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 3 1 2 3 Previous Next You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ13.119) Which of the following components of bone is most responsible for compressive strength? Review Topic | Tested Concept QID: 4754 Type & Select Correct Answer 1 Type I collagen 38% (1690/4483) 2 Osteocalcin 20% (900/4483) 3 Proteoglycans 38% (1692/4483) 4 Osteonectin 2% (110/4483) 5 Osteopontin 1% (66/4483) L 5 Question Complexity B Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 3 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ08.13) All of the following are true regarding osteocalcin EXCEPT which of the following? Review Topic | Tested Concept QID: 399 Type & Select Correct Answer 1 It is the most prevalent non-collagenous protein in bone 18% (369/2105) 2 It is expressed by mature osteoblasts 11% (235/2105) 3 It is considered a marker for osteoblast differentiation 12% (263/2105) 4 It is a glycoprotein that binds calcium 39% (812/2105) 5 Higher levels are correlated with increases in bone mineral density during osteoporosis treatment 19% (409/2105) L 4 Question Complexity C Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 4 You have 100% on this question. Just skip this one for now. Take This Question Anyway (OBQ05.138) All of the following statements are true of osteocalcin EXCEPT: Review Topic | Tested Concept QID: 1024 Type & Select Correct Answer 1 It is the most abundant noncollagenous protein of bone 8% (127/1580) 2 It is secreted by osteoclasts 69% (1087/1580) 3 It is involved in mediating calcium homeostasis 8% (131/1580) 4 It has been used as a biochemical marker of bone formation 7% (105/1580) 5 It is part of the organic matrix of bone 8% (120/1580) L 2 Question Complexity D Question Importance Select Answer to see Preferred Response SUBMIT RESPONSE 2