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

Which of the following hormones plays a minor role in maintaining calcium concentration in the extracellular fluid?

  • Parathyroid hormone (PTH)
  • Calcitriol
  • Insulin
  • Calcitonin (correct)

What percentage of calcium in the plasma is present in the ionized form?

  • 50% (correct)
  • 80%
  • 40%
  • 10%

What is the total weight of parathyroid tissue in the human body?

  • 500 mg
  • 250 mg
  • 150 mg (correct)
  • 1000 mg

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

<p>Structural function (B)</p> Signup and view all the answers

How many amino acids are present in the intact PTH molecule?

<p>84 amino acids (A)</p> Signup and view all the answers

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

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

What percentage of protein-bound calcium is bound to albumin?

<p>80% (D)</p> Signup and view all the answers

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

<p>Calcium homeostasis (C)</p> Signup and view all the answers

Which part of the PTH molecule is necessary for PTH receptor binding in target cells?

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

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

<p>Acute regulation of plasma calcium levels (A)</p> Signup and view all the answers

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

<p>Neuromuscular function (C)</p> Signup and view all the answers

What is the consequence of derangements in calcium metabolism?

<p>Either hypercalcemia or hypocalcemia (D)</p> Signup and view all the answers

What is the primary effect of PTH on osteoclasts?

<p>Stimulating their development (D)</p> Signup and view all the answers

What is the primary role of 25-hydoxylase in vitamin D metabolism?

<p>Converting cholecalciferol to calcidiol (C)</p> Signup and view all the answers

What is the net result of PTH's actions on bone and calcium levels?

<p>Increased plasma calcium levels (C)</p> Signup and view all the answers

Where is the 1α-hydroxylase enzyme located?

<p>Proximal convoluted tubules of the nephrons (B)</p> Signup and view all the answers

What is the role of vitamin D-binding protein in vitamin D metabolism?

<p>Transporting vitamin D (C)</p> Signup and view all the answers

What is the effect of PTH on osteoblast activity?

<p>Slowly stimulating osteoblast activity (A)</p> Signup and view all the answers

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

<p>It stimulates the conversion of 25-HCC to 24:25-DHCC (A)</p> Signup and view all the answers

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

<p>It directly stimulates the activity (C)</p> Signup and view all the answers

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

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

What is the effect of calcitriol on bone mobilization?

<p>It stimulates bone mobilization (A)</p> Signup and view all the answers

What is the role of osteocalcin in bone formation?

<p>It is a marker of bone formation and turnover (D)</p> Signup and view all the answers

What is the effect of calcitriol on alkaline phosphatase production?

<p>It stimulates the production of alkaline phosphatase (A)</p> Signup and view all the answers

What is the primary stimulus for PTH release in secondary hyperparathyroidism?

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

What is the result of end-organ resistance to parathyroid hormone in secondary hyperparathyroidism?

<p>Decreased mobilization of calcium from the bones (D)</p> Signup and view all the answers

What is the effect of increased intracellular phosphate on the 1-hydroxylase enzyme in end-stage renal failure?

<p>It inhibits the activity of the 1-hydroxylase enzyme (A)</p> Signup and view all the answers

What is the result of reduced normal renal tissue in end-stage renal failure?

<p>Reduced capacity for 1:25-DHCC synthesis (B)</p> Signup and view all the answers

What is the consequence of hypocalcaemia in end-stage renal failure?

<p>Increased release of PTH (C)</p> Signup and view all the answers

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