1. Smell arises from nerve signals originating in nasal epithelia. Molecular components of this process include 7TM proteins that bind odorants, which activates a G protein called Golf . Golf, in turn, binds GTP, activates adenylate cyclase, stimulating cAMP synthesis. cAMP binds to a cAMP-gates ion channel in the cell membrane allowing cations to enter the cell, starting the nerve signaling process.
2. Humans have only about 30% of their odorant rcceptors active, whereas rodents a large percentage of their 1000 receptors active. Olfactory receptors (ORs) are similar in slightly structure to the beta-adrenergic receptor involved in epinephrine signaling. Each olfactory neuron synthesizes only a single OR. This differs from individual taste buds, which each synthesize several receptors for tastes.
3. We are able to perceive a VERY wide range of smells, due to the combinatorial mixing of signals from the many different 7TMs at the end of olfactory cells.
4. OR signaling proceeds via 7TM receptors that synthesize cAMP when an odorant binds to the 7TM (through the usual mechanisms). cAMP binds to a channel protein that opens when cAMP binds to it, allowing Ca++ and Na+ into the cell, thus starting the signal.
5. Smell neurons terminate in very different regions of the brain.
6. Taste sensing is related to smell. Not all tastes have odors, however. In contrast to smell, we only have 5 primary tastes we detect through taste buds located on distinct areas of the tongue. The five primary tastes are sweet, sour, bitter, salty, and umami.
This course in general biochemistry is intended to integrate information about metabolic pathways with respiration (respiratory control) and initiate the student into a microscopic world where blueprints are made of deoxyribonucleic acids, factories operate using enzymes, and the exchange rate is in ATPs rather than Yens or Euros. Beyond explaining terms, and iterating reactions and metabolic pathways, this course strives to establish that the same principles that govern the behavior of the world around us also govern the transactions inside this microscopic world of the living cell. And by studying and applying these principles, we begin to understand cellular and bodily processes that include sensory mechanisms.
1. Lipids, Membranes and Transport
2. Electron Transport, Oxidative Phosphorylation and Mitochondrial 3. Transport Systems
3. Lipid Metabolism
4. Nucleotide Metabolism
5. DNA Replication