Lab 3 Digestion, Absorption, and Transport

Taste Sensitivity(For Question 1)

The mouth is the first organ in the digestive tract, and as food is chewed into smaller pieces and dissolved in digestion fluids and beverages, taste bud on our tongues are stimulated. When stimulated, the taste buds detect one (or a combination) of the four basic taste sensations: sweet, sour, bitter, and salty. Some scientists also include the flavor associated with monosodium glutamate, which is sometimes called savory – or its Asian name, umami (oo-MOM-ee). In addition to these chemical triggers, aroma, texture, and temperature also affect a food’s flavor.

Taste buds all over the tongue have nerves that sense all flavor sensations. The simple tongue taste map that you may have been taught early in life – the idea that salty/sweet taste buds are located near the front of your tongue; the sour taste buds line the sides of your tongue; and the bitter taste buds are found at the very back of your tongue – has been oversimplified. The tongue can detect all tastes nearly equally.

Studies on the relationship of taste and smell to eating behavior and personality explore how people differ in their food choices based on their perceived tastes, smell and flavor of food. Food preferences and eating habits differ greatly among people, as some perceive food flavors more intensely than others do. As a result, they may reject foods that taste overly bitter like some vegetables, or prefer foods that are sweet or flavored with fat causing an imbalance in diet ad increasing risk for chronic diseases.

What type of a taster are you? Do you like the taste of sweet and sour? There is evidence that these tasters are accepting to the consumption of fruit. Are you sensitive to bitter flavors? If so, you may not enjoy the taste of vegetables. Tasters are broken down into three categories:

Supertasters – Those who preserve taste more intensely and are especially sensitive to bitter tastes.

Tasters – Those who think about all foods positively.

Non-tasters – Those who prefer intensely sweet food the most.

What are some other differences between non-tasters and supertasters? The tongue’s anatomy depicts clusters of pain fibers associated with each taste bud. A supertaster has a higher-than-average number of taste buds. Supertasters are also super-perceivers of oral pain, such as the burning sensation of capsaicin and ethanol. This anatomical structure of supertasters also affects the perception of fat.

Taste buds are imbedded in tongue tissue within fungiform papillae – mushroom-like structures equipped with touch fibers. Fatty food enters the mouth, pushing touch fibers that trigger touch responses. Because supertasters can sense more touch than the rest of the population, fat produces a greater amount of sensation in supertasters. This provides supertasters with a mixed bag of sorts. On one hand, they avoid fatty and sweet foods, making them thinner with a lower risk of cardiovascular disease.

Supertasters also have a lower occurrence of alcohol and smoking addictions, as those flavors are unpleasant. On the other hand, they tend to eat less fruit and vegetables, making them more susceptible to certain cancers.

Digestion and Absorption of Nutrients(question 2)

During the digestive process, both physical and chemical means are used to break food into its smallest components for absorption. Carbohydrates are digested to single sugar units called monosaccharides. Proteins are broken down to single amino acids and fats are digested to fatty acids, monoglycerides and glycerol. You’ll learn more about these molecules in later chapters.

To accomplish this complete breakdown of macronutrients, the digestive system includes organs in the digestive tract as well as accessory organs outside of the digestive tract that produce and/or contribute digestive fluids. Actions of specific muscles churn and grind food into smaller chunks and pieces, and others push digesting food through to expose them to the different digestive fluids in each part of the GI tract. Once food is digested into the smallest units of individual nutrients, they can be absorbed into blood or lymph.

Some nutrients can pass freely into intestinal cells and then into blood or lymph. Others needs some help from special transport proteins to get from one side of the cell membrane to another. Some nutrients require not only a special transport protein, but also energy for absorption. You’ll learn more about the nutrients absorbed by simple diffusion, facilitated and active transport and in what part of the GI tract absorption of each nutrient occurs in Chapter 3 of your textbook.

In this lab, we’ll trace the journey a common food takes through the digestive tract, documenting what happens at each stage and how the different components of the food are absorbed.

Common Digestive Problems (For Question 5)

The facts of anatomy and physiology presented in this lab permit easy understanding of some common problems that occasionally arise in the digestive tract. We don’t usually give any thought to what happens to the foods we eat unless something goes wrong with the digestive and/or absorption processes. But when there is a problem, it can make us miserable.

Some digestive problems, such as vomiting or diarrhea, are the result of eating contaminated food and resolve on their own. Others can be caused by weight gain, such as gastrointestinal reflux disease (GERD), and yet others have their origin in genetics like Celiac disease. Highlight 3 reviews some common digestive problems and strategies to overcome them.