Chapter 16 Cell communication part 1

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iishvo
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251798
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Chapter 16 Cell communication part 1
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2013-12-08 21:16:17
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cell communcation
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ch 16 cell bio davis
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  1. Types of cellular communcation
    • endocrine
    • paracrine
    • neuronal and
    • contact dependent
  2. endocrine
    involves hormones in the bloodstream
  3. paracrine
    local mediators
  4. Hormone List
    • Adrenaline
    • cortisol
    • estradiol
    • glucagon
    • insulin
    • testosterone
    • thyroid hormone (thyroxine)
  5. Adrenaline (epinephrine)
    adrenal gland, derivative of amino acid tyrosine, increases bp, hr, and metabolism
  6. cortisol
    adrenal gland, steroid (derivative of cholesterol), affects metabolism of proteins, carbohydrates, and lipids in most tissues
  7. estradiol
    ovary, steroid (derivative of cholesterol). induces and maintains secondary female sexual characteristics
  8. glucagon
    alpha cells of pancreas,peptide, stimulates glucose synthesis, glycogen breakdown and lipid breakdown in lipid and fat cells
  9. insulin
    beta cells of pancrease, protein, stimulates glucose uptake, protein synthesis, and lipid synthesis in liver cells
  10. testosterone
    testis, steroid (derivative of cholesterol), induces and maintains secondary male sexual characteristics
  11. thyroid hormone (thyroxine)
    thyroid gland, derivative of amino acid tyrosine, stimulates metabolism of many cell types
  12. Small/polar molecules and most peptide/protein hormones have specific receptors where?
    on the outer plasma membrane
  13. Steroid hormones
    • penetrate the membrane
    • receptors are on/inside the nucleus
    • site of action is in the nucleus
  14. steroid responsive elements (SREs)
    some steroids bind to proteins that are directly bound to DNA which free up genes for fast transcription/translation
  15. Local mediators list
    • epidermal growth factor (EGF)
    • platelet-derived growth factor (PDGF)
    • nerve growth factor (NGF)
    • transforming growth factor beta (TGF-B)
    • histamine
    • nitric oxide
  16. epidermal growth factor
    various cells, protein, stimulates epidermal and many other cell types to proliferate
  17. platelet-derived growth factor
    various cells, including blood platelets, protein, stimulates many cell types to proliferate
  18. nerve growth factor
    various innervated tissues, protein, promote survival of certain classes of neurons to promote growth of their axons
  19. transforming growth factor
    many cell types, protein, inhibits cell proliferation and stimulates extracellular matrix production
  20. histamine
    mast cells, derivative of the amino acid histidine, causes blood vessels to dilate and become leaky, helping to cause inflammation
  21. nitric oxide
    nerve cells; endothelial cells lining blood vessels, dissolved gas, causes smooth muscle cells to relax, regulates nerve cell activity
  22. Neurotransmitters list
    • acetylcholine
    • gama-aminobutyric acid (GABA)
  23. acetylcholine
    nerve terminals, derivative of choline, excitatory neurotransmitters at many nerve muscle synapses and in central nervous system
  24. GABA
    nerve terminals, derivative of the amino acid glutamic acid, inhibitory neurotransmitter in central nervous system
  25. contact dependent signal molecule
    delta -> site of origin is prospective neurons and various other developing cell types, chemical nature is transmembrane proteins, and inhibits neighboring cells from becoming specialized in same way as the signaling cell
  26. local mediators
    exert their effect in the environment directly surrounding their release:
  27. most effective local mediator is
    prostaglandins
  28. 2 major factors as to diversity of responses to the same ligand
    • 1)different receptor subclasses- ex. serotonin has at least 7 different receptors spread over multiple cell types
    • 2) even the same receptor subclass can produce different responses in different cell types due to differences in the molecular machinery that it is linked to
  29. Multiplicity of signals from different ligands can
    • produce varying effects
    • makes great versatility and variety of responses but unfortunately it makes it hard to decipher signal pathways
    • best we can do is look at individual pathways and try to piece together
    • computer analysis is best way
  30. fast responses
    • pathways that have premade mediators, second messengers, etc.
    • if all pieces are readily available then cell can respond rapidly
  31. fast response example
    ex. mast cells responsible for allergic reaction have pre-loaded granules that are filled with histamine and TNF-alpha. cross linking of surface IgE with allergens causes immediate granule fusion with plasma membrane and degranulation; mediators are dumped out into tissues
  32. Slow response
    • pathways require protein synthesis to produce effects that take longer
    • must allow time for transcription and translation
  33. thyroxine
    • produced in thyroid gland in response to thyroid stimulating hormone produced by the pituitary gland in the brain
    • exist in two forms:
    • 1) T3 which has 3 iodines
    • 2) T4 which hasĀ  iodines, and is absolutely essential to maintenance of the overall metabolic rate, low levels lead to severe chronic fatigue; over sensitivity to cold temperatures is a big tip off
  34. Cortisol mode of action
    • passes the plasma membrane and binds to nuclear receptor protein which is activated by cortisol binding.
    • ligand~receptor complex is routed to nucleus where it binds to the regulatory regions of target genes
    • acts as a transcription switch
  35. role of nitric oxide (NO)
    • NO is synthesized andĀ released from Arg when ACh binds to vascular endothelial cell receptors
    • NO can easily pass membranes to smooth muscles lining the blood vessels, it then binds to specific proteins that regulate muscle tone which cause vasodilation
    • signal doesn't last long since NO transforms to nitrate and nitrite ion
  36. second messengers
    • small molecules that spread and amplify the signal inside the cell
    • can affect other systems such as kinases and phosphatases
    • have multitude of effects on different proteins that play key roles in metabolism, cell shape/movement, or gene expression
  37. Intracellular "molecular switches"
    • 1) protein phosphorylation by kinases activates otherwise inactive enzymes that perform catalysis. phosphorylation turns enzymes "on".
    • 2) g-protein coupled receptors take a round-about way of signaling. not as direct, but equally specific based on receptor to which they are coupled
  38. Diversity in receptor types:
    • 1) ion channel-coupled receptors which bind ligands to specific sites and this opens the channel due to conformational changes
    • 2) g-protein coupled receptors (and g protein themselves) are anchored in the membrane. ligand binding induces a change in g-protein conformation such that GDP is exchanged for GTP; it can activate other proteins
    • 3)enzyme-coupled receptors can be composed of dimers that are cross-linked by ligand to form the active form; or a single ligand can induce union of two parts, which then activate a target enzyme
  39. Valium and barbituates
    gaba signal molecule, gaba antagonist, relief of anxiety and sedation
  40. nicotine
    AcH, AcH agonist, constriction of blood vessels and elevation of blood pressure
  41. morphine and heroin
    endorphins and enkephalins, g-protein coupled opiate receptors, analgesia (relief of pain) and euphoria
  42. Curare
    AcH, AcH antagonist, blocks neuromuscular transmission, resulting in paralysis
  43. Strychnine
    glycine, glycine antagonist, blocks inhibitory synapses in spinal and brain resulting in seizures and muscle spasms
  44. agonists
    ligands that bind to and activate the receptor
  45. antagonists
    bind to receptor and prevent ligand binding
  46. G-protein actions
    • stimulatory or inhibitory
    • 3 subunits: alpha, beta, and gamma
    • a subunit binds GDP in its inactive form and binding of ligand by an associated receptor results in exchange of GDP for GTP. No GTP hydrolysis just a transfer
  47. G proteins can
    • induce production of 2nd messengers such as cAMP
    • if target protein is adenyl cyclase then ATP -> cAMP
    • cAMP is then set free in the cytosol and activates multiple targets. this results in amplification of responses
  48. cell responses and signal molecules mediated by cyclic AMP
    adrenaline, ACTH, and glucagon
  49. Adrenaline
    • targets heart tissue to increase HR and FOC
    • targets skeletal muscle for glycogen breakdown
  50. Adrenaline, ACTH, glucagon
    targets fat to breakdown fat
  51. ACTH
    targets adrenal gland for cortisol secretion
  52. Phosphdiesterase
    continually converts cAMP to AMP, so the system doesn't run away with itself. makes continuous or repeated stimulation necessary for a sustained response
  53. cAMP is a major activator of
    several classes of kinases
  54. once adrenaline binds to its receptors...
    • it activates a Gs alpha subunit that activates adenyl cyclase -> cAMP -> activation of protein kinase A (PKA) -> PKA then activates phosphorylase kinase
    • because two kinases are activated a phosphorylase is then activated and the end effect is glycogen breakdown to glucose for quick access to energy
  55. How does cAMP effect gene transcription?
    PKA passes into the nucleus and phosphorylates a transcription factor

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