CH 6 Study Guide Answers PDF

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Chapter 6: Dietary Energy and Cellular Respiration: Answer Key Supersize Me?: The biology and culture of our expanding waistlines. Driving Question 1: Why do humans weigh more now than in the past? Why should you care? Well over 50% of American men and women, and an increasing number of American children, are classified as overweight or obese. This means that their body compositions – the proportion of muscle, fat, bone, etc. in their bodies -- include too much fat for their height. Being overweight or obese increases the risk of developing heart disease, diabetes, and some forms of cancer; the current trends are problematic, therefore, both for individuals and for society as a whole. The most common measure of body composition is the Body Mass Index (BMI), a number calculated by using a combination of an individual’s height and weight. BMI must be interpreted with some caution because it is only an indirect measure of body composition: some individuals might register as overweight or obese despite having healthy body compositions. Understanding the reasons why Americans – and people in countries that adopt American eating habits – are increasingly overweight and obese is the first step toward solving the problem. The reasons are complex and include the interaction of our adaptations to a long evolutionary history of food shortage with a modern culture of eating large meals of calorie-dense foods. Which of these factors is easier to change? What should you know? To fully answer this Driving Question, you should be able to: 1. Discuss the aspects of our biological history and modern culture that contribute to the current obesity epidemic and describe the consequences of their interaction. 2. Evaluate the data from Infographic 6.3 in light of the hypothesis that biology and culture interact to contribute to the growing problem of obesity in the United States. Infographic Focus: The infographics most pertinent to the Driving Question are 6.1, 6.2 and 6.3. Test Your Vocabulary: Match the following definitions to the terms they describe: [BODY MASS INDEX (BMI)] An estimate of body fat based on height and weight [OVERWEIGHT] Having a BMI between 25 and 29.9. [OBESE] Having 20% more body fat than is recommended for one’s height, as measured by a body mass index equal to or greater than 30.

1. Discuss the aspects of our biological history and modern culture that contribute to the current obesity epidemic and describe the consequences of their interaction. What feature of our biological history contributes to the obesity problem? Humans have adapted to store extra food as fat for when food is scarce. In developed countries, most people no longer have to worry about famine, but their bodies still store food as if famine was a constant threat. What specific adaptation has resulted from that history? We have adapted to store extra energy (food) as fat. What features of modern American food culture contribute to the obesity epidemic? The American diet largely consists of food that is highly processed, high in fat content and available in large quantities. How do our specific adaptations and modern food culture interact to produce the obesity problem we now face? Since there is an abundance of food, a lot of it unhealthy, available to us, we eat large portions on a day-to-day basis. Our bodies store the excess food we consume as fat, waiting for a famine that will likely never come. 2. Evaluate the data from Infographic 6.3 in light of the hypothesis that biology and culture interact to contribute to the growing problem of obesity in the United States. Can this data be used to test the hypothesis that biology and culture interact to contribute to the obesity problem in the U.S.? Yes, this data could be used to test this hypothesis since there is likely a cultural difference between American and French food portion sizes. Do the data from this study support or falsify the hypothesis that biology and culture interact to contribute to the obesity problem in the U.S.? Explain. This data supports the hypothesis that biology and culture interact to contribute to the obesity problem in the U.S. because the food portion in the U.S. is at least twice as large in almost every restaurant studied. Since there is likely a cultural difference behind this difference, and Americans have a higher rate of obesity than the French, this would support that the interplay of culture and biology are both contributing to the obesity problem. Review Questions 1. True or False: The ability to store food as energy was a useful adaptation when the food supply was uncertain. 2. Why would larger portion sizes potentially lead to a higher rate of obesity? (choose all that apply) a. more food = more fat storage in the body

b. more food = the need to exercise more to “burn off” the extra calorie intake c. more food = increased body metabolism (the ability to burn calories) d. more food = longer time needed to consume it

Driving Question 2: How does the body use the energy in food? Why should you care? Physiologically, we become overweight/obese by consuming more food energy (Calories) than our body needs, and then storing the excess as fat. Foods vary in their energy content because they vary in the proportion of fats, carbohydrates, and proteins they contain. If we know the energy content of different macromolecules and the proportions of those macromolecules in different kinds of foods, we can better control our Calorie intake and, ultimately, our body composition. Our bodies have evolved an efficient way to deal with excess calories (this is good news or bad news, depending on your perspective!). Excess simple sugars are bound into glycogen, a complex carbohydrate, and stored in our muscles and liver. Glycogen is an excellent short-term energy storage molecule because it is quickly broken down. Triglycerides (a type of fat), on the other hand, are better long-term energy storage molecules because they are so energy-dense: a little fat stores a lot of energy. Understanding how energy reserves are stored and mobilized can help with proper nutrition and smart exercise plans. What should you know? To fully answer this Driving Question, you should be able to: 1. List the energy-containing biomolecules and the approximate amount of energy each one contains. 2. Explain the process by which excess nutrients are converted to energy storage molecules. 3. Compare and contrast glycogen and fat as energy storage molecules. Infographic Focus: The infographics most pertinent to the Driving Question are 6.4, 6.5 and Table 6.1. Test Your Vocabulary: Match the following definitions to the terms they describe: [calorie] The amount of energy required to raise the temperature of 1g of water by 1°C. [Calorie] 1,000 calories or 1 kilocalorie (kcal); the capital “C” in Calorie indicates “kilocalorie”. The Calorie is the common unit of energy used in food nutrition labels. [GLYCOGEN] A complex animal carbohydrate, made up of linked chains of glucose molecules, that stores energy for short-term use. [TRIGLYCERIDES] A type of lipid found in fat cells that stores excess energy for longterm use. 1. List the energy-containing biomolecules and the approximate amount of energy each contains.

In the table below, choose the biomolecule, its subunits and its final energy content and mark them with the same letter (A, B, C or D). The first one is filled out as an example. Nucleic Acid __A__ Protein ______ Carbohydrate ______ Fat ______

Amino Acids ______ 4 Calories/gram ______ Fatty Acids and Glycerol ______ Zero __A__ Nucleotides __A__ 9 Calories/gram ______ Simple Sugars ______

4 Calories/gram ______

Nucleic Acid __A__

Amino Acids __B____

Protein __B____

Fatty Acids and Glycerol __D____ Nucleotides __A__

4 Calories/gram __C____ Zero __A__

Carbohydrate ___C___ Fat __D____

Simple Sugars __C____

9 Calories/gram __D____ 4 Calories/gram __B____

2. Explain the process by which excess nutrients are converted to energy storage compounds. Before bears hibernate for the winter (i.e. go into a state of inactivity and metabolic depression, sometimes for months), they eat a large amount of food. Why do they do this? What form of energy storage are they utilizing and what biomolecules are involved? Bears eat an excess amount of food before they hibernate for the winter because they will be relying on their stored energy to help them survive through the winter while they hibernate. Amino acids, fatty acids and glycerol, and simple sugars are all involved in this process. Since the bear’s metabolism is very low during hibernation, it does not require much energy to maintain its body, thus glycogen stores are quickly filled and the excess nutrients get converted to triglycerides which are stored for the long term in fat cells. Many marathon runners “carbo-load” the night before a race, meaning that they eat a meal consisting of a large amount of carbohydrates (like pasta and bread). Why do they do this? What form of energy storage are they utilizing and what biomolecules are involved? Runners are taking advantage of the fact that carbohydrates are broken down into simple sugars, which can be stored as glycogen molecules for short term energy stores. Since they will need a lot of readily available energy for the race, their body will utilize this new short term supply of glycogen to help them get to the finish line. 3. Compare and contrast glycogen and fat as energy storage molecules.

Compare and contrast glycogen and fat as energy storage molecules by completing the table.

Location in which stored Order in which stored (first/second) Amount of energy stored (most/least) Order in which used (first/second)

Glycogen Muscle and Liver cells First

Fat Fat cells (all over body) Second

Least (4 Calories/gram)

Most (9 Calories/gram)

First

Second

Write one or two sentences describing the similarities and differences between glycogen and fat (triglycerides) as energy storage molecules. Both molecules store energy for use by the body. Both are made from the subunits of biomolecules and come from the food that is consumed. Glycogen is consumed primarily by muscle and liver cells for quick bursts of immediate energy while triglycerides are stored in fat cells and are used to provide energy sometime in the future (long term storage). Review Questions 1. Given what you know about the American diet and the percentage of obese citizens, what form of energy storage does many people’s body utilize? a. Short term storage b. Long term storage 2. If you wanted to lower your percentage of body fat, along with exercising, which biomolecule would you avoid eating a lot of? a. Proteins b. Fats c. Carbohydrates d. Nucleic acids 1.

Driving Question 3: How does aerobic respiration extract useful energy from food? Why should you care? Just as you can’t take a bar of gold to a convenience store to buy coffee, our bodies can’t use a complex carbohydrate to fuel muscle contractions or other forms of cellular work. Instead, our cells carry out a complex process of energy conversion that results in the production of ATP, the single molecule that acts as energy “currency” for all living things. Aerobic respiration is a metabolic process that uses oxygen to break down energy-rich food molecules in order to extract and store their energy in the form of ATP. This process takes place when we are at rest, of course, but also when we are performing aerobic exercise. Aerobic exercise is a critical component of weight control because it involves large muscles using up huge amounts of ATP. To keep the ATP supply going, we break down glycogen and fat and use their subunits as the raw material for aerobic respiration. What should you know? To fully answer this Driving Question, you should be able to: 1. Explain the role of ATP in living things. 2. List the major inputs and outputs of aerobic respiration. 3. Describe how the inputs are delivered to cells and the waste products removed. 4. Illustrate, outline and describe the three major stages of aerobic respiration. Infographic Focus: The infographics most pertinent to the Driving Question are 6.6, 6.7, 6.8 and 6.10. Test Your Vocabulary: Match the following definitions to the terms they describe: [ADENOSINE TRIPHOSPHATE (ATP)] The molecule that cells use to power energyrequiring functions; the cell’s energy “currency”. [AEROBIC RESPIRATION] A series of reactions that occurs in the presence of oxygen and converts energy stored in food into ATP. [GLYCOLYSIS] A series of reactions that breaks down sugar into smaller units; glycolysis takes place in the cytoplasm and is the first stage of both aerobic respiration and fermentation. [CITRIC ACID CYCLE] A set of reactions that takes place in mitochondria and helps extract energy (in the form of high-energy electrons) from food; the second stage of aerobic respiration. [NAD+] An electron carrier. NAD+ can accept electrons, becoming NADH in the process. [ELECTRON TRANSPORT CHAIN] A process that takes place in mitochondria and produces the bulk of ATP during aerobic respiration; the third stage of aerobic respiration.

1. Explain the role of ATP in living things.

What is ATP? Adenosine triphosphate is the cell’s energy “currency”. It is the molecule that captures energy in a form that cells can use. How does ATP store energy? ATP stores energy in the bonds between its phosphate groups. How is energy released from ATP? Energy is released when the bonds between the phosphate groups are broken. What do we use ATP for? In short, everything. ATP is the major energy source that powers all the cell’s functions. What primary process is used to convert food energy into ATP? Aerobic respiration. 2. List the major inputs and outputs of aerobic respiration. List the molecules required for aerobic respiration and the molecules that are produced as a result of the process. Molecules that are required: oxygen and glucose. Molecules that are produced: ATP, carbon dioxide and water. 3. Describe how the inputs are delivered to cells and the waste products removed. Describe where inputs originate and how they are delivered to cells. The inputs, oxygen and glucose, are delivered to the cell via the blood stream. Oxygen originates from the air we breathe and glucose originates from the food that we eat. Describe where waste products are generated and how they are removed from cells. The waste products, carbon dioxide and water, are generated inside the mitochondrion of an animal cell when the chemical bonds in glucose are broken. The water is released into the cytoplasm of the cell and used there, while the carbon dioxide is absorbed into the blood stream, travels to the lungs and is expelled from the body. 4. Describe the three major stages of aerobic respiration. Complete the table to compare and contrast the three stages of aerobic respiration:

Glycolysis Citric acid cycle

Location

Inputs

Cell cytoplasm Mitochondria

Glucose Pyruvate, e-

Outputs (including waste products) Pyruvate, ATP, e-

Amount of ATP produced 2

NADH, CO2 and ATP

2

Electron transport

Inner mitochondrial membrane

NADH and oxygen

NAD+, Water and ATP

36

Write a one-sentence description of each stage of aerobic respiration, summarizing the information you have provided above. Glycolysis is the first step of aerobic respiration and happens in the cytoplasm of the cell and converts a glucose molecule to two pyruvate molecules. In this process, 2 ATP molecules are released. The pyruvate molecules produced are then fed into the citric acid cycle, which takes place in the mitochondria and produces 2 ATP molecules, NADH and CO2. In this cycle, the energy that is in the bonds of pyruvate is harvested (by breaking the bonds) and incorporated into an NADH molecule, which carries the energy (in the form of electrons) into the inner mitochondrial membrane. The electrons then go into the third stage of aerobic respiration, the electron transport chain. As the energy rich electrons are passed down the electron transport chain, the energy they release at each step powers the creating of ATP molecules. The final electron acceptor in this chain is oxygen, which is converted to water used by the cell. In the final step, 36 ATP molecules are made. Which of the three stages yields the greatest output of ATP? The electron transport chain. If that stage were blocked (by, for example, a poisonous gas that interfered with its critical enzymes), what would happen? Explain. If the electron transport chain where blocked, the energy rich electrons would be trapped in NADH, the majority of ATP molecules would not be made and oxygen would not be converted to water. All in all, this would be bad news for the cell and the organism as there would not be enough energy to maintain normal cellular functions.

Review Questions 1. Which form of ATP has more stored energy? a. One with three phosphate groups b. One with two phosphate groups 2. True or False: Aerobic respiration can occur without oxygen. 3. Which molecule is critical for the correct functioning of aerobic respiration? a. Carbon dioxide b. Water c. ATP d. NADH

Driving Question 4: When does fermentation occur and why can’t it sustain human life? Why should you care? Fermentation is a metabolic process that, some of our body cells can use it to generate ATP when oxygen is scarce. Sprinters and power lifters train to build up their anaerobic capacity – their ability to power their muscles over relatively short intervals when their bodies cannot supply oxygen rapidly enough for their activities to be fueled aerobically. Because anaerobic activities can only be sustained for a few minutes, they are ineffective (by themselves) for weight control and building heart health. What should you know? To fully answer this Driving Question, you should be able to: 1. Illustrate, outline and describe fermentation. 2. Compare the ATP output from fermentation to the output from aerobic respiration. 3. Explain the role of fermentation in a healthy organism. Infographic Focus: The Infographic most pertinent to the Driving Question is 6.9. Test Your Vocabulary: Match the following definitions to the terms they describe: [FERMENTATION] A series of chemical reactions that takes place in the absence of oxygen and converts some of the energy stored in food into ATP. Fermentation produces far less ATP than does aerobic respiration.

1. Illustrate, outline and describe fermentation. Complete the table to compare and contrast the two stages of fermentation:

Glycolysis Fermentation Reactions

Location

Inputs

Amount of ATP produced

Glucose

Outputs (including waste products) Pyruvate, ATP, e-

Cell cytoplasm Cell cytoplasm

Pyruvate and NADH

NAD+ and lactic acid

0

2

Write a one-sentence description of each stage of fermentation, summarizing the information you have provided above. Glycolysis occurs in the same manner with or without oxygen. In fermentation, glycolysis reaction still brakes down glucose into two pyruvate molecules producing 2 ATP molecules in the process. The electrons from the breakdown of glucose are carried by NADH into the next step of fermentation, the fermentation reactions. These reactions convert NADH into

NAD+ (so the molecule can return to the glycolysis reaction and pick up more electrons) and produce lactic acid which is removed from the cell and into the blood stream. The fermentation reactions do not produce any ATP. 2. Compare the ATP output from fermentation to the output from aerobic respiration. About how many ATP are produced by fermentation? About how many are produced by aerobic respiration? About 2 ATP are produced by fermentation and around 40 ATP are produced through aerobic respiration. The ATP produced throu...