APK 2105C Lecture Notes - Lecture 32: Prostaglandin E2, Rofecoxib, Cytochrome C Oxidase Subunit Ii

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Chapter 5, Lecture 2
Chemical Messengers
Classes of chemical messengers
Class
Chemical Property
Location of Receptors
on Target Cell
Functional
Classification
Amino acids
Lipophobic
Plasma membrane
Neurotransmitters
Amines
Lipophobic
Plasma membrane
Paracrines,
neurotransmitters,
hormones
Peptides/proteins
Lipophobic
Plasma membrane
Paracrines,
neurotransmitters,
hormones
Steroids
Lipophilic
Cytosol
Hormones
Eicosanoids
Lipophilic
Cytosol
Paracrines
Peptide/protein messengers
o Most chemical messengers are polypeptides
Peptide = < 50 AAs
Protein = > 50 AAs
o Hydrophilic = water soluble, not fat soluble
o Receptors located on the plasma membrane (not fat soluble)
o Synthesis and release
Synthesis is same as other proteins (transcription and translation)
Release = proteolytic enzymes in the golgi or vesicles create the final
product
mRNA goes into rough ER
Travels in lumen of rough ER
as prepropeptide
Reaches smooth ER and
breaks off into propeptide
Propeptide is taken up by
golgi apparatus
Goes through golgi until it
reaches other side and then
gets cleaved off into
secretory vesicle (propeptide
inside)
The AAs are cleaved into peptides and then released by
exocytosis
Steroid messengers
o Derived from cholesterol
o Always function as hormones
o Lipophilic
Receptors located mostly in the cytosol
Few examples of receptors on the membrane (estrogen)
o Synthesis and released
Synthesized in smooth ER or mitochondria
They are membrane permeant, they cannot be stored in cells which
secrete them—leak out of cell as soon as they’re made
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