78

There are about 100 (Purves, 2001) to 400 (Zozulya et al., 2001) functional olfactory receptors in man. While the total tally of olfactory receptor genes exceeds 1000, more than half of them are inactive pseudogenes. The combined activity of the expressed functional receptors accounts for the number of distinct odors that can be discriminated by the human ...


11

Two compounds are specifically associated with the smell of decaying cadavers (Hoffman et al., 2009), namely: 1,5-pentanediamine (cadaverine), and 1,4-butanediamine (putrescine) Cadaverine is produced by breakdown of lysin and putrescine by the breakdown of ornithine (Science ME). Both are nitrogen-rich compounds and particularly pungent-smelling. ...


10

cis-3-hexenal is probably the main reason. It is one of the main chemicals in fresh-cut grass smell (lots of references besides wiki if you google it). This fairly comprehensive paper on watermelon odorants also says that they find a lot of cis-3-hexenal in fresh cut watermelon. See tables 3.1, 3.2 and 3.3.


9

There are many, many more parameters than 200! As an example, look at the nomenclature system for olfactory receptors (ORnXm). "OR" is the root name (Olfactory Receptor superfamily) n = an integer representing a family (e.g., 1-56) whose members have greater than 40% sequence identity, X = a single letter (A, B, C, ...) denoting a subfamily (>60% sequence ...


7

Nice question! It would, obviously, be a long answer if I talk about all types of sulfur compounds here. So I will take up just 2 examples to explain this. Thiols: when we talk about sulfur compounds with foul smell, thiols (mostly) come to the top in the list. Thiols (R-SH) are a class of compounds famous for their smell. Some examples of thiols include: ...


6

The dog's ability to smell the world around him and to interpret these odors depends on a complicated chemical sensory system. First of all, it possesses mobile nostrils, that help to determine the direction of the smell. Then comes sniffing, the ability to disrupt the air with a regular pattern of breathing that, through laboratory testing, is structured in ...


5

According to CDC.gov and Toxnet, bitter almonds contain cyanide, which, gives them the characteristic odor, but this can be also due to benzaldehyde (PubChem), which is, by the way, used as almond flavor for cooking (Wikipedia). Garlic has its odor due to allyl methyl sulfide (Wikipedia) and not due to arsenic, which is not present in garlic in significant ...


5

With regards to the similar chemicals having similar smells, it does seem that there are trends with smell association and functional group. This wiki article has a good list of compounds and their smells, and some classes definitely give similar types of smells, amines are rotting/fecal smells (hence the names putrescine and cadaverine), while esters are ...


4

Senses in general adapt to continuous stimulation due to various processes. One such process is simply the exhaustion of the reserves of a receptor, or secondary neuron, due to a depletion of neurotransmitters. Entering a room activates a fresh pool of chemical receptors, thereby generating a clear sense of smell. However, this dims due to adaptation. ...


4

Short answer One way to distinguish between the olfactory and gustatory system in fish is by their anatomical differences. For example, olfactory receptors are clustered in the nasal region, while gustatory receptors are scattered in the head region and beyond. In turn, olfactory information is sent via a single cranial nerve to the brain, while the ...


3

Yes, it certainly is. But I cannot guarantee that all have been properly determined. For that, we would have to find the basic unique values (like the Red, Green and Blue in the case of colors). Currently, we have 10 unique human detectable smells: The wood-like smell, the floral/fragrant one, non-citrus, chemical, sharp(garlic-like), sweet, menthol, ...


2

Animals smell in stereo. Just the way you need 2 ears to know the direction of sound, you need 2 nostrils to know the direction of odor source. Sniffing around helps in doing exactly that as you sample from different locations; there is inter-nostril concentration difference and inter-nostril timing difference of when the molecules hit the olfactory membrane....


2

One olfactory acuity rating method that has found acceptance in some studies (despite the commercial-sounding name) is based on "Sniffin' Sticks," "a test of nasal chemosensory performance that is based on penlike odor-dispensing devices. It is comprised of three tests of olfactory function: tests for odor threshold, discrimination and identification. ...


2

I could not find a concrete definition after searching several sources, but after reading a few papers I think the term Pure Odorant refers to its Olfactory Bulb profile. Peanut Butter will stimulate specific Olfactory nerves, and only that set of nerves, whereas impure Odorants may stimulate part of the profile and also other parts of the Bulb depending ...


2

Yes, changing the scent has been accepted by most snake breeders as a method to feed stubborn snakes (reference). For example, if your snake prefers chicken, and wont accept mice, rub a chick on a pre-killed mouse and this may trick it into eating the mouse (reference). With regard to garter snakes, the diet may change based on its habitat, its age and even ...


2

As nobody is suggesting an answer I'll give my guess that I already discussed in the comments and give some extra details about ongoing debates on the subject. We'll start with the sense of color sight in order to make easier. One can argue that we see in 3 dimensions because we use three cells which level of activation inform the brain of the color. I ...


2

Here is the paper which directly answers your question. Urban NN. Lateral inhibition in the olfactory bulb and in olfaction. Physiology & behavior. 2002 Dec 31;77(4):607-12. A few salient points: It is true that the spatial gradient of sensory attributes is not as clear in the olfactory bulb-neuronal topography as it is at other places with lateral ...


2

Olfaction is the result of the neuronal impulse of ligand / receptor binding. To smell something requires 1) Specificity between the receptor and the ligand, 2) Concentration of the ligand molecule, and 3)The receptors that are on the surface of neurons in the olfactory bulb. As for metabolize, then you need to be much more specific in defining what you are ...


2

Smell samples the chemical composition of the environment, the groups of molecules you are sampling in those examples still exist in nature. It is like asking why being able to taste pizza would evolve, it doesn't, not by itself anyway, it is the inevitable result of being able to taste the things and conditions that make up pizza, carbohydrates, proteins, ...


2

The vast majority of the things you smell are odorants, or volatile molecules; not spores. They are light compounds that have high vapor pressure (are airborne), and that interact with your chemoreceptors in your nose (can be smelled). The most-often reported microbial volatile organic compounds in living environments according to this study are as follows: ...


2

The idea that males and females react differentially to various smells in the context of “hard science” alludes to the concept of sexual dimorphism in olfactory signaling, which has been investigated: Stowers & Logan. Sexual dimorphism in olfactory signaling. Current Opinion in Neurobiology. 2010. 20,770-775. What makes males and females ...


1

Short answer Third-order olfactory neurons project to the thalamus and mediate conscious perception of odors. Background The human olfactory system is schematically depicted in Fig. 1. The olfactory system is indeed interesting, as it is the only sensory system in which the primary receptor cells project directly to the brain. The olfactory cells in the ...


1

The problem with odors is that no known odorant hits only one olfactory receptor. A saturating concentration of compound X for receptor A might be saturating another receptor B, but not receptor C. If you now decrease the concentration, receptor A is still saturated, receptor B is only partially activated and receptor C is not activated at all. Since smell ...


1

In addition to olfactory and gustatory, fishes have two more chemoreceptor systems, solitary chemoreceptor cells and free nerve endings (Finger TE 1997). Asking why do they have all these chemorecepor systems is 'little bit' difficult in the light of evolution. But we can definitely look at this question by using some comparative studies. Hence, this answer ...


1

Chloride (Cl2) carries 34 protons and electrons. A common example of a relatively heavy odorless gas is CO2, carrying 22 protons and electrons. All noble gases are odorless. The heaviest, naturally occurring noble gas is Radon, which has a proton count of 86. Ununoctium, an exotic artificial element with atomic number 118, is a noble gas too. However, ...


1

Originally I wanted to try this experiment during sleep, however, the K&R "Principles and practice of sleep medicine" 4th edition, on page 16, under "Olfactory system" mentions that both pleasant (peppermint) and unpleasant (pyridine) smells were poorly recognized during sleep: Both well recognized during stage 1 sleep Peppermint not consciously smelled ...


1

Scents can make memory recalls. We experience this very often, like when we repeatedly smell a good perfume in ,say a shopping mall , and when some person uses it too, we recall the memory of the shopping mall. This hqppens especially when the smell is associated with a very good or very bad incident. For an experiment, you can expose yourself or someone to ...


1

To answer this question, you need some background info first. There are three "systems" used for the sense of smell. The first is the olfactory system. This system allows us to recognize what a smell is. You can tell the difference between gardenias and grass because of your olfactory system. The second system is the trigeminal system. This system tells you ...


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