited

Question 2

where are biominerals found

Answer 2

EVERYWHERE

Question 3

Mineral Component

Answer 3

• Solid consisting of inorganic anion + cation
• Minerals are defined by their chemical
  composition AND morphology
• Amorphous or crystalline

e.g. calcium carbonate (CaCO3) can occur as: Different crystal morphologies
* Vaterite,
* Calcite
* Aragonite
* Amorphous

***components are same - CaCO3, but arranged in different way

Question 4

Types of Biominerals

Answer 4

• ~ 60 different types of biominerals
• Common cations:
  – Calcium, Silica, Iron, Manganese, Zinc, Copper
• Common anions:
  – Carbonate, Phosphate, Sulfate

Question 5

Why so much calcium?

Answer 5

over 50% is calcium

bc of Phosphate

also calcium phosphate
- our bones
- brachiopod shells are this too
– calcium is abundant in marine systems
— calcium ions can precipitate phosphate
- almost everything requires phosphate ions to function
— cellular respiration - know how to pump calcium already

Question 6

Functions of Biominerals

Answer 6

1. Stiffen skeletal levers
2. Protection – armour
3. Harden jaws
4. Anchorage - like tubeworms and corals - not just armour, but anchors them to substrate
5. Storage system for metabolically important ions
6. Sensory reception
   - Gravity
   - Earth’s magnetic field
   *** examples: statocysts in cnidarians, magnetite crystals in bacteria

Question 7

Mechanism of Biomineralization

Answer 7

1) Space delineation

2) Subdivision of space by organic matrix

3) Generating saturated solution

4) Nucleation

5) Growth and shape modulation

6) Cessation

Question 8

Space Delineation
for Mineral Nucleation & Growth

Answer 8

control where biomineralization happens -

**has to happen in controlled space or volume

Question 10

Generating saturated solution of ions

Answer 10

need calcium and carbonate

• pump w CO2
• spend energy to pump ions into here
• the CO2 in water will form carbonate ions (CO3) and calcium —> calcium carbonate

Question 11

Mollusc shells often have multiple shell layers

Answer 11

• Layers may consist of calcite or aragonite
• Different layers may have different crystal orientations

Question 12

Arresting crack propagation

Answer 12

requires more energy to break bc diff material

need more energy to keep
cracking thru diff materials

take more energy to make a big fracture from a microfracture if different material

ex//
- Mollusc shell: plywood construction
– Strengthens by resisting crack propagation

Question 13

how to resist crack propagation?

Answer 13

1) Strengthens by resisting crack propagation - having different materials

2) gap adds a need for energy - having gaps and voids make cracks stop at this spot

crack cant go around has to go through

an EXAMPLE is porous echinoderm ossicles

Question 14

why is Shell Dissolution important

Answer 14

1) Enlarge shell apertures for water flow e.g. scaphopods, keyhole limpets

2) Enlarge living space

• cone snails get around the thin cracking
  from predators by having a non-existent spire
• but this means they have to dissolve their own
  shell over and over

Question 15

reasons for shell dissolution w examples (5)

Answer 15

1. Enlarge shell apertures for water flow
   e.g. scaphopods, keyhole limpets
2. Enlarge living space
   e.g. cone snails
3. Buffering of physiological acids
   e.g. during anaerobic metabolism
4. Remodeling during morphogenesis
   e.g. nudibranch larval shell
5. Mineral recycling
   e.g. crustacean molting cycle

Question 16

ocean acidification

Answer 16

Decreased ocean pH and carbonate ions due to burning of fossil fuels

Major detrimental affect of high atmospheric CO2 on calcifying organisms is depression
of carbonate ion concentration