Still busy
Labels: Failsafe diary
Dietary Bloggery
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Anxiety, Challenges, Dairy, Failsafe diary, Hunger, Hypoglycemia
Labels: Dairy, Failsafe diary, Hunger
Labels: Dairy, Failsafe diary
Labels: Optimal Diet, Protein
Labels: Epsom Salts, Failsafe diary, MSG
Labels: Failsafe diary, MSG
Labels: Failsafe diary
Labels: Failsafe diary, Grains, Unusual Reactions
Labels: Exercise, Failsafe diary, Grains, Moods
Labels: Failsafe diary, Holidays
Labels: Failsafe diary, Hypoglycemia, Moods
Sweet substances (like table sugar — sucrose) bind to G-protein-coupled receptors (GPCRs) at the cell surface.
- Each receptor contains 2 subunits designated T1R2 and T1R3 and is
- coupled to G proteins.
- The complex of G proteins has been named gustducin because of its similarity in structure and action to the transducin that plays such an essential role in rod vision.
- Activation of gustducin triggers a cascade of intracellular reactions:
--- activation of adenylyl cyclase
--- formation of cyclic AMP (cAMP)
--- the closing of K+ channels that leads to depolarization of the cell.
- The mechanism is similar to that used by our odor receptors.
The hormone leptin inhibits sweet cells by opening their K+ channels. This hyperpolarizes the cell making the generation of action potentials more difficult. Could leptin, which is secreted by fat cells, be a signal to cut down on sweets?
Bitter
The binding of substances with a bitter taste, e.g., quinine, phenyl thiocarbamide [PTC], also takes place on G-protein-coupled receptors that are coupled to gustducin. In this case, however, cyclic AMP acts to release calcium ions from the endoplasmic reticulum, which triggers the release of neurotransmitter at the synapse to the sensory neuron. Humans have at least two dozen genes ("T2Rs") encoding different bitter receptors. However, each taste cell responsive to bitter expresses many of these genes. (This is in sharp contrast to the system in olfaction where a single odor-detecting cell expresses only a single type of odor receptor.) Despite this — and still unexplained — a single taste cell seems to respond to certain bitter-tasting molecules in preference to others. The sensation of taste — like all sensations — resides in the brain. Transgenic mice that
- express T2Rs in cells that normally express T1Rs (sweet) respond to bitter substances as though they were sweet;
- express a receptor for a tasteless substance in cells that normally express T2Rs (bitter) are repelled by the tasteless compound.
So it is the activation of hard-wired neurons that determines the sensation of taste, not the molecules nor the receptors themselves.
Umami
Umami is the response to salts of glutamic acid — like monosodium glutamate (MSG) a flavor enhancer used in many processed foods and in many Asian dishes. Processed meats and cheeses (proteins) also contain glutamate. The binding of amino acids, including glutamic acid, takes place on G-protein-coupled receptors that are coupled to heterodimers of protein subunits designated T1R1 and T1R3. Another umami receptor (at least in the rat's tongue) is a modified version of the glutamate receptors found at excitatory synapses in the brain.
http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/T/Taste.html
Perhaps umami isn't just a response to glutamic acid, but also to amines and especially purines.
Labels: MSG
Labels: Failsafe
Labels: Endorphins, Failsafe diary, Moods
Labels: About me, Failsafe diary, Weight
Labels: Failsafe diary
Labels: Epsom Salts, Failsafe diary
Labels: Failsafe diary, Moods
Labels: Failsafe diary, Moods
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Failsafe diary, Moods, Supplements
Labels: Methylation, Weight
Labels: Failsafe diary, Methylation, Supplements
Labels: Failsafe diary, Grains, Methylation, Optimal Diet, Supplements
Labels: About me, Failsafe diary, Weight
Labels: Challenges, Dairy, Failsafe diary
Labels: Failsafe diary, Grains
Labels: Failsafe diary, Supplements
Labels: Failsafe diary, Weight
Labels: Failsafe diary
Labels: Failsafe diary, Methylation, Pfeiffer
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Epsom Salts, Failsafe diary
Labels: Failsafe diary, Optimal Diet
Labels: Amines, Failsafe diary
Labels: Dairy, Failsafe diary
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Failsafe diary
Labels: Failsafe, Portable food, Recipes