The objective of this science fair project is to measure the concentration of glucose in a variety of common fruits and juices.
Fresh pineapple, chilled watermelon, and an icy cold soft drink on a hot summer's day. What do these things have in common? They all taste so good because of the sweetness the sugar inthem provides. When you think of sugar, you probably picture the white granules you put in cookies, that your parents put in their coffee, or that you put on your cereal. Actually, this is just one kind of sugar, called sucrose, which is extracted from sugar cane or sugar beets. Technically, sugar is a carbohydrate that occurs naturally in every fruit and vegetable. It is the major product ofphotosynthesis, the process by which plants transform the Sun's energy into food.
Glucose is another type of sugar and is a very important biochemical. For one thing, glucose is the only fuel used by brain cells. Glucose is also an important source of energy for muscles and other tissues in the body.
The glucose in your blood comes from the food you eat. Complex carbohydrates, found in pasta orcereal, for example, are long chains of sugar molecules that are broken down by enzymes to simple sugars, such as glucose. Sucrose, or table sugar, is also broken down to form glucose. Because carbohydrates and sucrose in food are broken down to form glucose, the level of glucose in your blood goes up after you eat.
Like most of the chemicals in your blood, the level of glucose must be tightlycontrolled. The level of glucose in your blood is controlled by insulin, a hormone made in the pancreas. Too little glucose, and your brain and other organs will not have the energy they need to function. Too much glucose in the blood can cause diabetes, which is a serious and growing health problem in the United States.
In this science fair project, you will investigate the concentration of glucosein common fruits and juices. In order to measure the glucose concentration, you will use glucose strips. These strips were developed to help people with diabetes maintain a healthy level of blood glucose. When you dip the test strip into a liquid, such as orange juice, it changes color if glucose is present. The degree of color change depends on the concentration of glucose.
Terms, Concepts andQuestions to Start Background Research
* Complex carbohydrate
* Negative control
* Positive control
* Dilution series
* Put these five food sugars in order, from the sweetest to the least sweet: glucose, fructose,sucrose, lactose, and maltose.
* What is the concentration range of glucose in healthy people? What is the level in diabetics?
* Which foods have a naturally high level of glucose?
* Which fast foods have the highest glucose levels? (Hint: Look at the nutrition data on the restaurants' websites.)
* Why do certain foods have high natural sugars? (Hint: Fruits contain seeds, and theplant's chances of spreading are better if the seeds are dispersed).
* How many calories are in 1 gram (g) of glucose?
* How does the glucose test strip work?
* HowStuffWorks.com. (2008). How Food Works. Retrieved September 11, 2008, from http://recipes.howstuffworks.com/food2.htm
* Nutrition Data. (2008). Foods highest in Glucose. Retrieved September 11, 2008, fromhttp://www.nutritiondata.com/foods-000010000000000000000-1.html
Materials and Equipment
* Glucose test strips; available at most drug stores. The Experimental Procedure is based on Bayer's Diastix reagent test strips for glucose determination in urine. Urinalysis is serious stuff, and is important in medical diagnostics. For the purposes of this experiment, you will use the glucose strips...