Digestion+and+pH



What is Digestion? The food you eat is made mostly of water and three groups of compounds: proteins, carbohydrates, and fats. Other than the water, your body cannot use the foods in the form they are in when they are eaten. Your body must break foods down into simpler substances that can be used for raw materials and energy. This process is called **digestion**. This is when the complex molecules of foods are broken down into smaller molecules. **Digestion** consists of two parts: **mechanical digestion** and **chemical digestion** (Frank, Miller, and Little). These forms of digestions occur in different places in the body. 
 * Mechanical digestion ** refers to the process of chewing. It is a physical process in which large pieces of food are “torn or ground” into smaller pieces (Frank, Miller, and Little 113). In this process, the size of the food decreases, but the substance is not changed, it still has the same chemical properties.

**Chemical digestion** breaks large molecules into smaller molecules. Some of these molecules are used by your body for energy while others become the building blocks for muscle, bone, skin, and other organs in your body. This process takes place with the help of enzymes (Frank, Miller, and Little). An enzyme is a protein that triggers an activity in cells but is unaffected by that activity (Wooldridge). An example of a common enzyme found in the human body is amylase. This enzyme is responsible for breaking down starch into sugar.  Enzymes require specific conditions to work. These conditions include temperature and pH. Some enzymes work well at a low pH, while others work better at a high or neutral pH (Frank, Miller, and Little). Much the same as animals and plants require different conditions to live, enzymes require different conditions within the body to carry out their functions.

pH in the Digestive System As food moves through the body, there are changes in pH that affect the food molecules along the way. The first stop on this journey is your mouth. Your teeth are responsible for mashing the food. Here the food is also mixed with a fluid known as saliva. The scent of food can actually trigger your mouth to produce saliva (Frank, Miller, and Little).

**Resources: **  Frank, David, John Little, and Steve Miller. //Chemical Interactions//. Upper Saddle River, New Jersey: Pearson Education, Inc., 2009. 112-115. Print.

"Man_Chewing." //Family/Health Program//. Web. 13 May 2010. [|www.awrsd.org/oms/family_health_assignments.htm].

Woolridge, Mike. "Your Genes, Your Choices." //Literacy for Health// n. pag. Web. 13 May 2010. .