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Ch. 5 - Microbial Metabolism
All textbooksTortora 14th EditionCh. 5 - Microbial MetabolismProblem 5.1a
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Chapter 5, Problem 5.1a

Which substance in the following reaction is being reduced?
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a. acetaldehyde
b. NADH
c. ethanol
d. NAD⁺

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1
Identify the concept of reduction in a chemical reaction, which involves the gain of electrons by a molecule, atom, or ion.
Examine the given options: acetaldehyde, NADH, ethanol, and NAD⁺.
Consider the role of NADH and NAD⁺ in redox reactions, where NAD⁺ is typically reduced to NADH by gaining electrons.
Analyze the reaction context, where acetaldehyde is often reduced to ethanol by gaining electrons and hydrogen ions.
Determine which substance gains electrons in the reaction, indicating it is being reduced.

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Key Concepts

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

Reduction in Redox Reactions

Reduction is a chemical process where a substance gains electrons, leading to a decrease in its oxidation state. In redox reactions, one species is oxidized (loses electrons) while another is reduced (gains electrons). Understanding this concept is crucial for identifying which substance is being reduced in a given reaction.
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Oxidation States

Oxidation states are a way to keep track of electron transfer in chemical reactions. Each element in a compound is assigned an oxidation state based on its electron configuration and bonding. By analyzing the changes in oxidation states of the reactants and products, one can determine which substance is reduced or oxidized.
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Role of NAD⁺ and NADH

NAD⁺ (Nicotinamide adenine dinucleotide) is a coenzyme that acts as an electron carrier in metabolic reactions. When it accepts electrons, it is reduced to NADH. Conversely, when NADH donates electrons, it is oxidized back to NAD⁺. Recognizing the roles of these molecules is essential for understanding the electron transfer processes in biochemical reactions.
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What Happens. to Aerobic Organisms if There's No Oxygen?
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Related Practice
Textbook Question

DRAW IT The artificial sweetener aspartame, or NutraSweet®, is made by joining aspartic acid to methylated phenylalanine, as shown in the following.

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a. What types of molecules are aspartic acid and phenylalanine?

b. What direction is the hydrolysis reaction (left to right or right to left)?

c. What direction is the dehydration synthesis reaction?

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Textbook Question

Use the following diagrams (a), (b), and (c) for question 1.

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c. Show how these pathways are related.

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f. Show where a long-chain hydrocarbon such as petroleum is catabolized.

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Textbook Question

Use the following choices to answer questions 7–10.

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Textbook Question

DRAW IT Using the following diagrams, show each of the following:

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Which of the following reactions produces the most molecules of ATP during aerobic metabolism?

a. glucose → glucose 6-phosphate

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