Biochemistry of Bone and Connective Tissue

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What percentage of organic material in bones is comprised of Type I collagen?

90-95% (correct)

95-98%

98-100%

80-85%

What is the primary function of osteoblasts in bone formation?

Deposition of new bone matrix (correct)

Regulation of bone density

Regulation of calcium and phosphate ions

Dissolution and resorption of bone

What is the primary component of the inorganic material in bones?

Carbonate

Magnesium

Crystalline hydroxyapatite (correct)

Sodium

What percentage of the body's calcium is contained in bones?

99% (C) Signup and view all the answers

What is the function of the proton translocating ATPase in osteoclasts?

Expelling protons across the ruffled border into resorption area (B) Signup and view all the answers

What is the function of osteocytes in bone remodeling?

Respond to mechanical strain and send signals of bone formation or resorption (C) Signup and view all the answers

What percentage of bone is remodeled each year in adult humans?

5-10% (C) Signup and view all the answers

What is the primary function of bone regarding blood cells?

Providing space for bone marrow (B) Signup and view all the answers

Which of the following hormones inhibits osteoclasts?

Calcitonin (A) Signup and view all the answers

What percentage of phosphate in our body is found in bone and teeth as hydroxyapatite crystals?

80% (A) Signup and view all the answers

What is the mature form of parathyroid hormone composed of?

84 amino acids (B) Signup and view all the answers

What is the primary function of osteoblasts?

Forming new bone tissue (D) Signup and view all the answers

What is the primary function of the Golgi apparatus in the processing of pro PTH?

To remove six amino acid residues from the N-terminal (A) Signup and view all the answers

What is the effect of PTH on phosphate levels in the urine?

Decreases phosphate reabsorption in the proximal tubules (A) Signup and view all the answers

What is the effect of PTH on Ca2+ levels in the bones?

Increases Ca2+ mobilization from bones (A) Signup and view all the answers

What is the primary regulator of PTH secretion?

Circulating ionized calcium levels (A) Signup and view all the answers

What is the effect of PTH on Ca2+ absorption from the intestine?

Increases Ca2+ absorption from the intestine (C) Signup and view all the answers

What is the effect of high plasma Ca2+ levels on PTH secretion?

Decreases PTH secretion (A) Signup and view all the answers

What is the effect of calcitonin on plasma calcium levels?

It decreases plasma calcium levels (B) Signup and view all the answers

What stimulates the secretion of calcitonin?

Beta-adrenergic agonists, Cholecystokinin, Dopamine, glucagon, estrogen, and secretin (B) Signup and view all the answers

What is the effect of calcitonin on bone resorption?

It decreases bone resorption (B) Signup and view all the answers

What is the effect of calcitonin on calcium excretion in urine?

It increases calcium excretion in urine (C) Signup and view all the answers

What is the characteristic of osteomalacia?

Deficiency of vitamin D during adulthood (A) Signup and view all the answers

What is the primary cause of osteoporosis?

Estrogen deficiency (C) Signup and view all the answers

What is the direct effect of high PO4 on vitamin D production?

It inhibits α-hydroxylase enzyme (A) Signup and view all the answers

Which of the following is NOT a function of vitamin D?

Inhibiting osteoblasts (A) Signup and view all the answers

What is the role of PTH in the formation of 1, 25 dihydroxycholecalciferol?

It facilitates the formation of 1, 25 dihydroxycholecalciferol (A) Signup and view all the answers

What is the effect of low Ca2+ on PTH secretion?

It increases PTH secretion (B) Signup and view all the answers

What is the source of vitamin D3?

Skin (D) Signup and view all the answers

What is the role of α-hydroxylase enzyme in the kidneys?

It catalyzes the formation of 1, 25 dihydroxycholecalciferol (B) Signup and view all the answers