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Lab 6 1

Lab 6. Energy use

In this week’s lab, you will visualize metabolism in a living organism, evaluate some scientific claims regarding metabolic processes, and use your own scientific and mathematical thinking skills to personally evaluate a “popular” weight loss mantra. Part 1: Sugar Metabolism in Yeast As we are learning this week, living organisms harvest energy from “food” through cellular processes contributing to an organisms “metabolism”. These processes involve the transfer of energy from of carbon based molecules (that were originally produced during photosynthesis) to a more readily useable form (most commonly, ATP), and the carbon is released as waste. This part of the lab will demonstrate the importance of sugar for the metabolic processes of the fungal organism, Saccharomyces cerevisiae, commonly known as baker’s yeast. Yeast are a single-celled type of fungi that humans use and interact with every day. Beneficial applications of these organisms are diverse, ranging from cooking to bioremediation, while some species are also responsible for causing illnesses like athlete’s foot and ringworm. Interestingly (and fortunately for us), yeast can effectively harvest energy from sugar in the absence of oxygen, and this is precisely what we will be observing today. This process is somewhat similar to the aerobic respiration that our (human) cells undergo, in that both processes break down sugar molecules releasing carbon waste; however, no oxygen is required for fermentation. This is why yeast are sometimes called anaerobic organisms. Materials: for this activity, you will need:

 Ruler, able to measure centimeters.

 Marker/tape for labeling

 4 sandwich or quart (or larger) size sealable ziploc bags (if you are able to splurge on bags that you trust will seal, versus the cheaper ones with questionable sealing abilities, do so- it will be worth it).

 4 packages Bakers Yeast (available at any grocery store in the baking aisle)

 Table Sugar (~2 tablespoons or 2 sugar packets; sugar substitute will not work)

 Warm water (4 cups)

 1 tbs measuring spoon for measuring sugar

 1 cup measuring cup for measuring water Experimental Set Up: A. Label your Ziploc bags. Use caution; do not tear or poke a hole in the bag(s)

1: Yeast + Water 2: Yeast + Water 3: Yeast + Water + Sugar

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4: Yeast + Water + Sugar B. Add 1 package of yeast to each ziploc bag. C. Add 1 tablespoon of sugar to yeast in ziploc bags 3 and 4 only. D. Carefully add 1 cup of warm water to each ziploc bag (one at a time is fine).

Eliminate as much air from the bag as possible before sealing and mix carefully.

 Try to dissolve all the solid clumps in the water, but be gentle with the yeast, and try not to damage the bags.

 The less air you have in the bags at this point, the better your results will be. See image:

 Manage your time carefully here, you don’t want too much time to go by between activating (adding the water) the different treatments.

E. Start your timer and check the seal of each bag for good measure (leaks = messy clean up).

F. Measure the height of the Ziploc bag in centimeters (cm). To do this, hold the ruler up

vertically next to the ziploc bag, and record how “tall” the bag is; the distance between the top of the bag and the bottom (surface of the table is fine). Record your measurement in the provided Yeast Metabolism Data table (below). Also note in the table any observations you have about each treatment (color, bubbles, anything else you notice). This is your time 0 measurement.

G. Every 5 minutes for 45 minutes, gently mix solutions inside bags, and repeat measurements.

 Use caution as you approach and pass 45 minutes; the bag may burst (= messy!)

H. After the final, 30-minute, measurement, calculate the change in Ziploc bag height for each treatment by subtracting time 0 (starting) height measurement from the time 30 height measurement (of the same sample). The difference between these values gives you actual increase in height for each treatment. For example, if your time 0 height was 2cm, and your time 30 height was 10 cm, that treatment would have increased by 8 cm. Fill these values in the Change in Height row (labeled H) of the Yeast Metabolism Data table, below.

I. Determine the average change in height for each condition Yeast without or with sugar. To do this, add the values determined for the Change in Height for treatments 1 and 2, and divide this number by 2. This is your average change in height for the minus sugar condition. Repeat this step for the values obtained for treatments 3 and 4 to determine the average plus sugar height change. Fill these values in the Average Height Change row (labeled I) of the Yeast Metabolism Data table, below.

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Note: this experiment can also be performed with balloons attached to the top of ~16oz small spout plastic bottles, as seen in the image (20oz soda or water bottles work well, after they’ve been rinsed thoroughly of course). The visual effect of this set up is much better than with Ziploc bags, but more materials are needed (4 balloons, 4 bottles, funnel for transporting ingredients to bottles, etc….) if you are able to/want to repeat the experiment this way, I highly recommend it (it’s a lot more fun). Show your friends and family your new party trick  Yeast Metabolism Data:

Expired Time

Treatment 1: Yeast+Water

Treatment 2: Yeast+Water

Treatment 3: Yeast+Water+Sugar

Treatment 4: Yeast+Water+Sugar

Height in cm

Observations Height in cm

Observations Height in cm

Observations Height in cm

Observations

0 minutes

5 minutes

10 minutes

15 minutes

20 minutes

25 minutes

30 minutes

35 minutes

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40 minutes

45 minutes

(H) Height Change:

Treatment 1: Yeast+Water

Treatment 2: Yeast+Water

Treatment 3: Yeast+Water+Sugar

Treatment 4: Yeast+Water+Sugar

(I) Avg Height Change

Yeast (minus sugar): Yeast + Sugar:

When you are finished, answer the following questions:

1. Describe your observed results of the yeast metabolism experiment (include observations and average change for each treatment)? Were these the results you were expecting? Is your average an accurate representation of your treatment data? Why/why not? 2. Based on what you learned this week and the conditions that the yeast cells were in during this experiment, which metabolic process did the yeast undergo? What gas was produced? How do you know? Can humans carry out this process, and if so, what purpose does it serve in human cells? 3. If you were to compare the results of this experiment from several different people, assuming that they all implemented the procedure in the exact same way, would you expect each person to get exactly the same results? Why or why not? In your answer discuss possible sources of variation in this experiment. 4. The sugar that was added to the ziploc bags represents the “food” source for the yeast. Where did the energy that the yeast extracted from the sugar originally come from? Explain how you know this. 5. When you make bread, if you just mix flour, sugar and water, the dough does not rise, and the bread will be flat and hard. If you include yeast in the bread dough, then the dough rises and the bread is bigger and fluffier. Use your results from the yeast metabolism experiment to explain how the yeast helps the bread dough to rise.

6. Discuss how this yeast metabolism experiment relates to the material that we learned this week (and previous weeks!). Use specific examples.

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Part 2: Is Lost Weight Really Lost? In the next part of this week’s lab, we will read about some research that used mathematical evidence to answer this very question, but also collected some shocking data about what the general public understands about cellular respiration and human metabolism. Below you will find links to read the original, primary, research article, and a few additional summary articles generated for the popular media based on the original. Original Research Article: http://www.bmj.com/content/bmj/349/bmj.g7257.full.pdf Take some time to review the original article first. Don’t be intimidated. For a scientific article, the language is fairly easy to understand for a non-scientist. That being said, don’t worry if you don’t understand every word. Take notes while you read and try to get the general idea of:

 What is the main point of the study? What was the study trying to find out?

 What are the main conclusions, their results/findings?

 How does the study apply to you, and what we’ve learned this week (and this semester)? After you’ve familiarized yourself with the original article, follow the other links to review the 6 summary articles. As you are reading each, take notes. Consider/evaluate each of the following.

 What is/are the main point/s of the article?

 Are the main points of the article consistent with the original research study? Is the article appropriately using information from the original study, or skewing it/making a new point?

 Do you notice anything questionable about the summary article, for example in terms of disclosures, conflicts of interest, echo chamber, etc…. remember our Lab 1materials!

 Is the source reputable? Remember our Week 1 materials! Summary Article 1: https://www.medicalnewstoday.com/articles/287046.php

Summary Article 2: https://www.scientificamerican.com/article/when-you-lose-weight-wher/

Summary Article 3: https://www.npr.org/sections/health-shots/2014/12/16/371210831/when-

you-burn-off-that-fat-where-does-it-go

Summary Article 4: https://www.sciencedaily.com/releases/2014/12/141216212047.htm

Summary Article 5: http://theconversation.com/when-we-lose-weight-where-does-it-go-91594

Summary Article 6: https://www.beachbodyondemand.com/blog/where-does-fat-go-when-you-

lose-weight

When you are finished, answer the following questions: 7. Compared to the original metabolism research article, which summary article do you find to be the most accurate? Which summary article do you find to be the least accurate? Explain your answer, providing at least 2 valid reasons why for each.

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8. Which metabolism summary article source (publisher) do you find to be the most reputable/trustworthy? Which summary article source (publisher) do you find to be the least reputable/trustworthy? Explain your answer, providing at least 2 valid reasons why for each. 9. Based on the original metabolism research study, when you lose weight, how does the matter leave your body? Identify in what all the forms that the matter is in as well as the percent of each form. With your response, state which article(s) you used to answer and why you chose to use this article as your reference. 10. It is several years in the future, and you are home visiting family for Thanksgiving. During Thanksgiving dinner, your brother is bragging about some of his recent weight loss accomplishments. He says “since he’s shed these 45lbs, that’s 20kg you know, I have all this extra energy”. He takes it even further, saying “as the weight comes off, it transforms right into energy!”. Based on the original research study, explain why this belief may seem logical, but is in fact, wrong. Include in your answer evidence from the original study that illustrates that the majority of people are incorrect in this assumption (hint: look at the figures). 11. It is several years in the future, and you are home visiting family for Thanksgiving. During Thanksgiving dinner, your brother is bragging about some of his recent weight loss accomplishments. He says “since he’s shed these 45lbs, that’s 20kg you know, I have all this extra energy”. He takes it even further, saying “as the weight comes off, it transforms right into energy!”. Based on the original research study, offer your brother a better, scientifically and quantitatively accurate, explanation to his observed phenomenon. Include numerical, quantitative data specific to your brother’s case to support your argument. For this, you must consider how much weight he has lost and based on the article, tell him exactly where that weight went. 12. After completing this week’s course material, you are talking with a friend, who is also taking this class. Your friend mentions that they find it super interesting how a simple, single celled organism, such as yeast can function so similar to us (only in certain ways of course). You ask what they mean, and they say “Well, if you think about it- in the yeast experiment we just did, they “exhaled” the carbon-based product of metabolism, just like we do!” Is your friends statement correct? Why/why not?

Part 3: Is it Really That Simple? It seems obvious, especially after viewing the summary articles in Part 2 of this lab, that we (humans) tend to have a fixation (no pun intended) on diets, fat, and weight. New diets (or lifestyle programs, if we want to use more current terms) seem to come out, one right after another, each claiming to be the next best way to provide quick, permanent, weight loss. However, the researchers behind the original article that we read in Part 2 of this lab argue that weight loss simply represents a balance between intake an output of matter; that to lose weight, you must consume fewer calories than your body uses. The question we will answer in this part of our lab is, is it really that simple? Specifically, as you calculate your own metabolic

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rate and compare it with your typical daily caloric intake, you will put the “eat less, move more” weight loss claim to the test. Before we begin, remember calories are a measurement of energy and because one calorie is a very small unit, food calories are usually measured in units of 1,000 calories, called kilocalories (abbreviated kcal). Also note, although we are limiting our range of study in this exercise to calories only, the skills and information that you will glean here are directly applicable and relevant. To determine your daily energy expenditure/consumption, or metabolic rate, you will incorporate two components: your basal metabolic rate (BMR) and additional calories expended (on top of the cell maintenance/survival processes). Let’s start with your basal metabolic rate (BMR). It is important to note that BMR varies according to the following components (and some others). This experimental procedure takes all these factors into consideration.

 Body style: a tall, thin person has a higher BMR than a short, stout person

 Age: the younger the person, the more likely it is that cell division is occurring; therefore, BMR is higher for younger persons than for older persons

 Sex: males have a higher BMR than females because males have a greater percentage of

muscle tissue
 
 A. To calculate your BMR, use the formula below that is most appropriate for your inherited

(chromosomal based) gender. To do this, you will also need the following information:

 Your weight in pounds (lbs)

 Your height in inches (in)

 Your age in years

Resources: http://www.height- converter.com/

Female: BMR = 655 + (4.354 X weight in lbs) + (4.569 X height in inches) – (4.7 X age in years) Male: BMR = 66 + (6.213 X weight in lbs) + (12.69 X height in inches) – (6.8 X age in years)

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My BMR = _____ kcal. Next, we will use the “activity multiplier” to determine your total caloric expenditure (actual metabolic rate).

To give you an idea how daily activity impacts overall metabolic rate, review the figure. This figure shows the time required to “burn” 4 different caloric values through 3 different activity levels. B. Multiply your BMR (determined in the previous step) by the appropriate activity factor from the list (below) to determine your total caloric expenditure (actual metabolic rate).

 sedentary (desk job, with little or no exercise) = BMR X 1.2

 lightly active (light exercise, 1-3 days/week) = BMR X 1.4

 moderately active (moderate exercise, 3-5 days/week) = BMR X 1.6

 very active (intensive exercise, 6-7 days/week) = BMR X 1.7

My total caloric expenditure (BMR times the selected activity multiplier) = _____ kcal. C. Determine the number of calories for all the food you consume in a single day.

 Select a typical day when you eat your normal number of meals (with fairly average food choices) and record everything that you eat (including amounts and brand names). Consider using the food diary provided below to keep your records.

 Use the following websites to look up food caloric values. You may also find caloric info for specific foods on the food product wrapping or on manufacturers website. Note that preliminary research comparing calorie “calculators” has identified these two within the most accurate (use caution with others). o https://www.webmd.com/diet/healthtool-food-calorie-counter o https://www.myfooddiary.com/?network=g&keyword=food%20calorie%20counter

&matchtype=p&device=c&devicemodel=&adgroup=1037681552&position=1t1&cre ative=273779895484&gclid=Cj0KCQjw45_bBRD_ARIsAJ6wUXREPZgR4ZO9L5ZnsHV H3wK5iNtSeppegjULpzoEDfJVb1QzsGmlhnEaAh3gEALw_wcB

 If you have trouble finding information, use your best estimate. My total caloric intake over the recorded 24-hour period was ______ kcal.

D. Calculate your energy balance as: total kcal consumed – total kcal expended = ____ kcal

E. Return to your actual metabolic rate (energy expenditure calculations), above and

recalculate what your total calorie expenditures would be if you increased your activity

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Lab 6 9

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. My updated caloric expenditure (BMR times the updated activity multiplier) = _____ kcal.

F. Use this updated metabolic rate to recalculate an updated (hypothetical) energy balance, as

updated energy balance = total kcal consumed – updated total kcal expended = ____ kcal Our last step in this part of our lab is too evaluate if our calculations make any (real) sense. G. Click the link; visit the website

https://www.choosemyplate.gov/MyPlatePlan to get your USDA recommended calorie intake values. Click start on the “Get Your MyPlate Plan” widget.

H. When prompted, enter/fill in your

 Age

 Sex

 Pregnant/Breastfeeding Status

 Weight (pounds)

 Height (feed/inches)

 Approximate level of physical activity.

I. Click calculate food plan to review recommended the number of calories that the USDA recommends you intake in order to achieve and maintain a healthy weight. How do these numbers relate to your metabolic rate calculations?

When you are finished, answer the following questions:

13. State and discuss your actual metabolic rate determination and your USDA MyPlate calorie recommendations. Were these consistent? Were they (either or both) what you expected? Why/why not? 14. Visit https://www.choosemyplate.gov/MyPlatePlan and determine how many calories are recommended by the USDA MyPlate program in order to achieve and maintain a healthy weight for a 27-year-old, genetic female, that weighs 145lbs, is 5 feet 7 inches tall. She is not pregnant or breastfeeding, and she is exercises lightly, walking for 30 minutes 1-3 days a week.

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15. Calculate the actual metabolic rate for a 50-year-old, genetic male, that weighs 230 lbs, is 6 feet 3 inches tall. He is very active, running or playing basketball for 45 minutes to an hour 6-7 days a week. 16. Based on this figure, approximately how long would it take to burn 1,000 kcal at rest, by walking, and while jogging? Explain your answer; how did you come to this conclusion? 17. Discuss the meaning and long-term (over time) implications of the energy balance we calculated in the metabolic rate experiment. If a person’s calculated energy balance was positive every day long-term, what effect would that have on body weight over time? If a person’s calculated energy balance was negative every day long-term, what effect would that have on body weight over time? If a person’s calculated energy balance was 0 every day long-term, what effect would that have on body weight over time? Explain your answer (why this would happen) for each situation.

18. How did your calculated energy balance change when you updated (went up or down) an activity level? If your goal was to gain weight, what changes could you make in your daily diet to improve your energy balance situation? If your goal was to lose weight, what changes could you make in your daily diet to improve your energy balance situation? 19. Based on calorie considerations alone, which dieting strategy should be more effective for weight loss: a low carb diet or a low fat diet (recall: Carbohydrates and proteins each contain 4 kcal/g and Fats contain 9 kcal/g)? Explain your answer. 20. Based on your metabolic rate data and calculations, explain why athletes often gain weight when they retire from sports.