Chapter 4. Chapter 6: Dietary Energy and Cellular Respiration

4.1 Introduction

Interactive Study Guide
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Polaris Trail

Welcome to the Interactive Study Guide for Chapter 6: Dietary Energy and Cellular Respiration! This Study Guide will help you master your understanding of the chapter's Driving Questions, using interactive Infographics and activities, as well as targeted assessment questions. Click "Next" to get started, or select a Driving Question from the drop-down menu to the right.

Supersize Me?

The biology and culture of our expanding waistlines

DRIVING QUESTIONS

  • Why do humans weigh more now than in the past?
  • How does the body use the energy in food?
  • How does aerobic respiration extract useful energy from food?
  • When does fermentation occur, and why can’t it sustain human life?

4.2 Driving Question 1

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 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.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
kZ0EESafcHVHlEQ1rns+DGVKyougx1K5opPFAScEtv0CaNdczm3hZw== Having a BMI between 25 and 29.9.
dLKfcwYrAvdAvOIuO73a/k/bl3F2RUgZA2tV+nrjSDnYhHn8xQXqTw== 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.
mawfZQQHySU5UUfRO3RSKPxcD5NXI5wxtgfVfGdUmgC9RAZEhIYiSw== An estimate of body fat based on height and weight
Table
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Correct.
Incorrect.

Discuss the aspects of our biological history and modern culture that contribute to the obesity epidemic and describe the consequences of their interaction.

Question 4.1

5u1Pqr7Ta941l/YN8IYr6Pj+Y1zK9Jcxdfp3uk1sidUd6wTFdFAikS++joA/UUhU/TG4QoKURGFVaaYMTCy5abOxCSXw7Cs40WaSgQnGvmU=
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 were a constant threat.

Question 4.2

TWaEIe5lDO3xlTx268Vhcclb5NkuEhYy4lnEBlZNnoaOH+xKjp+AQD+Mny37wM56d31fhtzi9kKlXOb/
We have adapted to store extra energy (food) as fat.

Question 4.3

1Ffquws+GhOcd8OoocGqKmbtbR1OjDOkX8enwp8gA7XONKzaMx0mi6WHxjDJZW+gA92rpzOAOf7PtZTVMzt7hugm2d8hGicv/NMR/3OmLv+T+vu7so9J/A==
The American diet largely consists of food that is highly processed, high in fat content, and available in large quantities.

Question 4.4

7ZD1TKH5LDBCR35X5b2ZC9uLEd16qO1MwaCGh4CM+v/84D9CNy2cp5Afov25lvYuznLGOjLxeNseXTTz1acdw8Uh44SlWxCvvvWYe75Asask+B7pvKaSZ/RcUPQiDzK04i1F1A==
Since there is an abundance of food, a lot of it unhealthful, 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.

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.

Question 4.5

5lApMNI4OTKqwGRv0aVavvKM8Gi+S2fNRDWd9nXcqcU6/1OIz4fptg7x3PI3Q4saF8/s6VyXZfu6wMhUJ03eAQHX40q53tUbXCLaKty1ONnBDGAe2l4hqztSmwU6UY3SMikOf3P3ZpzfvPUI+tkSCX1Q9uLGf0ujzOhAOQerIhxrabjoZgIO8WF9fpninkHB
Yes, these data could be used to test this hypothesis, since there is likely a cultural difference between U.S. and French food portion sizes.

Question 4.6

1mujLYfuczCvfs1iNmvjZ8wXxncaGCiLhxc8AwpNIFJ0O+D1/Xf6MZ9GWYHHv3/7+rtGSMH66Y2aPIU/Qbptrr+L3xcnbmY17TMW/mhY7tqVJ64P1/Qhkoea+PfGCgLBvqeT5xDkQWGv/Au2I3SD+HvXotWvgIXYF+Frhimll8tC6utYP87Dlozm2YLCQdnIh8lsLkVnEQjAFDguLdwUS/s9B0Gjm67C
These data support the hypothesis that biology and culture interact to contribute to the obesity problem in the United States because the food portion in the United States is at least twice as large as the portion in France in almost every restaurant studied. Since there is likely a cultural difference behind this difference and since Americans have a higher rate of obesity than the French, this supports the hypothesis that culture and biology are both contributing to the obesity problem.

Review Questions

Question 4.7

IiUKEPKFyP5L+WgeVNrTYCVg/HMPlnFfiEL7v/VVGDBXqX6zoG6o/+tvYoyD2HIfvFCKgNNb3Lu/8m8jsvcoBSSUW0X8P750yuN2ZiNAwTkHscmdUu9UXtR3uWsCMzEAbQ36wb3Joudt0VGQcfEqDCNDohb3aXGegVQMkUQPdQoU5fGx
999
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Question 4.8

Why might larger portion sizes lead to a higher rate of obesity? (Choose all that apply.)

a. More food leads to more fat storage in the body. 2YvaXR/y8mhoD5Q0hHYKqg==

b. More food necessitates more exercise to burn off the extra calorie intake. 2YvaXR/y8mhoD5Q0hHYKqg==

c. More food leads to increased body metabolism (the ability to burn calories). kn+fKbLB8wAnmZ3XQAUvWA==

d. More food necessitates more time to consume it. kn+fKbLB8wAnmZ3XQAUvWA==

Correct.
Incorrect.

4.3 Driving Question 2

Driving Question 2

What are essential nutrients?

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 contains.
  2. Explain the process by which excess nutrients are converted to energy storage compounds.
  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.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
TL+BrScQqRjiOtqVijjDnMq+wb7qVz2iiMfXnGs1dPl0ENadKdCf3QqD+AI= 1,000 calories or 1 kilocalorie (kcal); the capital “C” in Calorie indicates
S/o4qHA6+ZykWVCsWHra1M5azNRnBnKu6wnL5br+QOTuY86hLPy2mfsC6fw= The amount of energy required to raise the temperature of 1g of water by 1°C.
RUMAWX2PmkFAYY00ee9IbDpEQe9jm8tyW6/2ygIV9B2fK7Uvnx2R5MH9nWc= A type of lipid found in fat cells that stores excess energy for long-term use.
0BvWgWEpqmmCNTuam5Gr3AgdrTY6PFdMhWL7eortJ3UQIbxZi3gV1Iz3m2s= A complex animal carbohydrate, made up of linked chains of glucose molecules, that stores energy for short-term use.
Table
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List the energy-containing biomolecules and the approximate amount of energy each contains.

Question 4.9

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 Amino Acids zAExGnymgIi51Rp7 4 Calories/gram g1WzeZY0wKtnUx7F
Protein B Fatty Acids and Glycerol khr3seYiJXBWoDnW Zero A
Carbohydrate C Nucleotides A 9 Calories/gram khr3seYiJXBWoDnW
Fat D Simple Sugars g1WzeZY0wKtnUx7F 4 Calories/gram mfpY/rdPtG4UmARh
2
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Explain the process by which excess nutrients are converted to energy storage compounds.

Question 4.10

AmYdaajYd39U+3PccTvvOC92B9+Qy/Oam5rrnUkOceYE6ss0Kkms4LUaCKwzhaCwb7lRTjKWRT+n0o+oWPRCyZVyWGeJb6Aca8jZlospWo+b2YDAxH1QB7Ey5eMzpBaIfBNCXfGbTPpx1D2FDz1gvw1V2ANZONYzKCn27tYAZj8wvGEZ60rwuLOmeiUcy0FXLuEoycJ1Mp7AnOTB89KWCxsZnhO2uQpdhyl10xm5g9FGbQg/e00iiubCWQ9L84n1nNkztRjHd9U3J0TTOPWjM4Fi1GNjIhO8ZjDwaOEa8jYkmpP4/LEA4E6lL1I0uvbOEySddpKGXByt7fyrvg9ncHZ6TCk=
Bears eat a great deal 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 part of this process. Since the bear’s metabolism is very low during hibernation, it does not require much energy to maintain its body, so glycogen stores are quickly filled, and the extra nutrients get converted to triglycerides, which are stored for the long term in fat cells.

Question 4.11

V12E9SuZbOKHC2OMIkgEAHbwP5pCftanRMwMbwI6ZN0ETLGumKScAkkdPdndWBFW3sxCk1KlR7q9q5wKnkuve6EHvj5hPu/DcOYqpwUlK+dghghYU6fyVT/+CKW9/vTZ4VwJlVXXYpkq5Rml63zzr91z4ot8M+uPfe3k2q0Gqp/WbM3huPs+SahyqM55Pza8ORKirjDVR1xFtTy6IOAffCCqBHj4ZbfWGhhHL+jPlQ6M68cFvbgTgPpH959biR0SIZOfB++vjFA0LR9jR8HvVG2o90VbV5y0Tc8lfunloNHShg83wt5Nb3DTyh4+N27/Axp1LgtcX2Sq7rCsOch9FrhzoAux+gdW
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 use this new short-term supply of glycogen to help them get to the finish line.

Compare and contrast glycogen and fat as energy storage molecules.

Compare and contrast glycogen and fat as energy storage molecules.

Question 4.12

Glycogen Fat
Location of storage gzSKVBDrvH01RmKU
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Order stored (first/second) gzSKVBDrvH01RmKU
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Amount of energy stored (most/least) gzSKVBDrvH01RmKU
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Order in which used (first/second) gzSKVBDrvH01RmKU
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Correct.
Table
1
Glycogen Fat
Location of storage Muscle and liver cells Fat Cells (all over body)
Order stored (first/second) First Second
Amount of energy stored (most/least) Least (4 calories/gram) Most (9 calories/gram)
Order in which used (first/second) First Second
Table

Question 4.13

8/KleYqalVD07hyciaL1ysy6ixA+5FlIK2zfybdJ/1mteALwTTKEMaUNw12g4IoC7wzVo3APQxyqvE/HuBNLWRLgSuX92YLhhidsoiB0uqyVSU+mnsm3hzwjxDWweGt4IBlvgfrRxCZX3x3P9XVJvCKuu5ghZmilo1C41Hi4vwzVU7zU3eUlT35iNi9YRPAV
Both molecules store energy. 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

Question 4.14

W6/Er2MRTsT5QRXRllqrXEwowejb6QRio7Fs85/YD84Diu8Vjc8kOOh+7iqrQjEqGkOpZ1oa/ZHnvNwUSIh63HUJdp1Od2VYtVbLwd4RG6kis29Ax/HMwK22q5YFfjvMU39TM3GvFuV6ekOZxyCa2Pc8ahKVINUpDWGLU36Qd1NgpsFjZt34n9L6znOSnjxTP0+ADXWoHuuieHH7jg+92JxNxfVMhAo0Aq7pPMqQGD3otrWRN0I/5rb3X3UKxyHjJkY5cOh6ueGChhPFknm3undcMJWa7RCMPS7H1idGJ3nfogJi
1
Correct.
Incorrect.

Question 4.15

q65TDymjrSa7wyhrAzASKTVVqXwOxqShkonT3TDZZh59FQ7Z/pqhFOIHnVntXOtrqPijK4x3JUXGnRZequ/2HY7iAzvrO4fzbC401LFt/fKmlc4XepTrceRQ+rz3jYoqcdk2d/QLU7AZhl3X83k5hRYYdKsrjYnRXtIG/Ic6EIRgmM3KJm9k5AAV/Xjpe84w9qmnmydEYj+bELJXOoNYfvsoDo3V5l6/vjE57rcF6Q86eyDbTqs+Yy1g7Kcq0US4U4DayAsZzJt9ZCPhAVd59g==
2
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4.4 Driving Question 3

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 adenosine triphosphate (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. 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.

Question Test Your Vocabulary

Choose the correct term for each of the following definitions:

Term Definition
Qwc8vTgSjwqFRaYV1wecMmXRr3Hyo1abSRaRsmclvaGKU+PcBPf93fm+grvdQZWGaEEW//T/Iu54svRHl8+6w0ah4O7+yiK88aVHLOCPYYOeibO5geok56WwozXEtHD0dhb3S+FWBBsCcZ/hMT2getaijk1qqB3Rqgv2vXKQj2LOJQ3L6tePPGplHrE= 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.
c6N3wSrymOmq/Wq2QrhyHwnlD5xRUFeaD3YQvknbxvLnNdZK712FwnQO9vf2kWRRtO7kEt/0BB0VtDoK4ERu7ceouBwvKMAi603fZ1rHAZDlZjnnnO/jK4i7TzTylaT0Spn60IzvWwb9OCf7o6an+PzWQ5cg1I2ESbrZPjREHaHqZaViDYwu/MKqFNY= The molecule that cells use to power energy-requiring functions; the cell’s energy “currency”.
O8Wt4bIDrpyN6z4YFGOqHjumG+OF6o1sLPwOe/fDgboYEUHb1cc/qclEUnD2aENMhR1VK8Q44xegXUBckF0TeUgjOJFIq8tWwf2GifdrPUqh24kvQwofvLCN6HKM2rn23oU+QalsaGzNJ5fVgShj37fMLrcIrFb05vUKghLe7HM4/0EkLQGzkHq30I4= 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.
QivaM+t3tsHKm5yO/EEChFeJZ29WTuv6itG1JCX5Cz1tD4j8DIhtrL1/593L2ruAzv4DOWHSQeqEG5AyE7auneqXGlV9AjNjdBN27iLveeGtHtsgGJm2wE+cikXA/Yfu+4Fte2aSgwMU6uMgkaraE3VJRqfQwazgJQrM6Q7fgtoXi/cf+nF0AuXlZ2E= A process that takes place in mitochondria and produces the bulk of ATP during aerobic respiration; the third stage of aerobic respiration.
Sa/rqhOKUSUESGWsVjF2NXZk59p/d8PqXhh+Wix1wWAar37ztNOd8tB8WEU9e5atMW1DG4VbcY0qYQqBZ526yEt0dvg4SKC5p8pgyWBPDJm1eRofv0jWYegfjr60YOVQ0tvBdi262vGIcLCDWkckFcSkcDCSojLxyQGHA411p5INgTN9UvRUTCNT1Gg= An electron carrier. NAD+ can accept electrons, becoming NADH in the process.
c1ciGmhaGI4aq25oAG50ubOmXf11wHo6qggLj+IimkL7dTCr97BdDLouu3qo8AousH6qpW83FtmXhdHTxPV8flLN2ZhE9DF25H8AmPYb1FtuIXq0ScK0SOdnX3wKK4o94Fgr2RFnfvnxJ7wBL0Rl6fTTxBFgNyZ+LDTYQ/GheD8Vgi8OMhBslTC2w/8= 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.
qkMLmNe8E1RGwkg+iYIQR3ZjyopWYXacsjUX90l7FyKqLVeaMjTToMpfYGuJm2AiBF2fL5BszCLKAP6lDMkU3ZUBRR0qIWqEN5cm04PfmmfOfYJMV7vRw7Uiw9i9eZw9f8y8ezCjzL4rQIA+WqFzd46zgfnegnvefG0f7yqmcjRAn1qR6rrgfU0xgVw= A series of reactions that occurs in the presence of oxygen and converts energy stored in food into ATP.
Table
2
Try again.
Correct.
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Explain the role of adenosine triphosphate (ATP) in living things.

Question 4.16

5A+Nljvz1QDAJNUhReRqqg==
ATP is the cell’s energy currency. It is the molecule that captures energy in a form that cells can use.

Question 4.17

OBVro3lxReABdG+JAmPDPj2Bc9xzWbwZ2lpaa6M2u78=
ATP stores energy in the bonds between its phosphate groups.

Question 4.18

wmWHmbsERJbQGEA53O3zwkopasvIlB0+7ywX3DoO7b4ARUH7
Energy is released when the bonds between the phosphate groups are broken.

Question 4.19

rY/J/2vmjvet8uTdKKEvu+SP4bdDs8meEh9gsQ==
In short, everything. ATP is the major energy source that powers all of the cell’s functions.

Question 4.20

MkSQQJLyAC7FNolbU46dkUeLfgHywYdQrV5fRua0Hw5eWh9H/sI+Wvj7BKIbC4FXO6bub7O4+lCkDuezAaqm2iU4ARU=
aerobic respiration

List the major inputs and outputs of aerobic respiration.

Question 4.21

0TzZTIy062tJXz2sfkGUcpRl70CQnkMX24iz79245c+s+ZYmLoHy6Yz2CLdIg0a+n2/+RWTsc5we9kIqme4yy8ddJ8cOq+K4ZXrCierM75yLjARDy4DrcCewDdOw7L7etKIFgsoViNlA27BzppH2KMDf3+sEspED
The required molecules are oxygen and glucose. ATP, carbon dioxide, and water are produced.

Describe how the inputs are delivered to cells and the waste products removed.

Question 4.22

Pw1qZuMj48Fz61K40NQ0PWfeAwqPMwoERhA7m9/76P2+Q0b53ScfItnXQzq1LuWZZILAr4PWmbRmt1aIGB3e29zTpksQ2vBr
The inputs, oxygen and glucose, are delivered to the cell in the bloodstream. Oxygen originates from the air we breathe, and glucose originates from the food we eat.

Question 4.23

ExiQfxuB4djVcDNlIc09fMFHk7vUhju3HZbZCoofwGZCO+lMyLzqXpmJwoted3DAwb32U+BYIl8/erLaFLv3817VUCDpqj+U2m9yW78IjOVdFN5p
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 bloodstream, carried to the lungs, and expelled from the body during respiration.

Describe the three major stages of aerobic respiration.

Question 4.24

Complete the table to compare and contrast the three stages of aerobic respiration:

Location Inputs Outputs (including waste products) Molecules of ATP produced
Glycolysis gzSKVBDrvH01RmKU
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Citric acid cycle gzSKVBDrvH01RmKU
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Electron transport gzSKVBDrvH01RmKU
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Table
1
Location Inputs Outputs (including waste products) Molecules of ATP produced
Glycolysis Cell cytoplasm Glucose Pyruvate, ATP, e- 2
Citric acid cycle Mitochondria Pyruvate, e- NADH*, CO2, ATP 2
Electron transport Inner mitochondrial membrane NADH, oxygen NAD, water, ATP 36
Table

*Reduced nicotinic acid dehydrogenase

§Nicotinic acid dehydrogenase

Question 4.25

FS+ZxHwRGmv2/UE2LB3DwC1aSXQyAAh0hvr1pz5N+9L2XPDHgiz3EYAOSiJWBYPfbGZvxaM8O+O16tXQIZaw64VQuAPPYJzZ8vqah0zEC6cND2lzeBr1DYAu8froXnCs9jA+bYO4iV4clhG8tkbDwt1KrgiwuodT1mdL/A==
Glycolysis is the first step of aerobic respiration. It happens in the cytoplasm of the cell, converting a glucose molecule to two pyruvate molecules. In this process, two ATP molecules are released. The pyruvate molecules are fed into the citric acid cycle, which takes place in the mitochondria and produces two ATP molecules, NADH, and carbon dioxide. In this cycle, the energy 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 production 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.

Question 4.26

ElFPQEo0SwxxLXx17zy+eogRJOORS+HVcGW43hvO9lwfvsrpsOsH/f1NkJ7p1/kNvI1ISB/vw3x1wO4niXyxeQ==
the electron transport chain

Question 4.27

02zy+KD7+zel4+5Kx/Ap7j06e3pWsAH4YuQhUT4HjorVqy7QO+mNLdHz4lQlix4S05cHR2b82niZX6EbcyugTEulRblc1aMsPWyd64v0baU4Zdmap07QiHWvB9LDHWUs0bvzPMlSfveexJTEi0B0wT87Lohguap4/SgfE0aT9cO4Vm0/jVQQGQ==
If the electron transport chain is blocked, the energy-rich electrons will be trapped in NADH, most of the ATP molecules will not be made, and oxygen will 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

Question 4.28

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1
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Incorrect.

Question 4.29

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1
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Incorrect.

Question 4.30

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2
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4.5 Driving Question 4

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.

Illustrate, outline, and describe fermentation.

Question 4.31

Complete the table to compare and contrast the two stages of fermentation.

Location Inputs Outputs (including waste products) Molecules of ATP produced
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Fermentation reactions gzSKVBDrvH01RmKU
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Correct.
Table
1
Location Inputs Outputs (including waste products) Molecules of ATP produced
Glycolysis Cell cytoplasm Glucose Pyruvate, ATP, e- 2
Fermentation reactions Cell cytoplasm Pyruvate, NADH NAD+, lactic acid 0
Table

Question 4.32

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Glycolysis occurs in the same manner with or without oxygen. In fermentation, glycolysis reaction still breaks down glucose into two pyruvate molecules, producing two ATP molecules. The electrons from the breakdown of glucose are carried by NADH into the next step of fermentation, the fermentation reactions. These reactions convert NADH to 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 bloodstream. The fermentation reactions do not produce any ATP.

Compare the ATP output from fermentation to the output from aerobic respiration.

Question 4.33

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About two ATP are produced by fermentation and around 40 ATP are produced through aerobic respiration.

Question 4.34

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About 38 ATP are produced by aerobic respiration if the ATP produced by glycolysis is not included. For fermentation, without the ATP produced by glycolysis, no ATP is produced.

Explain the role of fermentation in a healthy organism.

Question 4.35

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Even though fermentation does not produce a large quantity of ATP, it has benefits. Glycolysis happens whether oxygen is present or not. So if you are expending energy and not enough oxygen is available to fuel aerobic respiration (typically when you are expending a lot of energy in short bursts), the cells can use fermentation to produce a small amount of energy to keep you going for a short time. If cells were unable to undergo fermentation, when oxygen was scarce, glycolysis would essentially grind to a halt, and so would you.

Question 4.36

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About 38 ATP are produced by aerobic respiration if the ATP produced by glycolysis is not included. For fermentation, without the ATP produced by glycolysis, no ATP is produced.

Review Questions

Question 4.37

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1
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Question 4.38

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2
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Question 4.39

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2
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Question 4.40

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2
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