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Related Concept Videos

Olfaction01:25

Olfaction

The sense of smell is achieved through the activities of the olfactory system. It starts when an airborne odorant enters the nasal cavity and reaches olfactory epithelium (OE). The OE is protected by a thin layer of mucus, which also serves the purpose of dissolving more complex compounds into simpler chemical odorants. The size of the OE and the density of sensory neurons varies among species; in humans, the OE is only about 9-10 cm2.
The olfactory receptors are embedded in the cilia of the...
¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons01:03

¹H NMR Chemical Shift Equivalence: Homotopic and Heterotopic Protons

Protons in identical electronic environments within a molecule are chemically equivalent and have the same chemical shift. The replacement test is a useful tool to identify chemical equivalence and predict NMR spectra. A substituent replaces each of the protons being examined and the resulting molecules are compared. If the same molecule is obtained, the protons are equivalent or homotopic. Replacement of any hydrogens in ethane by chlorine yields chloroethane because all six protons are...
¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons00:58

¹H NMR Chemical Shift Equivalence: Enantiotopic and Diastereotopic Protons

Replacing each alpha-hydrogen in chloroethane by bromine (or a different functional group) yields a pair of enantiomers. Such protons are called prochiral or enantiotopic and are related by a mirror plane. Enantiotopic protons are chemically equivalent in an achiral environment. Because most proton NMR spectra are recorded using achiral solvents, enantiotopic hydrogens yield a single signal.
In chiral compounds such as 2-butanol, replacing the methylene hydrogens at C3 produces a pair of...
Physiology of Smell and Olfactory Pathway01:20

Physiology of Smell and Olfactory Pathway

Humans detect odors with the help of specialized cells located in the upper part of the nasal cavity, called olfactory receptor neurons (ORNs). ORNs possess hair-like structures called cilia, which are receptive to sensations from the inhaled air. When an odorant molecule binds to a specific receptor on the cell of the cilia, it leads to a series of events that ultimately cause the ORN to send electrical signals to the olfactory bulb in the brain through the olfactory nerves.
The olfactory...
Inductive Effects on Chemical Shift: Overview01:27

Inductive Effects on Chemical Shift: Overview

The protons in unsubstituted alkanes are strongly shielded with chemical shifts below 1.8 ppm. Methine, methylene, and methyl protons appear at approximately 1.7, 1.2 and 0.7 ppm, while the proton signal from methane appears at 0.23 ppm. An electronegative substituent, such as chlorine, withdraws the electron density from the protons, increasing their chemical shift. Progressive substitution of the hydrogens in methane by chlorine shifts the proton signals increasingly downfield, to 3.05 ppm in...
Olfactory Receptors: Location and Structure01:03

Olfactory Receptors: Location and Structure

The process of olfaction, also known as the sense of smell, is a sophisticated chemical response system. The specialized sensory neurons that facilitate this process, known as olfactory receptor neurons, are situated in an upper segment of the nasal cavity, known as the olfactory epithelium. Olfactory sensory neurons are bipolar, with their dendrites extending from the epithelium's apex into the mucus that lines the nasal cavity. Airborne molecules, when inhaled, traverse the olfactory...

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Related Experiment Video

Updated: Jun 28, 2026

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase
09:53

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase

Published on: April 23, 2019

Odor concentration invariance by chemical ratio coding.

Naoshige Uchida1, Zachary F Mainen

  • 1Cold Spring Harbor Laboratory, Cold Spring Harbor NY, USA.

Frontiers in Systems Neuroscience
|October 30, 2008
PubMed
Summary
This summary is machine-generated.

Rats can identify chemical mixtures by component ratios, not just concentration. This suggests a general mammalian olfactory system strategy for recognizing odors regardless of dilution.

Keywords:
concentration-invarianceodor recognitionolfactionratio

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Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility
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Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility

Published on: July 27, 2017

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Last Updated: Jun 28, 2026

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase
09:53

Real-time In Vitro Monitoring of Odorant Receptor Activation by an Odorant in the Vapor Phase

Published on: April 23, 2019

Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility
07:49

Electrophysiological Recording from Drosophila Trichoid Sensilla in Response to Odorants of Low Volatility

Published on: July 27, 2017

Area of Science:

  • Neuroscience
  • Olfactory system
  • Chemical signaling

Background:

  • Animals use chemical signals for environmental information.
  • Olfactory receptor neuron activation varies with chemical concentration.
  • Recognizing stimuli across different concentrations is a key olfactory challenge.

Purpose of the Study:

  • To investigate if rats, like insects, use chemical ratios for odor recognition.
  • To determine if rats can generalize odor perception across concentration changes.

Main Methods:

  • Psychophysical methods were employed.
  • Rats were tested on their ability to classify binary odor mixtures.
  • Generalization over a tenfold concentration range was assessed.

Main Results:

  • Rats classify binary odor mixtures based on the molar ratios of their components.
  • This classification is spontaneous and generalizes across significant concentration variations.
  • The findings extend beyond insect pheromone signaling.

Conclusions:

  • Extracting chemical ratio information is a general solution for concentration-invariant odor recognition in mammals.
  • This mechanism is not limited to pheromone-based communication.
  • Mammalian olfaction likely employs ratio-based coding for stable odor identification.