CHAPTER 6 Test Your Knowledge
Driving Question 1
Why do humans weigh more now than in the past?
By answering the questions below and studying Infographics 6.1, 6.2, and 6.3, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
A 5'6? female weighs 167 pounds. Use Infographic 6.2 to determine her BMI. Would she be considered underweight, normal weight, overweight, or obese?
Her BMI would be ~27, which would place her in the overweight category according to the CDC.
If a person wants to lose weight, which of the following are viable strategies?
a. substituting plain water for regular soda
b. eating the same number of Calories, but eating them all as fruit and veggies instead of burgers and fries
c. adding more fruits and veggies on top of the current diet
d. exercising more
e. a and d
e
USE IT
If you frequently crave French fries, how could you modify your lifestyle to eat fries without gaining weight? Explain your answer.
In order to keep eating fries without gaining weight, you would have either to consume Calories from other foods, or exercise more (to burn any extra Calories from the French fries). You could also combine dietary modifications and exercise to maintain your current weight.
Why do you think that longer meal times translate into fewer Calories consumed?
There are many possibilities. One is that by spending longer eating each meal (eating more slowly), there is time for the body to register that it is “full”—that it has had enough—before an excessive amount of Calories have been wolfed down.
If the government were to issue tax incentives to reduce obesity in the United States, which of the following do you think would be most effective? Explain your choice.
a. taxing foods high in fat
b. giving tax breaks to people who join gyms or health clubs
c. giving rebates for purchasing fresh fruits and vegetables
d. paying enhanced salaries for teachers in elementary and middle schools to provide education about diet and nutrition
Answers will vary. Possible justifications for each choice are given here. a: Taxing foods high in fat might discourage people from buying these (more expensive) foods and encourage them to purchase foods that may be lower in Calories (because they will be lower in energy-dense fats and higher in carbohydrates and proteins). b: Giving tax rebates for joining a gym or health club is an incentive that may help offset the cost of joining the gym. If people join a gym, they are more likely to exercise, thereby increasing the number of Calories that they burn. c: Giving rebates for purchasing fresh fruits and vegetables, may encourage more people to buy these foods, which are naturally lower in Calories than many other foods, and this may lead to an overall decrease in the number of Calories consumed. d: By encouraging teachers to instruct young students about diet and nutrition, children may start to exercise more, to request healthier foods (or be more accepting of healthier foods), and may also bring some of the information that they learn home to their parents.
If the French eat meals with a higher fat content, why don’t the French weigh more on average than Americans?
There are many possibilities, including eating smaller portions (and thus consuming fewer Calories) overall; spending more time at meals (allowing time for the body to sense that it is “full”); snacking less between meals, and perhaps engaging in more daily activity.
INTERPRETING DATA
Look at the illustration on page 130 showing the increase in size and calorie content for different foods in the past several decades.
Calculate the % increase in Calorie content of a typical serving of the foods shown in the past 20 years. Which food has had the greatest increase in Calories in the past 20 years? Which has had the smallest increase in the past 20 years?
a: The calculations are made as follows: [(today’s Calorie content – former Calorie content)/former Calorie content] ×100. The cheeseburger is thus [(590 – 333)/333] ×100 = 77% heftier in terms of Calories. The fries have 190% more Calories, the turkey sandwich has 156% more Calories, the bagel has 150% more Calories, and the soda has 194% more Cals.
Driving Question 2
How does the body use the energy in food?
By answering the questions below and studying Infographics 6.4 and 6.5 and Table 6.1, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
Which type of organic molecule stores the most energy per gram?
a. proteins
b. starch
c. nucleic acid
d. fats (triglycerides)
e. glycogen
d
A moderately active 21-year-old female has a choice of eating a 2,500-Calorie meal that is primarily protein or a 2,500-Calorie meal that is primarily sugar. What would be the result, in terms of energy, of choosing one over the other?
a. Nothing; she would burn all these Calories, given her age, gender, and activity level.
b. She would store the excess Calories as protein, regardless which meal she ate.
c. She would store the excess Calories as protein if she ate the protein meal, and as glycogen if she ate the sugar meal.
d. In either case, once her glycogen stores are replenished, she will store the excess Calories as fat.
e. Regardless of the number of Calories, she will get more energy from the sugar meal.
d
If you exercise for an extended period of time, you will use energy first from________, then from _______.
a. fats; glycogen
b. proteins; fats
c. glycogen; proteins
d. fats; proteins
e. glycogen; fats
e
MINI CASE
Consider a well-trained 130-pound female marathon runner. She has just loaded up on a carbohydrate meal and has the maximum amount of stored glycogen (6.8 g of glycogen per pound of body weight).
a. How many grams of glycogen is she storing?
b. How many Calories does she have stored as glycogen?
c. If this same number of Calories were stored as fat, how much would it weigh?
d. Suppose she decides to go for a run at a pace of 9 miles per hour (she will be running 6.5-minute miles). Given her weight, she will burn 885 Calories per hour at this pace. How long will it take her to deplete her glycogen stores? How many miles can she run before her glycogen supplies run out? Will she be able to complete a 26.2-mile marathon?
e. Once her glycogen supplies run out, what has to happen if she wants to keep running?
a: 130 pounds × 6.8 g glycogen per pound = 884 g. b: She has 884 grams glycogen × 4 Calories/g = 3,536 Calories stored as glycogen. c: Each g of fat stores 9 Calories, so 3,536 Calories could be stored in only 393 g of fat (compared to 884 g of glycogen). d: She has 3,536 Caloriess stored as glycogen. If she is burning 885 Calories per hour, she can run 4 hours on her glycogen stores. At this pace (9 miles per hour), she can run 36 miles on her glycogen—a distance greater than a marathon (26.2 miles). e: She will start to burn other energy sources, which include fats and proteins.
Driving Question 3
How does aerobic respiration extract useful energy from food?
By answering the questions below and studying Infographics 6.6, 6.7, 6.8, and 6.10, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
Which process is not correctly matched with its cellular location?
a. glycolysis—cytoplasm
b. citric acid cycle—mitochondria
c. glycolysis—mitochondria
d. electron transport—mitochondria
e. none of the above; they are all correctly matched
c
In the presence of oxygen we use ________ to fuel ATP production. What process do plants use to fuel ATP production from food?
a. aerobic respiration; photosynthesis
b. aerobic respiration; aerobic respiration
c. fermentation; aerobic respiration
d. fermentation; photosynthesis
e. glycolysis; photosynthesis
b
Given 1 g of each of the following, which would yield the greatest amount of ATP by aerobic respiration?
a. fat
b. protein
c. carbohydrate
d. nucleic acid
e. alcohol
a
During aerobic respiration, what molecule has (and carries) electrons stripped from food?
a. NAD+
b. NADH
c. O2
d. H2O
e. pyruvate
b
During aerobic respiration, how does NADH give up electrons to regenerate NAD+?
a. by giving electrons to O2
b. by giving electrons to pyruvate
c. by giving electrons to glucose
d. by giving electrons to the electron transport chain
e. by giving electrons to another NAD+
d
USE IT
Draw a carbon atom that is part of a CO2 molecule such as you just exhaled. Using a written description or a diagram, trace what happens to that carbon atom as it is absorbed by the leaf of a spinach plant and then what happens to the carbon atom when you eat that leaf in a salad.
The carbon atom (in the form of CO2 in the air) will be taken up by the spinach leaf and used to make sugars (glucose) by photosynthesis, which occurs in the chloroplasts in the leaves. The sugar may be used to build cell wall material (cellulose) in the plant, or it may be used in aerobic respiration in the plant to generate ATP to power cellular functions, or it may be stored as starch (a polymer of glucose). When humans eat the spinach, they can digest the starch, and then “burn” the released glucose in aerobic respiration. The carbon atoms will be released (and exhaled) as CO2, back into the air—so will have come full circle.
If you ingest carbon in the form of sugar, how is that carbon released from your body?
a. as sugar
b. as fat
c. as CO2
d. as protein
e. in urine
c
Driving Question 4
When does fermentation occur, and why can’t it sustain human life?
By answering the questions below and studying Infographic 6.9, you should be able to generate an answer for the broader Driving Question above.
KNOW IT
Compared to aerobic respiration, fermentation produces ________ ATP.
a. much more
b. the same amount of
c. a little less
d. much less
e. no
d
What process is most directly prevented in the absence of adequate oxygen?
a. citric acid cycle
b. glycolysis
c. electron transport chain
d. a, b, and c
e. glycolysis and the citric acid cycle
c
During fermentation, how does NADH give up electrons to regenerate NAD+?
a. by giving electrons to O2
b. by giving electrons to pyruvate
c. by giving electrons to glucose
d. by giving electrons to the electron transport chain
e. by giving electrons to another NAD+
b
Where in the cell does fermentation take place?
a. cytoplasm
b. mitochondria
c. nucleus
d. cytoplasm and mitochondria
e. Fermentation doesn’t occur in cells, it occurs in circulating blood.
a
USE IT
Explain how the presence or absence of oxygen affects ATP production. (The terms aerobic respiration and fermentation should be in your answer.)
In the presence of oxygen, fuels (such as glucose) will be “burned” (that is, broken down) by aerobic respiration. This process includes glycolysis, the citric acid cycle, and the electron transport chain. When this process runs to completion, approximately 36 molecules of ATP are produced per molecule of glucose. Oxygen is required in order for the electron transport chain to run to completion. In the absence of oxygen, cells rely on fermentation, which produces only two molecules of ATP per molecule of glucose.
Consider fermentation.
a. How much ATP is generated during fermentation?
b. How does this compare to aerobic respiration?
c. In humans, why can’t fermentation sustain life? Hint: Think of two reasons—one is related to the product of fermentation and what happens if it accumulates.
a: Only two molecules of ATP are generated per molecule of glucose. b: This is much less ATP than is produced by aerobic respiration, which produces ~36 molecules of ATP per molecule of glucose. c: Fermentation cannot sustain life for humans, for several reasons. There is not enough ATP produced to sustain all our cellular and body functions, and the product of fermentation is lactic acid. If lactic acid substantially accumulates, it will cause our blood and tissues to acidify, disrupting the structure and function of most proteins. We cannot survive if our internal environment becomes too acidic, and a stable pH cannot be maintained in the presence of sustained lactic acid production.
BRING IT HOME
Losing 1 pound of weight requires a deficit of 3,500 Calories. Design three strategies for someone weighing 150 pounds to lose 1 pound in two weeks. The first should rely on (a healthy) diet alone. The second should rely on exercise alone. The third should be a combination of diet and exercise. Which of the three do you think would be easiest to follow?
Answers will vary. The general principle of weight loss is to take in fewer Calories than are expended. If we consider the hypothetical need to create an overall deficit of 3,500 Calories in 2 weeks, this could be done by diet—by eating 250 fewer Calories per day for 14 days. From data in Table 6.1, this could mean eliminating one grande mocha frappuccino with whipped cream and substituting a 12 oz. glass of nonfat milk. The loss could also be achieved by exercising more, enough to burn 250 additional Calories per day. From data in Table 6.1, this could mean walking for 1 hour at 3 miles per hour or hiking for half an hour each day. Or, caloric intake could be reduced by ~100 Cals per day and activity increased by burning ~150 Calories per day. This could be achieved by cutting out one 12 oz. cola each day and having 2 glasses of unsweetened green tea instead, and adding 30 minutes of walking each day. The last plan (eating slightly less and being somewhat more active) requires only moderate changes to eating and activity levels.