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27 Cards in this Set

  • Front
  • Back
Class: Hormone, steroid.
Orginates from: adrenal gland. Function: affects the metabolism of proteins, carbohydrates, and lipids in most tissues.
Class: Hormone, steroid
Originates from: ovary
function: induces and maintains secondary female sexual characteristics
Class: Hormones, Alpha cells of pancreas, peptides
Originates: pancreas
Function: Stimulates glucose synthesis, glycogen breakdown, and lipid breakdown (e.g. in liver and fat cells)
Class: Hormone, Beta cells of pancreas, proteins
Originates: pancreas
Function: Stimulates uptake of glucose, protein synthesis, lipid synthesis (e.g. liver cells)
Class: Hormone, steroid
Originates: testis
Function: Induces and maintains secondary male sexual characteristics
Thyroid hormone (thyroxine)
Class: Hormone, derivate of amino acid tyorsine
Originates: Thyroid gland
Function: Stimulates metabolism of many cell types
Epidermal Growth Factor (EGF)
Class: local mediator, protein
Found in: various cells
Function: stimulates epidermal and many other cell types to proliferate
Platelet-derived growth factor (PDGF)
Class: local mediator, protein
Found in: various cells including blood platelets
Function: stimulates cell proliferation
Nerve Growth Factor (NGF)
Class: local mediator, protein
Found in: various innervated tissues
Function: promotes survival of certain classes of neurons, promotes growth of their axons.
Transforming growth factor-Beta (TGF-Beta)
Type: local mediator, protein
Found in: many cell types
Function: inhibits cell proliferation, stimulates extracellular matrix production
Type: local mediator, derivative of histidine
Found in: mast cells (part of immune system), and many other cell types
Function: causes blood vessels to dilate and become leaky, helping to cause inflamation
Nitric Oxide
Type: local mediator, dissolved gas made from arginine. quickly converted to nitrates and nitriles (half life ~5-10 seconds)when it reacts with water and oxygen.
Found in: endothelial cells lining blood vessels, nerve cells
Function: causes smooth muscle cells to relax, can regulate blood pressure, regulates nerve cell activity.

Inside many target cells binds to enzyme guanalyl cyclase, stimulating formation of cyclic GMP
Type: neurotransmitter, derivative of choline
Found in: nerve terminals, nerve-muscle synapses and in central nervous system.
Function: When a heart muscle is exposed to it the rate and force of contractions decrease, but when a salivary gland is exposed to it, it secretes components of saliva. Binds to a different type of receptor protein for skeletal muscle cells and causes contraction.
γ-Aminobutyric acid (GABA)
Type: neurotransmitter, derivative of glutamic acid
Found in: nerve terminals
Function: inhibitory neurotransmitter in central nervous system. Binds to channel for Cl-. When bound, very little Cl- enters cell (low electrochemical potential)
Type: Contact-dependent signal molecules
Originates in: prospective neurons
Found in: transmembrane protein, found in prospective neurons and various other developing cell types
Function: inhibits neighboring cells from becoming specialized in same way as signaling cell.
cyclic GMP
NO binds to guanyl cyclase stimulating cyclic GMP formation from nucleotide GTP.

small intracellular signaling molecule that forms next link in signaling chain that leads to the cell's ultimate response. Viagara enhances penile erection by blocking the degradation of cyclic GMP, prolonging the NO signal. Very similar to structure and mechanism of cyclic AMP
G-Protein-linked receptors
activate a class of membrane-bound protein (a trimeric GTP-binding protein, or G-protein) which is then released to migrate in the plane of the plasma membrane, initiating a cascade of other effects. A class of GTP-binding protein.
Enzyme linked receptors:
when activated, act as enzymes or are associated with enzymes inside the cell. Switching on this enzymatic activity then generates a host of additional signals, including small molecules that are released into the cytosol.
Ion-Channel linked receptors
covert chemical signals into electrical ones (also known as transmitter-gated ion channels).
These receptors are responsible for transduction of a chemical signal in the form of a pulse of a neurotransmitter delivered to the outside of the target cell directly into an electrical signal, in the form of a change in voltage across the target cell’s plasma membrane.
intracellular signaling proteins:
act as molecular switches. apart from a few small molecules like cyclic GMP, cyclic AMP, and Ca2+, intracellular signaling molecules are proteins. Some serve as chemical transducers and others as messengers.
2 categories:
1)proteins turned on or off by phosphorylation
2)GTP-binding proteins
protein kinase
controlls switch proteins by phospohorylating them. are often organized into phosphorylation cascades (and act as signaling proteins themsmelves)
protein phosphatase
removes the phosphate group from an intracellular switch protein. also can be incorporated into the phosphorylation cascade and act as a signaling protein itself.
GTP-binding proteins
switch between active and inactive. A GTP-binding signaling protein is induced to exchange its bound GDP for GTP, which activates the protein; hydrolysis of the bound GTP to GDP then switches the protein off.
phosphorylation cascades
one protein kinase, activated by phosphorylation, phosphorylates the next protein kinase in the sequence, and so on, transmitting the signal onward and in the process amplifying, distributing, and modulating it.
structure of G-protein-linked receptors
Each G-protein linked receptor is made of a single polypeptide chain that threads back and forth across the lipid bilayer 7 times.

G proteins composed of three protein subunits, α, β, γ tethered to the plasma membrane by short lipid tails. In the unstimulated state, the α subunit has GDP bound to it and the G protein is idle. When an extracellular ligand binds to its receptor, the altered receptor activates a G protein by causing the α subunit to lose some of its affinity for GDP, which it exchanges for a molecule of GTP. This activation breaks up the subunits: the “switched on” α subnit, clutching its GTP detaches from the βγ complex, giving rise to two separate molecules that now roam independently along the plasma membrane. The two activated parts of a G protein can both interact directly with target proteins located in the plasma membrane, which in turn may relay the signal to yet other destinations. The longer the target proteins have a subunit attached to them the stronger and more prolonged the relayed signal will be.
the light-activated photoreceptor protein in the vertebrate eye. a type of G-protein linked receptor. (7 pass transmembrane protein)
α subunit
has an intrinsic GTP-hydrolyzing (GTPase) activity, and it eventually hydrolyzes its bound GTP back to GDP; the α subunit then reassociates with the βγ complex and the signal is shut off.