More questions on calcium

1.  For each of the following, give a definition, which includes its location and function.  Be specific, but concise.  That is, a one-sentence answer is all you need, but that one sentence should include the relevant information. (10 pts each) 

A.  Chondrocytes

B.  1-alpha hydroxylase

C.  Calcium-sensing receptor

D.  Melanocytes

E.  C-cells

2.   In the 1960ís and 70ís, gasoline contained lead, and when cars burned it, lead got in the air, and into those of us who were inhaling at that time.  Fortunately, lead is like calcium in its ability to be deposited in bones, so the lead that got into our body is sequestered in our bones, not circulating around in the blood where it could damage tissues.  Unfortunately, when women become pregnant, bone may be broken down to provide calcium for building the bones of the fetus.  When the motherís bone is broken down, both the calcium and the lead will be released to the blood.  The lead can reach the fetus and may damage its developing nervous system.  The best way to treat the pregnant mother would be to give her

a.  an increase in calcium in the diet 
b.  a drug that blocks calbindin synthesis
c.  a drug that blocks calcitonin synthesis
d.  a drug that stimulates PTH secretion
e.  injection of growth hormone

Choose the best one, and explain how that treatment would work to relieve the problem.  Your answer should include the events that would be affected on a cellular level.  (30 pts)

 

 

ANSWERS

1.  For each of the following, give a definition, which includes its location and function.  Be specific, but concise.  That is, a one-sentence answer is all you need, but that one sentence should include the relevant information. (10 pts each) 

A.  Chondrocytes

Cells dispersed in cartilage.  Secrete collagen to form the matrix of collagen, and to produce new cartilage.

B.  1-alpha hydroxylase

 An enzyme found in the kidney.  Functions to convert 25-OH Vitamin D to 1, 25-OH Vitamin D (calcitriol), and so functions to produce the active Vitamin D.

C.  Calcium-sensing receptor

Found on the membrane (7-pass protein) of parathyroid cells.  Functions to maintain blood calcium levels, by secreting parathyroid hormone in response to low blood calcium concentrations.

D.  Melanocytes

Found in the epidermis of the skin, just above the dermis.  Synthesize melanin pigment and transfer it to the overying keratinocytes, thereby protecting the underlying cell from ultraviolet light.

E.  C-cells

Found between the follicles of the thyroid gland.  Secrete calcitonin, which can lower blood calcium levels. 

2.   In the 1960ís and 70ís, gasoline contained lead, and when cars burned it, lead got in the air, and into those of us who were inhaling at that time.  Fortunately, lead is like calcium in its ability to be deposited in bones, so the lead that got into our body is sequestered in our bones, not circulating around in the blood where it could damage tissues.  Unfortunately, when women become pregnant, bone may be broken down to provide calcium for building the bones of the fetus.  When the motherís bone is broken down, both the calcium and the lead will be released to the blood.  The lead can reach the fetus and may damage its developing nervous system.  The best way to treat the pregnant mother would be to give her

a.  an increase in calcium in the diet (10 points)
b.  a drug that blocks calbindin synthesis
c.  a drug that blocks calcitonin synthesis
d.  a drug that stimulates PTH secretion
e.  injection of growth hormone

Choose the best one, and explain how that treatment would work to relieve the problem.  Your answer should include the events that would be affected on a cellular level.  (30 pts)

The goal is to prevent bone breakdown.  An increase in dietary calcium will mean that there is more calcium available to be absorbed.  (Note:  About 30% of dietary calcium is absorbed.  If you take in 100 mg, about 30 mg is absorbed. If you take in 1000 mg, about 300 mg is absorbed.  Perhaps you'd like to treat this woman with Vitamin D, too, to absorb even more.)  This would relieve the problem, because if blood calcium is always high, then the calcium-sensing receptor of the parathyroid gland will not signal for more PTH to be released. (10) PTH usually binds receptors on the osteoblast membrane, and the osteoblasts secrete a cytokine that stimulates an increase in osteoclast activity.  The osteoclasts then secrete acid and proteolytic enzymes on the surfaces of bones, causing them to break down.(10)  So when Ca++ is high in the blood, there would be less PTH secreted, and less bone breakdown.