Biology Forums - Study Force

Which hormone below targets osteoclasts when blood calcium levels are too low, thus, causing an increase in the concentration of calcium in the blood
 
  a. aldosterone.
  b. thyroid hormone.
  c. cortisol.
  d. parathyroid hormone.
  e. calcitonin.

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(Question 2) What happens to most of the secreted T4?
 
  a. it is phagocytized by target tissues.
  b. it is converted into T3 after being peripherally stripped of one of its I atoms.
  c. it is the major biologically active form of thyroid hormone at the cellular level.
  d. it is split to form two DIT molecules, which are excreted in the urine.
  e. it is permitted to exert its full biological effect as a result of epinephrine's permissive actions.

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(Question 3) During thyroid hormone secretion,
 
  a. the follicular cells phagocytize a piece of colloid.
  b. T4 and T3 are split off of thyroglobulin by lysosomal enzymes within the follicular cell and subsequently diffuse out of the cell into the blood.
  c. T4 and T3 are secreted by exocytosis of the colloid that has been internalized by the follicular cells.
  d. both (a) and (b) above.
  e. both (a) and (c) above.

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(Question 4) The iodine pump refers to the
 
  a. mechanism whereby target cells extract iodine-containing thyroid hormone from the blood.
  b. active transport mechanism that concentrates iodine in the thyroid.
  c. mechanism whereby T3 and T4 are released from thyroglobulin and pumped into the circulation.
  d. protein binding process whereby T3 and T4 are pumped throughout the body bound to plasma proteins.
  e. mechanism whereby ingested iodine is absorbed by the small intestine.

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(Question 5) Thyroxine (T4)
 
  a. is formed by coupling one MIT and one DIT within the colloid.
  b. is produced by the C cells of the thyroid gland.
  c. exerts a calorigenic effect.
  d. inhibits thyroid-stimulating immunoglobulin in negative-feedback fashion.
  e. is more potent than tri-iodothyronine.

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(Question 6) About 90 of the secretory product released from the thyroid gland is in the form of
 
  a. T3
  b. T4
  c. MIT
  d. DIT
  e. TSH

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(Question 7) Which of the following statements concerning the synthesis and storage of thyroid hormones is incorrect?
 
  a. the iodine pump of the follicular cells is important for thyroid hormone production.
  b. thyroid hormones are formed within a much larger molecule called thyroglobulin.
  c. thyroid-hormone synthesis is greatly stimulated by the presence of TSH.
  d. a one- to two-hour supply of thyroid hormone is stored within the colloid in the lumen of the follicle.
  e. the coupling of two DIT molecules yields thyroxine.

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(Question 8) Which biochemical event does not take place within during thyroid hormone synthesis?
 
  a. one monoiodotyrosine molecule combines with one diiodotyrosine molecule to form one triiodothyronine molecule.
  b. two iodine molecules combine with one tyrosine molecule to form one diiodotyrosine molecule.
  c. two diiodotyrosine molecules combine to form one molecule of thyroxine.
  d. four iodine molecules combine with one tyrosine molecule to form one tetraiodothyronine molecule.
  e. all of these answers.

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(Question 9) Hormones produced by the thyroid include
 
  a. calcitonin.
  b. thyroxine.
  c. triiodothyronine.
  d. both (a) and (b) above.
  e. all of these answers.

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(Question 10) Thyroid hormones
 
  a. are derivatives of an amino acid.
  b. are produced from tyrosine.
  c. are stored on thyroglobulin within the follicular colloid.
  d. both (a) and (c) above.
  e. all of these answers.

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