A LOOK AT DIGESTION – MAKING MOLECULES AVAILABLE FOR METABOLISM Lab: Creating an Artificial Stomach and Duodenum

Digestive Tract Single two-ended tube with specialized parts that process food in a fixed order Moves nutrients, water, and electrolytes from external to internal environment Associated organs: liver, gall bladder, pancreas

Ingested materials Simple and complex carbohydrates Proteins Fats

Enzymes and Bile salts Break down food into amino acids, simple sugars and fatty acids Decomposition of macromolecules by enzymes is principal means of chemical digestion Bile (from liver) coats fats & mechanically reduces them to globules and droplets  Nutrients actively or passively absorbed through intestinal epithelium  Nutrients transported via circulatory system into cells  Nutrients used for cellular metabolism or stored for later use

Your investigation Can you figure out what kind of digestion occurs in the stomach and duodenum by modeling digestion of various foods?

Materials You will be investigating the enzyme pepsin under different conditions of pH. Contents of bag pHPepsin (mL) HCl (mL)NaHCO3 (g) pepsin HCl Artificial stomach Artificial duodenum

What to do: Label 4 zippered bags according to the chart on the previous slide. (Don’t forget your name(s)) Line four 250-mL beakers with one each of the bags. Fill each with the correct solutions. Do not add NaHCO3 yet. Cut up the food samples into uniform sizes. (~1cm) Place a set of the foods into each bag and seal. Place sealed bags in beaker an then the 37°C water bath. Place NaHCO3 in the bag right before you seal it and place it in the water bath.

Record results Questions: 1. Which foods were digested? 2. Which samples are controls and why? 3. What conditions maximize digestion? 4. Why is buffering gastric juices so important?

Report Title, Objective or purpose, Summary of procedure, Data (Table?), Results, Conclusion, Questions.