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IBMS > Biomineralisation > Flashcards

Biomineralisation Flashcards

Biomineralisation

1
Q

Define biominerlaisation

A
  • refers to the the processes by which organism form minerals
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1
Q

what is biosphere

A

life on earth

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2
Q

what is lithosphere

A

solid part of earth

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3
Q

Describe the origin of biominerlisation

A
  • taking place since water appeared on the earth surfaces
  • 3.5 Gyr - first prokaryotes and then eukaryotes developed the ability to form biominerals
  • 540 Myr ago organism form different phyla evolved the ability to form many of 64 different biominerals known to date
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4
Q

what is biominerlasiation responsible for

A
  • hard, resistant products of life which are mainly responsible for the Earths fossil record
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5
Q

why does biominerlasiton take place?

A
  • provide evolutionary advantages for many organisms
  • played an important role in shaping the survival strategies of these organisms
  • mechanical support
  • digestive processes
  • Protection/camouflage
  • Defense mechanism
  • Attack strategies
  • optical advantage
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6
Q

State two basic processes of biominerlation and there other forms of mineraltion

A
  • biologically induces minerlasiiton
  • Biologically controlled mineralisation
    • extracellular
    • intercellular
    • intracellular
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7
Q

describe biologically induced mineralisation

A
  • cell is a causative agent only, without control over mineral type or habit
  • chemical processes influenced by metabolic activities indirectly form specific minerals
    (e.g bacteria such as Thiobacillus ferooxidans can induce the mineralisation of minerals such as iron sulphide on metal surfaces )
  • cell surfaces acts as causative agents for nucleation and subsequent mineral growth
  • hetrogenetiy is hallmark
  • compositions of. minerals vary - morphology, water content, trace, sediment, rock record
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8
Q

Describe biologically controlled mineralisation

A
  • Organism guide mineral formation through cellular activities controlling nucleation, growth,morphology and final location
  • Typically occurs in isolated environments
  • varies in control across species
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9
Q

describe biological controlled extracellular mineralisation

A
  • cells produce matrix outside the cell
  • this matrix is genetically programmed to facilitate mineral formation
    (C-HAp crystal formation by ameloblasts)
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10
Q

describe biological controlled intercellular mineralisation

A
  • Typically occurs in single celled organism
  • epithelial surfaces of cells directs mineral formation
  • mineralisation between cells fill intercellular spaces ( Calcite formation by alcerous algae)
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11
Q

describe biological controlled Intracellular mineralisation

A

occurs within cells often in specialised vesicles
- some intracellular biominerals remain within cell
- others released by exocytosis or membrane fusion and may undergo secondary assembly
(Silica polymerisation in diatoms)

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12
Q

Define biominerals

A

Minerals that are produced by the activity of living things
- different properties to their inorganically formed counterparts
- span vast size range
- some organisms can Crete biominerals in seconds
some take thousands of years

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13
Q

how many biominerals are known to date

A

64

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14
Q

which bxomineral is the most abundant

A

calcium carbonate

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15
Q

what percentage does iron make up of biominerals

A

40%

16
Q

what % does calcium make up of biomienrlas

A

50%
- preferred cation for majority of organisms
attributed to roles calcium plays in cellular metabolism

17
Q

what % does hydrated biomaterials make up

A

60%
- contain water or hydroxyl group
favoured over dehydrated as they educe energy barriers for crystal nucleation and growth form aq

18
Q

what % makes up crystal/amorphous biominerals

A

25%

19
Q

what % make sup phosphates

A

25%
- carbonated hydroxyapapite - most abundant produced phosphate minerals
present in bones and teeth
- small and unstable
more soluble than HAP

20
Q

what is the hardest most mienralised tissue in the body

A

enamel
96% MINERAL

21
Q

Describe the structure of enamel

A
  • 5 nanometres wide elongated prisms
  • cross sections of majority of prisms exhibit a keyhole pattern
  • prism houses thousands of needle- like enamel crystals
  • hexagonal cross sections
  • 60nm in width
    30nm in thickness
22
Q

Describe the conceptual model for protein mediated enamel biominerlaisation

A
  • Ameloblasts develop distal Tomes processes as they move away from the enamel dentine junction
  • TP contribute to deposition and shaping of enamel
  • Ameloblasts secretes matrix proteins (amelogenin and non amelogenin) as well as mineral forming ions eg. calcium and phosphate
  • Amelogenin self assemble into nanospheres stabilising amorphous calcium phosphate (ACP) particles
  • Nanospheres could contain non-amelogenesis (enamelin and amelobaslting)
  • MMP-20 cleaves amelogenin C terminus promoting self assembly into nanochains for orientated nucleation of calcium phosphate clusters
    -ACP clusters fuse into elongated ribbons and transform into crystalline c-HAP
  • formed mineral crystals mainly grow in length
    MMP-20 cleaves amelognein N terminus, promoting nano spheres disassembly
  • amelogenin and other matrix proteins are further degraded by the serine proteinase KLK-4 allowing further growth of c-HAP
    -ameloblasts transition between ruffle and smooth ended states to regulate ion transport, pH and remove organic debris
    =c-HAp crsytal grow in thickness and width aided by protein amelotin
23
Q

describe key methods in studying enamel biominerlasition

A
  • x ray mciroputed tomography
    Synchrotron x ray diffraction
  • SEM
24
Q

Describe how X-RAY microcomputed tomography is used to study enamel biominerlisation

A
  • as maturation progresses, the bxomineral concentration increases and becomes more uniform
  • Gets mineral conc
  • biominerlaistion starts near the cusp and the EDJ moving cervically and towards the surface as a function of maturation
25
Q

Describe how Synchrotron X ray diffraction is used to study dental enamel biomienrlaistion

A
  • pass x ray and study diffraction
    orientation persist form early maturation of enamel to new maturation
    -crystals orientated approximately perpendicular to EDJ regardless the developmental stage
  • initial preferred directions of crystals persist form early through to full maturation
26
Q

Describe how SEM Is used to study dental enamel biominerlaistion

A
  • In fully developed enamel the spasm boundaries were more difficult to distinguish compared to developing enamel
  • indicates that mienrlaistion of prisms cores precede that of prisms boundaries
  • in devleoped tooth, the mineralisation is homogenous
27
Q

what does MMP20 do

A

-cleaves amelogenin C terminus - promoting self assembly into nano chains for orientated nucleation of calcium phosphate clusters
- cleaves amelogensins N terminus- promoting nanpsphers disassembly

28
Q

what does nanosphers contain

A

ameolgenin and non amelogenin (enamel and ameloblastin)

29
Q

what does serine proteases KLK-4 do?

A
  • degrade amelogenin and other matrix proteins allowing further growth of c-HAp

IBMS (6 decks)

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