Can You Smell It? Can You Taste It?

Senses Lab Can you Smell it? Can you Taste it? Introduction: This lab will investigate the anatomy and physiology of taste sensation. Every individual’s perception of taste is different, due to their taste bud arrangement, # of taste buds, the brains perception of which buds are activated, and which region of the sensory cortex receives the stimulus. You will begin by observing the physiology of smell, followed by an investigation into your perception of taste, including the location of your specific taste buds and how your brain perceives/processes the different sensations. It is not as clear as it seems!

Part I A) One by one smell each of the vials. Without saying anything out loud to your partners, write down:  Whether you can smell anything  If you smelled something, did the smells evoke any images, thoughts or feelings? What were they?  If you smelled something, name what it is that you smelled. 1. ______2. ______3. ______4. ______5. ______6. ______

B) Quietly, so that other groups don’t hear your discussions, compare your findings with those of the rest of our group members. Did you find the same things? If you were unable to identify the sources of the smells, explain your difficulty in identifying/labeling the smell?

C) The nose apparently has about 1000 different types of receptors. Each one is sensitive to just one type of odor molecule. Odors like the ones that you smelled often contain many molecules. There are probably more than 1000 different odors, let alone odor molecules in our lives. If the receptors can only register a thousand individual odor molecules, how do you think that your brain is able to distinguish between the thousands of different smells that permeate your world?

D) Take one of the odor vials and sniff it, holding one nostril closed, until you cannot smell the scent anymore [this may take several minutes]. Then open your other nostril. What do you notice? How might you explain what happened?

Your sense of taste is greatly influence by your sense of smell. When your nose is stuffed up like with a cold, you lose up to 80% of your tasting capability.

E) Taste buds respond to different tastes – sweet, sour, salt and bitter (and umami which we will not investigate). Working in pairs, you will determine which part of your tongue is receptive to which tastes. You will need: cotton swabs [4] cup with sugar water cup with salt water cup with lemon juice cup with unsweetened tea cup with plain water

Using a cotton swab – dip it into one of the solutions – and paint your partner’s entire tongue. Take a minute to allow your partner to identify where the taste was more intense. Draw a tongue and use it to identify where each taste was most readily detected. Rinse your mouth with plain water, and repeat with each of the remaining solutions. When you are done, you should have a fairly accurate map of your tongue and its sensitivity to the 4 main tastes.

F) In the front of the class you will find a bowl of Red berries. For now these berries will go unnamed. Place 1 berry in your mouth without chewing it and then wait a few minutes, moving it around your tongue.

G) Repeat part A above (smells). Did your sense of smell get altered as a result of the berry? Explain why it did or didn’t.

H) Then repeat part E above, again creating your tongue taste bud map. What has changed? Have any of the foods changed in taste? Be specific. If so, explain why a change has occurred. Explain the physiology behind this change.

I) This berry, often called miracle fruit or the magic berry is from the Synsepalum dulcificum plant. The pulp of the berry has a glycoprotein in it aptly called Miraculin, made of 191 amino acids and some carbohydrate chains. Come up with some ideas with your group of how this “miraculous” fruit/Miraculin could be used medically or to improve health.

J) There are 2 conflicting hypotheses about the arrangement of taste buds on the tongue. Some scientists claim that different regions of your tongue process different sensations, while others believe every taste bud is capable of processing every sensation. Make an argument for one of the two based on your observations from the lab and readings.

Research abstracts associated with berry…  Read the attached handout on taste intensity.  Understand the concept of ‘Supertaster’

Taste Intensity

Scientists savor a new area of research. Evidence shows that the sense of taste is more complex than previously believed. One set of findings suggests that humans inherit different levels of tasting ability. These levels may influence food preferences and, in turn, health status.

Drano for dinner? Maybe some dishwashing detergent for dessert? For years researchers have known that our brain's ability to recognize tastes with the tongue helps deter us from eating poison. Accumulating evidence now suggests that this taste detection Full size image available system varies in sensitivity between individuals and also may below influence our daily diet. Scientists are finding that people inherit different levels of responsiveness to a particular test chemical. Some can't taste it, while others, dubbed supertasters, compare it to an extremely bitter concoction such as stomach bile. It's gross. It turns out that supertasters tend to find many tastes more intense than other people do.

This research is leading to:

 A clearer understanding of the function of the sense of taste.  Insight on how taste ability relates to picky eating and possibly health status.

Scientists are just beginning to understand the complexity of the sense of taste. It's known that after a few crunches, the spit in your mouth breaks down a wedge of pizza into particles. The molecular crumbs contact the taste buds, which cover the tongue. Studies show that many different interactions take place depending on whether the morsel is of a sweet, sour, salty or bitter origin. In the end, nerve fibers send taste signals to taste centers in the brain. In addition to the basic tastes of sweet, sour, salty and bitter, some researchers say studies show that a meat-like taste, known as umami, exists. Other scientists, however, believe more research is needed to determine if umami is a completely separate basic taste category. A recent finding indicates that specific structures on taste buds detect molecules of glutamate, which produce the umami quality. While many researchers continue to map the molecular underpinnings of taste perception, others are investigating the "broccoli dilemma." Why do some hate it and some love it? Scientists are finding that we inherit a level of tasting ability that appears to influence what we eat. The first indication that taste varied between individuals was found in 1931. A chemist discovered that a particular molecule was undetectable to some and bitter tasting to others. In 1932, researchers found that the reaction to the chemical ran in families.

Since then researchers have found evidence that approximately 25 percent of people are supertasters and find the synthetic compound, propylthiouracil (PROP), intensely bitter. Some 50 percent find it moderately bitter; about 25 percent can't taste it at all. Supertasters may experience an overall higher level of tasting ability than others, according to some evidence. For example, they have a greater number of the structures that often hold the taste buds (see illustration). In addition, supertasters appear to be more responsive to many bitter compounds, including those in coffee, grapefruit juice and green tea. Supertasters perceive saccharin and sucrose as sweeter than other people do. They also seem to be more sensitive to oral pain. The burning heat set off by the chili pepper ingredient, capsaicin, is more intense in supertasters than in others. Scientists plan to investigate how these findings translate into food preferences and influence health. For example, supertasters may face a higher risk of cancer if they find broccoli and other veggies that carry cancer-preventing vitamins too bitter to stomach. On the other hand, a supertaster's discriminating palate may mean a lower risk of becoming overweight, an alcoholic or a smoker. Currently researchers are analyzing the genetic makeup of families in order to locate the gene that is associated with PROP tasting. Researchers have found that, compared to others, supertasters have a greater number of structures that often house taste buds. These pin-head-sized structures, known as fungiform papillae, can be detected by dabbing some blue food coloring on your tongue. The fungiform papillae will remain pink while the rest of the tongue will stain blue. Photos courtesy of Linda Bartoshuk, Ph.D. Yale. Illustration by Lydia Kibiuk. Part II Fungiform papillae density A) Place a drop of blue food coloring on the tip of your tongue, and then swallow a couple of times, or rinse with a swig of water and spit. B) Making your tongue a dry as possible, stick out your tongue and place a paper hole reinforcer on the tip of your tongue in the area shown in the picture. C) The blue dye should stain the epithelium everywhere except on the fungiform papillae. D) Using a flashlight and a magnifying glass (dissecting scope?), count the number of fungiform papillae inside the hole. E) Determine the number of pink papillae that are within the circle and add it to your 1st tongue diagram above.

F) How does this information compare to your partners tongue map? Can you make any correlations?