Taste and Smell
Taste index of sucrose
1
What are two classes of substances that are LIKELY to taste bitter?
1. long chain organics with nitrogen 2. alkaloids (quinine, caffeine, nicotines)
Why is threshold for bitter so low? Why are we so much more sensitive to it?
serves as protective mechanism bc many bitter things are poisons usually causes rejection of the bitter substances
How are smell sensations classified?
seven types 1. camphoraceous (mothballs) 2. musky (perfumes/after shave) 3. floral (roses) 4. pepperminty 5. etheral (dry cleaning) 6. pungent (vinegar) 7. putrid (rotten eggs)
What transmits taste sensation of BITTER to CNS?
since bitter post 1/3 of tongue, glossophayrngeal and vagus nerves
Threshold for bitter by quinine
0.000008 mol/L
Threshold for sour taste by HCl
0.0009 mol/L
Threshold for salty taste by NaCl
0.01 mol/L
Taste index of NaCl and CaCl2
1
What must a substance have so that it can stimulate olfactory system?
1. VOLATILE so it can be breather 2. slightly WATER SOLUBLE so that is can pass thru mucous to olfactor cilia 3. slightly LIPID SOLUBLE bc many constituents of olfactory cilia are lipid
Life span of taste bud?
10 days
How many taste buds do we have?
3000 to 10000
What do umami receptors respond to?
MSG described as delicious
Is sweet taste caused by a single class of chemicals?
No can be stimulated by sugars, alcohols, esters, aa, inorganic salts of lead and beryllium
Ethanol and capsaicin activate what receptor
TRPV1 this is normally activated by hot temp thats why spicy is hot
How many olfactory cells in the olfactory membrane?
about 100 million their cilia penetrate the mucus layer
What causes sour tastes?
acids intensity proportional to log of [H+]
Why is taste important?
allows us to select foods we like to eat and want to eat (healthy)
How many primary senses of color? taste? smell?
color - 3 taste - 5 smell - maybe 50 or more
What is taste threshold?
concentration levels at which they can be detected
Taste and smell combine to create +texture, temp and spiciness of food
flavor
What causes salty tastes?
ionized salts esp by cations like Na+
Even though we have five sensations, why can we identify more than five tastes?
many substances actually stimulate more than one of the receptors creating more taste sensations
What is taste preference?
means that an animal will choose certain types of food in preference to others this helps control the type of diet it eats these change is accordance with needs of body
Methyl mercaptan smell threshold is one 25 trillionth of a gram/mL of air and this is why it is
mixed with natural gas so that we can detect leaks of the odorless gas
What causes bitter taste?
not a single class of chemicals but all are ORGANIC
Principle characteristic of the sense of smell is its threshold
only need minute air concentrations of the odor
Substances that stimulate the bitter taste are almost all
organic compounds
Bitter receptors are located mainly on
posterior third of tongue
What are the five primary sensations of taste?
sour sweet salty bitter umami
Where is olfactory membrane located?
superior part of each nostril surface area of 2.4 sq cm
What is reciprocal of taste threshold?
taste index
Why do you feel like you cant taste anything when you are sick?
the taste sensation is still normal but taste is also composed of a smell odors from food stimulate olfactory system 1000s of times stronger than taste
The sense of taste is a function of what?
various taste buds in the mouth
How many cells are in olfactory epithelium?
~100 million