Ch. 6 How Cells Harvest Chemical Energy

Taylor - Campbell Biology: Concepts & Connections 10th Edition

Taylor, Simon, Dickey, Hogan10th EditionCampbell Biology: Concepts & ConnectionsISBN: 9780136538783Not the one you use?Change textbook

Taylor, Simon, Dickey, Hogan 10th Edition

Ch. 6 How Cells Harvest Chemical Energy

Problem 10

Chapter 6, Problem 10

Compare and contrast fermentation as it occurs in your muscle cells and in yeast cells.

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Identify the main purpose of fermentation in both muscle cells and yeast cells, which is to regenerate NAD+ from NADH, allowing glycolysis to continue producing ATP in the absence of oxygen.

Explain the process of fermentation in muscle cells, focusing on the conversion of pyruvate into lactate (lactic acid) by the enzyme lactate dehydrogenase, and how this process helps in regenerating NAD+.

Describe the fermentation process in yeast cells, emphasizing the conversion of pyruvate into ethanol and carbon dioxide. Highlight the role of the enzymes pyruvate decarboxylase and alcohol dehydrogenase in this process.

Discuss the conditions under which each type of fermentation occurs, noting that muscle cell fermentation happens during intense exercise when oxygen is scarce, while yeast fermentation occurs in anaerobic conditions such as brewing and baking.

Compare the end products of fermentation in the two cell types, pointing out that lactic acid is the main product in muscle cells, whereas ethanol and carbon dioxide are the primary products in yeast cells.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Fermentation

Fermentation is an anaerobic metabolic process that converts sugars into acids, gases, or alcohol in the absence of oxygen. It allows cells to generate energy when oxygen is scarce. In both muscle and yeast cells, fermentation serves as an alternative pathway for ATP production, albeit with different end products and mechanisms.

Lactic Acid Fermentation

Lactic acid fermentation occurs in muscle cells when oxygen levels are low, leading to the conversion of glucose into lactic acid and ATP. This process is crucial during intense exercise when the demand for energy exceeds the oxygen supply. The accumulation of lactic acid can lead to muscle fatigue, but it allows for continued ATP production.

Alcoholic Fermentation

Alcoholic fermentation is the process by which yeast cells convert glucose into ethanol and carbon dioxide. This type of fermentation is utilized in brewing and baking, where the carbon dioxide produced causes dough to rise. Unlike lactic acid fermentation, alcoholic fermentation results in the production of ethanol, which can be toxic to cells at high concentrations.

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Alcohol Fermentation

Related Practice

Textbook Question

The poison cyanide binds to an electron carrier within the electron transport chain and blocks the movement of electrons. When this happens, glycolysis and the citric acid cycle soon grind to a halt as well. Why do you think these other two stages of cellular respiration stop? (Explain your answer.)

a. They run out of ATP

b. Unused O₂ interferes with cellular respiration

c. They run out of NAD⁺ and FAD

d. Electrons are no longer available

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Textbook Question

In which of the following is the first molecule becoming reduced to the second molecule?

a. Pyruvate → acetylCoA

b. Pyruvate → lactate

c. Glucose → pyruvate

d. NADH + H+ →NAD+ + 2H

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Textbook Question

Which of the three stages of cellular respiration is considered the most ancient? Explain your answer.

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Textbook Question

Explain how your body can convert excess carbohydrates in the diet to fats.

Can excess carbohydrates be converted to protein?

What else must be supplied?

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Textbook Question

An average adult human requires 2,200 kcal of energy per day. Suppose your diet provides an average of 2,300 kcal per day. How many hours per week would you have to walk to burn off the extra calories? Swim? Run? (See Figure 6.4.)

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Textbook Question

Your body makes NAD⁺ and FAD from two B vitamins, niacin and riboflavin. The Recommended Dietary Allowance is 20 mg for niacin and 1.7 mg for riboflavin. These amounts are thousands of times less than the amount of glucose your body needs each day to fuel its energy needs.

Why is the daily requirement for these vitamins so small?

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