Pre-lab Reading
Activity 1: Calories In, Calories Out
There have been several highly publicized diet programs (such as the low-carb diet) that claim to provide significant, permanent weight loss. In most cases, some weight loss occurs, but isn’t sustained over a long period of time. It seems clear that basic changes in the typical American diet (for example, Figure 6.1) are needed to counteract the current “epidemic” of obesity and related health problems. Even young children have been affected.
To lose weight, you must consume fewer calories than your body uses for metabolism and daily ac-tivities. Calories are a measurement of energy. Because one calorie is a very small unit, food calories are usually measured in units of 1,000 calories, called kilocalories (abbreviated kcal). The “magic formula” for weight loss is a simple equation. One pound of fat represents 3,500 calories that the body has stored for later use. To lose a pound of fat, therefore, 3,500 kcal must be expended. The rate of energy consumption by the body is referred to as metabolic rate, which has two components:
• Your metabolic rate consists first of those calories used for basic body maintenance processes such as cell respiration, blood circulation, and removal of wastes. The total number of calories used for basic maintenance is called your basal metabolic rate
• Although basal metabolic rate includes the majority of calories expended each day, it does NOT include calories used for daily activities (walking, studying, shopping, taking notes, etc.). This is the second component of your daily energy consumption
In this activity, you’ll be calculating your approximate energy expenditure for a typical day and comparing it with your typical daily caloric intake.
On-Campus and Online Pre-lab Assignment
Inquiry and Analysis
1. Select a typical day when you eat your normal number of meals. Record everything that you eat (including amounts).
2. Based on the information at the following website, calculate the approximate number of calories consumed for all the food you recorded on your chart. (It might take a little time to sign up for an account at the following website so plan accordingly.) https://www.myfitnesspal.com/
My total caloric intake over the recorded 24-hour period was ________ kcal. (5 points)
Your total caloric expenditure equals the calories expended for basal metabolism (BMR) plus the calories expended for daily activities. You can get a close estimate of the calories expended on daily activities by multiplying your BMR by the appropriate activity factor from the following list.
• •
sedentary (desk job, with little or no exercise) = BMR × 1.2 lightly active (light exercise, 1–3 days/week) = BMR × 1.4
• moderately active (moderate exercise, 3–5 days/week) = BMR × 1.6 • very active (intensive exercise, 6–7 days/week) = BMR × 1.7
My total caloric expenditure (BMR times the selected activity multiplier) = ________ kcal.
3. Calculate your energy balance as follows: total kcal consumed − total kcal expended = ______ kcal.
4. Circle one answer.
My answer to question 3 above was a positive / negative number. Therefore, I consumed fewer / more calories than I expended.
If this day’s diet and activity are typical, over time I will probably lose weight / gain weight / remain the same weight.
5. If you consumed 100 kcal more than you expended each day, how many days would it take you to accumulate 3,500 excess calories (and gain one pound)?
6. Return to your energy expenditure calculations and recalculate what your total calorie expen-ditures would be if you increased your activity multiplier by one level (for example, from light to moderate activity).
If you were already at the highest activity level, recalculate for one level lower. How does the new figure change your energy balance equation?
7. If your goal was to gain weight, what changes could you make in your daily diet to improve your energy balance situation?
8. If your goal was to lose weight, what changes could you make in your daily diet to improve your energy balance situation?
9. Based on calorie considerations alone, which dieting strategy should be more effective for weight loss: a low-carb diet or a low-fat diet? Explain your answer.
Hint: Carbohydrates and proteins contain 4 kcal/g. Fats and oils contain 9 kcal/g
10. Would changing from a low-carb to a low-protein diet have any weight-loss effect? Explain your answer.
11. Based on your calculations, explain why athletes often gain a lot of weight when they retire from sports.
Online Lab 6: Metabolic Rate in Yeast Fungi are eukaryotic organisms that, like animals, are heterotrophs. Fungi must obtain nutrients from the environment in order to obtain the energy they require for survival. Fungi are a diverse and widespread group. There are over 120,000 described species of fungi, and there may be more than a million additional species that are yet uncharacterized! Fungi can live as multicellular organisms (mycorrhizae) or single-celled, free-living yeasts. Some fungi are restricted to life only as multicellular or unicellular organisms, while others can switch between these forms. Sacromyces cerevisceae, or baker’s yeast, is a readily available single-celled fungus that is used frequently in both laboratories and home kitchens. S. cerevisceae consumes sugar to produce ATP, the immediate energy source used by cellular processes. ATP production in these yeast results in excretion of carbon dioxide as a metabolic waste product. Carbon dioxide is a measure of metabolic rate in yeast.
Metabolic rate is sensitive to many factors, including temperature, size of the organism, the type of metabolic pathway utilized for energy formation, and various forms of stress. This experiment will examine the effect of temperature.
Materials • 2 packets active dry yeast (about 4 teaspoons) • Very warm water (105°F–115°F—see instructor’s suggestions) • Cold water • 2 teaspoons sugar, divided • 1 teaspoon baking powder • 5 12-inch balloons (inflate and deflate each balloon 3 times before the experiment).
• 5 narrow-neck empty containers (see instructor’s suggestions—small empty water bottles or empty spice jars work well)
• Camera (cell phone is fine)
Methods 1. Fill out the hypothesis and predictions section of the datasheet before beginning the exercise. 2. Label the containers as follows: positive control (A), yeast + sugar in warm water (B), yeast in warm water (C), yeast + sugar in cold water (D), yeast in cold water (E).
3. For each of container, it may be easier to mix the components together in a separate bowl first and then pour the mixture into the labeled container.
4. Prepare the positive control: measure 1⁄4 cup cold water with 1 teaspoon baking powder and pour into the labeled container A. Swirl gently. Take a prepared balloon and stretch the open end over the opening of the container. Note the time, and set aside.
5. Prepare container B (yeast + sugar in warm water). Measure out 1⁄4 cup warm water into your mixing bowl. Add 1 tsp of sugar and mix. Add 1 tsp active dried yeast and stir to dissolve. Pour the mixture into the container labeled B. You may need to use a rubber scraper to get the yeast into the test container. Stretch the open end of a prepared balloon over the opening of the con-tainer. Note the time, and set aside.
ou may need to use a rubber scraper to get the yeast into the test container. Stretch the open end of a prepared balloon over the opening of the container. Note the time, and set aside.
7. Prepare container D (yeast + sugar in cold water). Measure out 1⁄4 cup cold water into your mix-ing bowl. Add 1 tsp of sugar and mix. Add 1 tsp active dried yeast and stir to dissolve. Pour the mixture into the container labeled D. You may need to use a rubber scraper to get the yeast into the test container. Stretch the open end of a prepared balloon over the opening of the container. Note the time, and set aside.
8. Prepare container E (yeast in cold water). Measure out 1⁄4 cup cold water into your mixing bowl. Add 1 tsp active dried yeast and stir to dissolve. Pour the mixture into the container labeled E. You may need to use a rubber scraper to get the yeast into the test container. Stretch the open end of a prepared balloon over the opening of the container. Note the time, and set aside.
9. Take a photo of your setup and note the time. You will continue your observation for the next several hours, recording the time and taking a photo at each time point. At a minimum, record your observations every 20 minutes for 3 hours (9 time points).
10. Answer the questions in the datasheet.