B6.052 Prework 2: Cell Biology of Bone

Question 1

composition of bone matrix

Answer 1

fibers + ground substance (not cells)
organic matrix (35%)
inorganic salts (65%)

Question 2

organic matrix components of bone

Answer 2

proteins, glycoproteins, and proteoglycans synthesized by osteoblasts
type 1 collagen fibers

Question 3

inorganic content of bone

Answer 3

hydroxyapatite crystal
Ca10(PO4)6(OH2)
^^calcium phosphate salt

Question 4

osteoprogenitor cells

Answer 4

pluripotent stem cells with mesenchymal origin
capable of differentiating into osteoblasts
found in periosteum and endosteum and bone lining cells in non growing regions

Question 5

osteoblasts

Answer 5

synthesize and secrete the organic matrix of bone: collagenous and non-collagenous proteins and alk phos that initiates calcification

Question 6

osteocytes

Answer 6

osteoblasts that are trapped in calcified matric

alive and play a role in bone maintenance and metabolism

Question 7

osteoclasts

Answer 7

giant, multinucleate cells derives from monocytes
produce acidic environment ideal for dissolution of bone matrix
cell membrane is folding to create villous like processes of the ruffled border

Question 8

what do osteoblasts synthesize

Answer 8

osteoid
alk phos
non collagenous proteins

Question 9

osteoid

Answer 9

type 1 collagen + proteoglycans

Question 10

alk phos

Answer 10

on surface of bone

initiates calcification by increasing the local Ca:PO4 ratio

Question 11

noncollagenous proteins

Answer 11

RANK-L
osteoprotegerin
osteocalcin
osteopontin
bone sialoproteins
growth factors

Question 12

RANK-L

Answer 12

receptor activator of NFKB ligand

simulates osteoclastogenesis

Question 13

osteoprotegerin

Answer 13

decoy receptor for RANK-L

Question 14

osteocalcin

Answer 14

required for mineralization

Question 15

osteopontin

Answer 15

formation of sealing zones

Question 16

growth factors in bone

Answer 16

bone morphogenetic proteins (BMPs)

members of the TGFB family

Question 17

functions of osteocytes

Answer 17

assist in maintenance of Ca and PO4 levels in the blood
osteocytic osteolysis (resorption) and osteoid production (deposition) primarily in maintenance of blood Ca level
stress sensors, mechanotransduction
synthesize sclerostin

Question 18

sclerostin

Answer 18

inhibits osteoblastic activity

Question 19

function of mitochondrial in osteoclasts

Answer 19

drive production of hydrolytic enzymes