Y1S2 008 II Biochem Calcium Metabolism Disorders: Overview and Functions
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Questions and Answers

What is the primary function of calcium in the development of bone and teeth?

  • Coenzyme for coagulation factors
  • Present as calcium phosphate (correct)
  • Intracellular second messenger for secretion of some hormones
  • Transmission of nerve impulses

What percentage of calcium in the plasma is protein-bound?

  • 40% (correct)
  • 20%
  • 50%
  • 30%

What is the term for the mechanism by which the body maintains adequate calcium levels?

  • Calcium metabolism
  • Calcium homeostasis (correct)
  • Calcium regulation
  • Calcium balance

What is the percentage of ionized calcium in the plasma?

<p>50% (C)</p> Signup and view all the answers

What is the role of calcium in the transmission of nerve impulses?

<p>Control of excitability (B)</p> Signup and view all the answers

What is the term for the movement of calcium between extracellular fluid, gut, bone, and kidney?

<p>Calcium balance (D)</p> Signup and view all the answers

What is the primary function of parathyroid hormone (PTH) in the body?

<p>To regulate the concentration of calcium in the ECF (B)</p> Signup and view all the answers

What is the typical location of the parathyroid glands in the body?

<p>Posterior to the thyroid gland (D)</p> Signup and view all the answers

What is the molecular weight of parathyroid hormone (PTH)?

<p>9425 Da (C)</p> Signup and view all the answers

What is the half-life of intact PTH in the blood?

<p>3-4 minutes (B)</p> Signup and view all the answers

What is the region of the PTH molecule required for PTH receptor binding in target cells?

<p>N-terminal 1-34 amino acid sequence (D)</p> Signup and view all the answers

What is the number of amino acids in the precursor molecule of PTH?

<p>115 amino acids (D)</p> Signup and view all the answers

What is the pattern of plasma PTH levels throughout the day?

<p>Highest in the early morning hours and lowest at 9 a.m. (C)</p> Signup and view all the answers

What is the primary effect of PTH on plasma [Ca2+]?

<p>Increase ionized calcium (B)</p> Signup and view all the answers

Which receptor does PTH bind to in the central nervous system?

<p>Parathyroid hormone 2 receptor (C)</p> Signup and view all the answers

What is the net effect of PTH on glomerular filtration rate (GFR)?

<p>Decrease GFR (A)</p> Signup and view all the answers

What is the result of PTH's action on the distal tubule?

<p>Increased excretion of bicarbonate (B)</p> Signup and view all the answers

What is the time frame of PTH's delayed action on bone?

<p>Days and weeks (B)</p> Signup and view all the answers

What is the primary cause of hypercalcemia in primary hyperparathyroidism?

<p>Combined effects of PTH-induced bone resorption and intestinal calcium absorption (A)</p> Signup and view all the answers

What is the most common presenting complaint in primary hyperparathyroidism?

<p>Renal stones (B)</p> Signup and view all the answers

What is the underlying mechanism of secondary hyperparathyroidism?

<p>Excessive secretion of PTH in response to hypocalcemia (A)</p> Signup and view all the answers

What is the result of the deposition of calcium in the kidney tubules in primary hyperparathyroidism?

<p>Impaired renal function (A)</p> Signup and view all the answers

What is the underlying cause of hyperphosphatemia in secondary hyperparathyroidism?

<p>Damaged renal parenchyma (C)</p> Signup and view all the answers

What is the characteristic laboratory finding in primary hyperparathyroidism?

<p>Hypercalcemia and hypophosphatemia (C)</p> Signup and view all the answers

What is the effect of 1:25-DHCC on 25-HCC?

<p>It stimulates the hydroxylation of 25-HCC (C)</p> Signup and view all the answers

What is the effect of PTH on 1α-hydroxylase activity?

<p>It stimulates the activity of 1α-hydroxylase (B)</p> Signup and view all the answers

What is the role of calbindin-D in the gut?

<p>It promotes the absorption of calcium and phosphate from the gut lumen (B)</p> Signup and view all the answers

What is the effect of calcitriol on osteoclasts?

<p>It stimulates the activity of osteoclasts (D)</p> Signup and view all the answers

What is the role of alkaline phosphatase in bone formation?

<p>It promotes the formation of new bone (A)</p> Signup and view all the answers

What is the significance of serum osteocalcin levels?

<p>They are a marker of bone formation and turnover (C)</p> Signup and view all the answers

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