Oral Biochemistry Flashcards
Define ‘biomineralization’
process by which organisms form minerals
Define ‘amorphous biomineralization’
Mineral structure doesn’t have regular size, shape or spatial organization
Define ‘crystalline biomineralization’
Atoms in mineral are organized in repeated units
How can such complex shapes of minerals form within living organisms?
Scaffold - proteins (e.g. collagen) that give a rigid frame on which the mineral can form
Hydroxyapatite - filling material that fills the scaffold frame
Describe the two steps to crystallization
1) Nucleation: local region of solvent become saturated with solute, and solute molecule create a stable cluster. Requires molecules to line up just right for crystallization. Rare for complex crystals.
2) Growth: subsequent growth after nucleation has occurred.
T/F - Nucleation is the easy step in mineralization (i.e. takes the shortest)
False, takes the longest, and is the difficult step
Describe ‘dissolving’
Crystal components becoming integrate with water:
- Gravity wants precipitates to form
- Water surrounds the ion to oppose gravity
- Increase temperature allows water to be “burrowed” by multiple ions; thus, increasing solubility
Define solubility constant (Ksp)
Measure of how soluble a substance is
Define Ksp
This is the product of the dissolved ion concentrations in solution at equilibrium.
Higher Ksp = Higher solubility
Define saturated solution conditions
Ion product = Ksp
Define supersaturated conditions
- Ion product > Ksp
- Precipitation/mineralization favoured
Define undersaturated conditions
- Ion product < Ksp
- Dissolution/demineralization favoured
When does enamel begin to dissolve?
- When hydroxyapatite Ksp = 0.7 mM^2 (very low)
- HA Ksp increases exponentially with lowering pH
- Saliva become unsaturated when pH < 5
Define ‘Unit cells’
Regular repeated structure of crystals that fit together specifically. All atoms in a unit cell have a specific space and location (other atoms won’t fit there)
What is nucleation?
Nucleation is the formation of a critical amount of unit cells that act as template for new crystals to form.
Define matrix protein
Template protein to position the atoms to hydroxyapatite.
Name functions of matrix vesicles
- Concentrate the intracellular phosphate and calcium
- Secrete the matrix vesicle to the cell surface
- Provide high concentration of “supplies” to the crystal growth site
List bone composition’s organic and inorganic material
Organic material:
- Cell
- Collagen
- Glycosaminoglycans
- Proteoglycans and proteins
Inorganic material:
- Hydroxyapatite
- Calcium carbonate
Describe intramembranous ossification
Formed directly in loose mesenchyme from an osteoblast-secreting scaffold and matrix vesicles, then calcifying:
- bone that are constantly under tension
- Irregular bones (e.g. skull bones)
Describe ‘endochondral ossification’
Formed from the replacement of a hyaline cartilage model. Primary and secondary ossification centres form:
- Bones that are needed to perform immediately and are constantly under pressure
- Long bones
Describe osteoclast/osteoblast activity balance
Osteoblasts secrete RANKL and a decoy protein (OPG) that binds with the RANKL. If PTH is present, the decoy protein product is blocked. This allows the RANKL to bind with RANK receptors on pre-osteoclasts
- RANK receptors trigger production and maturation of osteoclasts
- PTH triggers osteoclast activity, by binding decoy protein (OPG)
- This ensures that osteoclastic activity only occurs in the presence of active osteoblasts
- This ensure that osteoblastic activity always matches osteoclastic activity.
Clinically, how do you get netloss of bone during inflammation (e.g. alveolar bone loss in root inflammation)?
- Inflammation and bacteria intermediates bind directly to the RANK receptor and activate the RANK cascade, but not through the osteoblasts: Trigger osteoclast activity, disproportionally to osteoblast activity.
- Since osteoblast/osteoclast activity is so linked, replacement of loss bone is slow and often permanent.
