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Endocrine System: Biochemistry, Secretion and Transport of Hormones

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Endocrine System: Biochemistry, Secretion and Transport of Hormones

1. Place the following hormones into one of the three categories of hormones (peptides, amines or steroids): T4 (thyroxin), estradiol, norepinephrine, insulin, aldosterone, glucagon, cortisol, growth hormone, T3 (triiodothyronine), epinephrine, testosterone and vasopressin (ADH).

Peptides Amines Steroids


2. Peptide hormones are synthesized as large precursor hormones called PREPROHOMONES. The hormones (or prohormones) are stored in AMINO ACIDS and released from the cell by VESICLES. Do peptide hormones require a carrier in the blood stream? NO, PEPTIDE HORMONES CAN TRAVEL THE BLOODSTREAMS WITHOUT A CARRIER.

3. Catecholemines are produced in the ADRENAL MEDULLA of the adrenal gland and are classified as PEPTIDE hormones since they are derived from TYROSINE. Stimulation of the chromaffin cells causes an influx of RECEPTOR-MEDIATED ions, which causes the vesicles to merge with the plasma membrane and release the hormone by CHROMAFFIN CELLS. Are catecholemines water-soluble or lipid-soluble? CATECHOLEMINES ARE WATER-SOLUBLE.

4. Thyroid hormones include two molecules called T3 and T4. T3 consists of two TYROSINE molecules plus THREE iodine molecules and is LESS abundant than T4. Are carriers required for the transport of thyroid hormones? YES, CARRIERS ARE REQUIRED FOR THE TRANSPORT OF THYROID HORMONES.

5. All steroid hormones are derived from CHOLESTEROL, which steroid hormone is produced is determined by the ENZYMES present in the cell. The common precursor molecule for all steroid hormones is PREGNENOLONE. Steroid hormones enter the blood stream by DIFFUSION and DO require a carrier. The rate of secretion


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