bio265l_document_W11 Worksheet Metabolism Lab -1

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Brigham Young University, Idaho *

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Biology

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Apr 26, 2024

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W11 Worksheet: Metabolism Lab Follow the instructions below very carefully. Many of the items in this assignment require reading, or videos, or something else to do. Each question has either a text box that can be filled out or a box that can be checked to show completion. Be sure to type out your answers completely and expand the text boxes if you need the additional space. Question 1 --- 2 points Basic Metabolic Rate Body metabolism simply means all of the chemical reactions taking place in the cells of the body and the metabolic rate is normally expressed in terms of the rate of heat liberation during those chemical reactions. Metabolic rate is expressed as kilocalories (Cal) per hour. Since direct measurement of heat production from the whole body involves very cumbersome and expensive apparatus, this method has been reserved to check the validity of indirect methods. Indirect methods use measurement of oxygen consumption as an indicator of heat production. The amount of heat produced when one liter of oxygen is metabolized depends on what type of nutrient is being utilized. When one liter of oxygen is metabolized with glucose, 5.01 Cal of energy are released; when metabolized with starches, 5.06 Cal are released; when metabolized with fat, 4.7 Cal, and when metabolized with protein 4.6 Cal. It has been determined that for the average diet, approximately 4.825 Cal are released per liter of oxygen consumed. Using this value, we can compute a relatively accurate estimate of the metabolic rate. Metabolic rate is affected by any factor that increases chemical activity in the cells. Listed below are some of the factors that are known to have an effect on metabolic rate. 1. Exercise: Exercise causes by far the most dramatic changes in metabolic rate. In this lab procedure we will determine the effects of exercise on metabolic rate. 2. Age: The metabolic rate of a newborn child in relation to his body surface area is almost twice that of an aged person. Metabolic rate drops rapidly for about the first 20 years of life and then continues to slowly decline for the rest of a person’s life. The high metabolic rate in children results from both high rates of cellular reactions as well as from rapid synthesis of cellular materials and growth of the body. 3. Thyroid Hormones: These hormones control the rate of activity of almost all the chemical reactions in the body. Hypo and hyper secretion of thyroid hormones have major effects on metabolic rate. 4. Sympathetic stimulation: Stimulation of the sympathetic nervous system increases the metabolic rates of essentially all of the tissues of the body. 5. Growth Hormone: GH can increase metabolic rate as much as 15 to 20 percent as a result of direct stimulation of cellular metabolism. 6. Fever: Chemical reactions in the body increase when body temperature increases. 7. Climate: Studies of metabolic rates of persons living in different geographic regions have

shown as much as 10 to 20 percent lower metabolic rates in tropical regions than in arctic regions. This is probably due to adaption of the thyroid gland with increased secretion in cold climates and decreased secretion in hot climates. 8. Male Sex Hormones: Males generally have a metabolic rate that is about 10 percent greater than females due to the effect of the male sex hormones. 9. Malnutrition: Prolonged malnutrition can decrease metabolic rate by as much as 20–30 percent. This decrease is thought to be caused by the lack of necessary nutrients in the cells. However, recent studies indicate that metabolism tends to slow down even during strict diets suggesting that the body is attempting to preserve calories Do you think your metabolism has increased, slowed down, or stayed the same since you began to attend college? Explain. Your answer: I personally think that my metabolism has increased since beginning college. I’ve been more aware of what I put into my body and more into self-care. I’ve had to walk everywhere and have increased my exercise. Question 2 --- 2 points Which of the following would be most likely to decrease a person’s metabolic rate? Choose one: ☐ A fever ☐ Hyperthyroidism ☐ Pituitary dwarfism ☒ Puberty Question 3 --- 2 points VO2 Max VO2 max is the maximal amount of oxygen that a human body can use. VO2 max is often a favorite measurement to assess someone’s fitness level. VO2 max is a good measurement of fitness for the following reasons. 1. Muscle cells have the ability to use more oxygen than any other body cell. So, if a person has more muscle tissue, then they would have the possibility to use more oxygen than

someone with less muscle tissue. The number and health of your muscle cells determines strength and endurance which is a characteristic of fitness. 2. An exercising muscle cell is capable of using nearly all of the oxygen delivered to it and could probably use even more if it was possible to deliver more. Our cardiovascular system is responsible for delivering oxygen. If we have a large and strong heart (like Lance Armstrong did) and if we have healthy blood and healthy blood vessels, then we should be able to deliver more oxygen, which will be used by our muscle cells during exercise. Fitness is characterized by many things, including a strong and healthy cardiovascular system. In short, a person with lots of healthy muscle tissue and a strong cardiovascular system would be able to use more oxygen. If we measure the maximal amount of oxygen that a person can use, then we get an idea of their peak fitness level. VO2 max is usually measured as mL of oxygen, per kg of body weight, per minute (mL/kg/min). Measuring it this way allows us to compare VO2 max across different individuals and compare “apples to apples.” For example, a large, obese man might use a lot more oxygen than a small petite woman (because he has a lot more body cells). But, if we compare what one kg of the obese man's body mass does compared to 1 kg of the woman's body mass, then we see true differences. One kg of the woman’s body mass is simply going to burn more oxygen per minute than one kg of the man's body mass because she has a greater density of muscle in that kg, and she has a greater ability to deliver oxygen to that kg of body mass. Measuring VO2 max can be pretty involved. It involves collecting all the gas that a person breathes in and out. We find that a person breathes in a certain amount of oxygen in a single inspiration, and they breath out a little less oxygen in a single exhalation. The difference is what their body used. If we measure the amount of oxygen that a person breathes in and out while they exercise as hard as they possibly can, then we can see their VO2 max. Of course, it is difficult to directly measure a VO2 max, and takes a lot of specialized equipment. However, there are many ways to estimate it. The website, “ shapesense ” (links to an external site) has some ways to estimate VO2 max. Choose one of the ways, and write your estimated VO2 max in the box below (Keep in mind that generally, the more physically hard it is to do the test, the more accurate it is … this is why the 1.5 mile run is the most accurate test on the web page). Go to the VO2 and VO2 Max page (links to an external site) if you would like to see a page that organizes your VO2 max in fitness categories. Your answer:

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