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</p> Signup and view all the answers

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

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

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

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

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

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

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

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

    What is the consequence of derangements in calcium metabolism?

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

    What is the primary effect of PTH on osteoclasts?

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

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

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

    Where is the 1α-hydroxylase enzyme located?

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

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

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

    What is the effect of PTH on osteoblast activity?

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

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

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

    What is the effect of calcitriol on bone mobilization?

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

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

    <p>Hypocalcaemia</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</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</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</p> Signup and view all the answers

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

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

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