BIO 365S Lecture Notes - Lecture 3: Lipophobicity, Thyroid, Signal Transduction
Communication, Integration, and Homeostasis
Function of the cell membrane
Regulation of entrance and exit; structure support; compartment; communication
Identify as short distance communication, long distance communication or either:
•Electrical signal – long
•Neurotransmitter – short, works by diffusion
•Hormone – long
•Paracrine – short, like horoes but does’t travel to blood.
•Chemical signal – both
•Gap junction – short
Brain uses both electrical (neuron) and chemical (neurohormone) signals
Terminology Associated With Receptors
—Target cells have receptors
—Receptors have ligands
—Receptors exhibit specificity, competition, saturation; subject to allosteric modulation
—Ligand/receptor has agonists & antagonists
—Activity can be upregulared or downregulated
Specifity – only certain ones can bind
Saturation – as long as you have limited seats, your binding sites can be satured
Competition – other molecules bind to binding site and prevent ligand from binding.
Antagonists: bind and does nothing
Agonists: bind and create a response.
Upregulated: increased in activity. Cell puts more receptors up in the membrane surface.
Downregulated: decreased in activity
Signals can be:
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—Chemical or electrical
—Short distance or long distance
—Lipophilic or lipophobic
—2 major classes of receptors based on type of ligand
Cell erae’s seletie pereaility reates to lasses of ligads.
Cell membrane’s selective permeability creates two classes of ligands.
Steroids or hormones released by adrenal cortex (stress hormones) or protein hormones
released by thyroid gland (peptide hormones but behave like lipid hormones) = lipid hormones,
lipophilic
Lipophobic: meets receptor, never able to go into the cell.
Intracellular Receptors
• Cytosoli or nuclear
• Bid steroid or thyroid horoes
• At as trasriptio fators
Cell membrane Receptors
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• Are itegral erae proteis
• Bid peptide horoes & other
lipophobic signals
• Usually atiate a 2nd messenger
IC receptors can easily reach nucleus, so mostly act as transcription
factors (thyroid or steroids hormones)
Cell membrane receptors: signal cascade
Four classes of membrane receptors:
2o messengers . . .
—Transduce extracellular signal to intracellular signal à signal transduction
—Common examples: cAMP, cGMP, IP3, DAG
—Possible actions
—Trigger release of calcium from stores
—Open/close ion channels
—Modulate enzyme activity
Ability to communicate is critical for . . .
Homeostasis
Various physiologi arrageets hih sere to restore the normal state once it has been
distured
Walter Cannon ~ 1930
Body maintains at stable environment. Slight changes in chemical
response cause body to try to bring body back to normal.
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Document Summary
Regulation of entrance and exit; structure support; compartment; communication. Identify as short distance communication, long distance communication or either: electrical signal long, neurotransmitter short, works by diffusion, hormone long, paracrine short, like hor(cid:373)o(cid:374)es but does(cid:374)"t travel to blood, chemical signal both, gap junction short. Brain uses both electrical (neuron) and chemical (neurohormone) signals. Receptors exhibit specificity, competition, saturation; subject to allosteric modulation. Saturation as long as you have limited seats, your binding sites can be satured. Competition other molecules bind to binding site and prevent ligand from binding. Cell puts more receptors up in the membrane surface. 2 major classes of receptors based on type of ligand. Cell (cid:373)e(cid:373)(cid:271)ra(cid:374)e"s sele(cid:272)ti(cid:448)e per(cid:373)ea(cid:271)ility (cid:272)reates t(cid:449)o (cid:272)lasses of liga(cid:374)ds. Cell membrane"s selective permeability creates two classes of ligands. Steroids or hormones released by adrenal cortex (stress hormones) or protein hormones released by thyroid gland (peptide hormones but behave like lipid hormones) = lipid hormones, lipophilic.
