Calories: Biochemical Energy (page 2)

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Author: Janice VanCleave

Try New Approaches

Is the same amount of energy per minute of time released from all foods? Repeat the experiment replacing the marshmallow with different foods, such as a peanut, cheese, and bread. Science Fair Hint: Construct and display a bar graph indicating the amount of energy released by each food.

Design Your Own Experiment

  1. Use the following steps to calculate the amount of food Calories released by each of the burning foods. See Appendix 2 for a food Calorie sample problem.
    1. Calculate the gram calories released:
    2. gram calories = mass of water × specific heat × temperature change

      Consider the following facts:

      • The specific heat of water is a constant equal to 1 cal/g.°C (calories needed to raise the temperature one gram of water one degree Celsius).
      • The 50 ml of water weighs 50 grams, since the density of water is 1 g/ml.
    3. Convert gram calories to food Calories:
  2. The food used in each experiment is not totally burned. To determine the number of grams of each food sample converted into energy, divide the number of food Calories per gram into the number of food Calories absorbed by the water. A list of food Calories per gram for different foods can be found in a nutrition text.
  3. The human body uses energy through exercise; specific dynamic action, or SDA (digesting and metabolizing food and converting it into energy); and basal metabolism (all the work that goes on inside the body to keep it alive). Energy taken into the body equals energy used plus stored energy. This relationship can be expressed as follows:
  4. energy input = energy output + energy stored

    Energy input is the amount of food Calories eaten. Energy output is the energy expended through exercise, SDA and basal metabolism. The unused energy is stored as body fat SDA is equal to about 10% of your food energy input, and basal metabolism is roughly one food Calorie per hour per kilogram of body weight

    Determine your energy input during a 24-hour period by recording your food intake and using a calorie counter, which can be found in a nutrition text, to determine the food Calories for each food quantity. Record the total food Calories in a data table such as the one shown on the next page. Keep a record of the time duration of each physical activity during the 24-hour period and, with the Calorie counter information found in Appendix 3, calculate and record your exercise calories for the testing period. Calculate your SDA and basal metabolism.

    The total results for one test subject are listed in the data table here. Sample calculations for determining these food Calories, exercise calories, SDA, and basal metabolism are provided in Appendix 4. More information about energy input and output can be found in Carl H. Snyder's The Extraordinary Chemistry of Ordinary Things (New York: Wiley, 1992), pp. 341–344.

    Calories Biochemical Energy

Get the Facts

  1. The number of food Calories in food is determined by a bomb calorimeter. Use a nutrition text to find out how this instrument works.
  2. The first law of thermodynamics states that energy is not created or destroyed. Energy is just changed from one form to another, as it was in the original experiment. In the formation of the chemicals inside the marshmallow, energy was taken in and stored. The burning of the marshmallow released this stored energy. Chemical reactions are usually accompanied by the absorption or release of energy. Find out more about the gain and loss of energy during chemical changes. Define and provide examples of endothermic and exothermic reactions.
  3. Fats yield more than twice as much energy per gram as do proteins or carbohydrates. Find out more about the energy differences of these major food components. What is the actual quantity of energy provided by each? What is adipose tissue and how much energy can it store?
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