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Questions and Answers
Which of the following hormones are considered eicosanoids?
Which of the following hormones are considered eicosanoids?
What characterizes glycoprotein hormones?
What characterizes glycoprotein hormones?
Which amino acid derivatives are known to form certain hormones?
Which amino acid derivatives are known to form certain hormones?
What type of hormones are classified as short chain peptides?
What type of hormones are classified as short chain peptides?
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Which statement about lipid-derived hormones is true?
Which statement about lipid-derived hormones is true?
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What is the primary precursor for the synthesis of steroid hormones?
What is the primary precursor for the synthesis of steroid hormones?
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How are protein/peptide hormones primarily released from cells?
How are protein/peptide hormones primarily released from cells?
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Which organelle is primarily involved in the post-translational modification of hormones?
Which organelle is primarily involved in the post-translational modification of hormones?
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What characterizes steroid hormones in terms of storage in cells?
What characterizes steroid hormones in terms of storage in cells?
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What property allows steroid hormones to cross cell membranes more easily than protein hormones?
What property allows steroid hormones to cross cell membranes more easily than protein hormones?
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Which of the following steps is NOT part of protein/peptide hormone synthesis?
Which of the following steps is NOT part of protein/peptide hormone synthesis?
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Which statement correctly describes how protein hormones are stored in the body?
Which statement correctly describes how protein hormones are stored in the body?
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What is a characteristic of the chemical structure of steroid hormones?
What is a characteristic of the chemical structure of steroid hormones?
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What role do enzymes located in mitochondria and smooth ER play in hormone synthesis?
What role do enzymes located in mitochondria and smooth ER play in hormone synthesis?
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At which phase of protein hormone synthesis does the primary RNA transcript occur?
At which phase of protein hormone synthesis does the primary RNA transcript occur?
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Study Notes
Hormone Classification
- Hormones are classified by their proximity to the site of action (autocrine, paracrine, endocrine, neuroendocrine, pheromones) and by their chemical structure (proteins/peptides, steroids, amino acid derivatives, eicosanoids).
- Solubility in aqueous media dictates how hormones are transported (hydrophobic or hydrophilic).
Hormone Derivatives of Tyrosine and Tryptophan
- Hormones are derived from amino acids tyrosine and tryptophan, and exist in various forms.
- L-tryptophan is a precursor and leads to the production of 5-hydroxytryptophan.
- 5-hydroxytryptophan is converted to serotonin.
- Serotonin is then converted by N-acetyltransferase (NAT) to N-acetylserotonin which is later converted to melatonin.
Hormone Derivatives of Tyrosine
- Tyrosine is a precursor to several important hormones like dopamine, noradrenaline, and adrenaline.
- These hormones are derived from tyrosine via enzymatic reactions (Aromatic Amino Acid Decarboxylase (AAD) and Dopamine beta-hydroxylase (DBH) and Phenylethanolamine-N-methyltransferase (PNMT)).
Peptide/Protein Hormones
- Peptide hormones include shorter chain peptides, larger proteins, and glycoproteins.
- Oxytocin is a peptide hormone.
- Growth hormone is a protein hormone.
- Examples of glycoprotein hormones are TSH, LH, EPO, hCG, and Inhibin.
Lipid Derived Hormones
- Cholesterol is the precursor of steroid hormones, which are a class of lipid-derived hormones.
- Gonadal steroid hormones include androgens (testosterone), estrogens (estradiol), and progestins (progesterone).
- Adrenocortical steroid hormones include glucocorticoids (cortisol), mineralocorticoids (aldosterone).
- Eicosanoids are lipid mediators derived from arachidonic acid, including prostaglandins (PGs), thromboxanes, and leukotrienes.
Chemical Structure Determines
- A hormone's chemical structure dictates its synthesis, storage, release, transport within the body, receptor location, mechanism of action, and degradation.
Hormone Synthesis and Storage
- Protein/peptide hormones are synthesized through a multi-step process involving transcription, translation, and post-translational modifications.
- These hormones are stored in vesicles until needed.
- Release occurs through exocytosis
- The bi-lipid membrane doesn't allow these hormones to pass through so they need exocytosis.
Synthesis of Insulin
- Insulin is a protein hormone created through several steps, starting with preproinsulin which becomes proinsulin and then finally to insulin.
Multiple Processing Patterns for Protein Hormones
- Preprohormones undergo processing to form the final active hormone and other fragments.
- Pro-opiomelanocortin (POMC) is an example of a prohormone that produces various hormones/fragments
Steroid Hormones
- Steroid hormones are derived from cholesterol.
- Enzymes in mitochondria and smooth endoplasmic reticulum (ER) are essential in the synthesis process.
- Steroid hormones are immediately released and are not packaged.
- These hormones are highly lipid-soluble and readily cross cell membranes.
Major Pathways in Steroid Biosynthesis
- Specific enzymes (like CYP17, 3β-HSD, CYP21A2, CYP11B1, CYP11B2) catalyze various steps in the conversion of cholesterol to different steroid hormones.
- Pathways lead to steroid hormones like cortisol, aldosterone, estrogens, and androgens.
Steroids can be transformed to active steroid in target cell
- Steroids can go through transformations in the target cell in order to become an active steroid hormone.
Protein/Peptide vs Steroid Secreting Cells
- Protein/peptide secreting cells have a different structure than steroid secreting cells.
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Description
Explore the classification of hormones based on their proximity to action and their chemical structure. Learn about the derivatives of tyrosine and tryptophan, including the conversion processes leading to vital hormones like serotonin and melatonin.
