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Lecture 6

WEEK 6.docx

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Department
Biology
Course
BIOL 103
Professor
Virginia K Walker
Semester
Winter

Description
WEEK 6: HORMONES + ENDOCRINE SYSTEM -amines and proteins/peptide hormones generally share similar chem. properties and actions; steroid hormones act differently 1. AMINES -small -water-soluble -derived from a.acid tyrosine ((nor)epinephrine) or tryptophan (melatonin) -target cell receptor on plasma membrane (except thyroid glands) -works as a secondary messenger 2. PEPTIDES/PROTEINS -small, water soluble -participates in numerous body f'ns -target cell receptor on plasma membrane -works as secondary messenger -eg. insulin, glucagon, leptin 3. STEROIDS -made from cholesterol lipids -insoluble in water -steroid hormones bound to large, soluble proteins in the blood that act as carriers -acts in cell cytosol or nucleus; stimulates gene transcription -eg. cortisol, testosterone, estradiol MEMBRANE RECEPTION -water-soluble hormones -ligand binds to a receptor protein on the plasma membrane -hormones diffuse from the blood into the interstitial fluid, binding to a specific receptor proteins on the cell surface -only cells w/ the proper receptors on their surfaces can respond to the hormone -->hormone activates only specific cells in the body -receptor interacts noncovalently + reversibly w/ hormone -initiates intracellular signalling -->1. cyclic AMP pathways --> 2. Ca2+/phosphatidylinositol pathway --> 3. tyrosine/kinase pathway -signal transduction can be rapid and involve enzymes -->enzymes can amplify the hormone signal -also leads to changes in cellular activities that occur more slowly -->usually requires activation/inhibition of various genes in the nucleus -isoforms: different receptors that can recognize the same hormone -->from different genes or alternative splicing of genes -->one hormone can perform 1+ actions in the body by binding to receptor isoforms that differ slightly from each other -->receptors have diff. affinities for the hormone: [hormone] binding affects action of cell INTRACELLULAR RECEPTION -w/ steroid hormones -receptors located within the cell (either cytosol or nucleus) -complex of steroid hormone + receptor f'ns as a transcriptional activator by binding to enhancers of a particular gene -->once bound, transcription is increased, which increases the amount of that gene's protein -single type of steroid hormone can have a variety of actions throughout the body -eg. changes in puberty [HORMONES] IN THE BLOOD -change in hormone amounts in the blood depend on: 1. changing the rate of hormone production by an endocrine 2. chang
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