Introduction Bone is made up of organic component 40% of dry weight inorganic component 60% of dry weight Organic component Components include collagen 90% of organic component primarily type I collagen provides tensile strength it is a triple helix composed of one alpha-2 and two alpha-1 chains proteoglycans responsible for compressive strength inhibit mineralization composed of glycosaminoglycan-protein complexes matrix proteins includes noncollagenous proteins function to promote mineralization and bone formation three main types of proteins involved in bone matrix osteocalcin most abundant non-collagenous protein in the matrix (10%-20% of total) produced by mature osteoblasts function promotes mineralization and formation of bone directly involved in regulation of bone density attracts osteoclasts signaling stimulated by 1,25 dihydroxyvitamin D3 inhibited by PTH clinical application marker of bone turnover can be measured in urine or serum osteonectin secreted by platelets and osteoblasts function believed to have a role in regulating calcium or organizing mineral in matrix osteopontin function cell-binding protein cytokine and growth factors small amounts present in matrix aid in bone cell differentiation, activation, growth, and turnover include IL-1, IL-6, IGF, TGF-beta, BMPs Inorganic component Components include calcium hydroxyapatite (Ca10(PO4)6(OH)2 provides compressive strength osteocalcium phosphate (brushite)
QUESTIONS 1 of 4 1 2 3 4 Previous Next (OBQ13.119) Which of the following components of bone is most responsible for compressive strength? Review Topic QID: 4754 1 Type I collagen 38% (1573/4176) 2 Osteocalcin 20% (852/4176) 3 Proteoglycans 38% (1566/4176) 4 Osteonectin 2% (101/4176) 5 Osteopontin 1% (62/4176) ML 5 Select Answer to see Preferred Response PREFERRED RESPONSE 3 (OBQ08.13) All of the following are true regarding osteocalcin EXCEPT which of the following? Review Topic QID: 399 1 It is the most prevalent non-collagenous protein in bone 17% (331/1921) 2 It is expressed by mature osteoblasts 11% (208/1921) 3 It is considered a marker for osteoblast differentiation 12% (237/1921) 4 It is a glycoprotein that binds calcium 39% (756/1921) 5 Higher levels are correlated with increases in bone mineral density during osteoporosis treatment 19% (373/1921) ML 4 Select Answer to see Preferred Response PREFERRED RESPONSE 4 (OBQ05.138) All of the following statements are true of osteocalcin EXCEPT: Review Topic QID: 1024 1 It is the most abundant noncollagenous protein of bone 7% (105/1463) 2 It is secreted by osteoclasts 70% (1019/1463) 3 It is involved in mediating calcium homeostasis 8% (122/1463) 4 It has been used as a biochemical marker of bone formation 7% (98/1463) 5 It is part of the organic matrix of bone 7% (109/1463) ML 2 Select Answer to see Preferred Response PREFERRED RESPONSE 2 (OBQ05.70) Ca10(P04)6(OH)2 is the chemical formula of Review Topic QID: 956 1 Calcium hydroxyapatite 83% (267/323) 2 Osteocalcium phosphate 1% (4/323) 3 Calcium pyrophosphate 15% (49/323) 4 Osteocalcin 0% (1/323) 5 Polymethylmethacrylate 1% (2/323) ML 1 Select Answer to see Preferred Response PREFERRED RESPONSE 1