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Ch. 9 - Cellular Respiration and Fermentation
Freeman - Biological Science 7th Edition
Freeman7th EditionBiological ScienceISBN: 9783584863285Not the one you use?Change textbook
All textbooksFreeman 7th EditionCh. 9 - Cellular Respiration and FermentationProblem 8
Chapter 9, Problem 8

Explain the relationship between electron transport and oxidative phosphorylation. How do uncoupling proteins 'uncouple' this relationship in brown adipose tissue?

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Understand the process of oxidative phosphorylation: Oxidative phosphorylation is a metabolic pathway that uses energy released by the oxidation of nutrients to produce adenosine triphosphate (ATP). This process occurs in the mitochondria and involves the electron transport chain, where electrons are transferred through a series of complexes to molecular oxygen, forming water.
Recognize the role of the electron transport chain: The electron transport chain creates a proton gradient across the mitochondrial inner membrane by pumping protons from the mitochondrial matrix to the intermembrane space. This gradient creates an electrochemical potential difference, which is used by ATP synthase to synthesize ATP from ADP and inorganic phosphate.
Learn about uncoupling proteins: Uncoupling proteins (UCPs) are found in the mitochondrial inner membrane and can disrupt the proton gradient established by the electron transport chain. They do this by allowing protons to re-enter the mitochondrial matrix without passing through ATP synthase, effectively 'uncoupling' the proton gradient from ATP synthesis.
Explore the function of uncoupling proteins in brown adipose tissue: In brown adipose tissue, uncoupling proteins, particularly UCP1, play a crucial role in thermogenesis. By uncoupling oxidative phosphorylation, these proteins allow for the energy from electron transport to be released as heat rather than being used to synthesize ATP. This process is vital for maintaining body temperature in cold environments.
Connect the concepts: The relationship between electron transport and oxidative phosphorylation is tightly linked by the production of ATP. Uncoupling proteins, by dissipating the proton gradient as heat, uncouple this relationship, which is especially significant in brown adipose tissue for heat generation rather than ATP production.

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Key Concepts

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

Electron Transport Chain (ETC)

The Electron Transport Chain is a series of protein complexes located in the inner mitochondrial membrane that facilitate the transfer of electrons derived from NADH and FADH2. As electrons move through these complexes, they release energy, which is used to pump protons (H+) from the mitochondrial matrix into the intermembrane space, creating a proton gradient essential for ATP synthesis.
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Oxidative Phosphorylation

Oxidative phosphorylation is the process by which ATP is produced using the energy generated from the electron transport chain. The proton gradient created by the ETC drives protons back into the mitochondrial matrix through ATP synthase, a process that synthesizes ATP from ADP and inorganic phosphate. This coupling of electron transport and ATP production is crucial for cellular energy metabolism.
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Uncoupling Proteins (UCPs)

Uncoupling proteins are a group of mitochondrial proteins that disrupt the proton gradient established by the electron transport chain. In brown adipose tissue, UCPs allow protons to re-enter the mitochondrial matrix without passing through ATP synthase, leading to the release of energy as heat instead of ATP. This process is vital for thermogenesis, particularly in maintaining body temperature in cold environments.
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Related Practice
Textbook Question

In step 3 of the citric acid cycle, the enzyme isocitrate dehydrogenase is regulated by NADH. Compare and contrast the regulation of this enzyme with the regulation of phosphofructokinase in glycolysis.

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Textbook Question

Explain the relationship between electron transport and oxidative phosphorylation. How do uncoupling proteins 'uncouple' this relationship in brown adipose tissue?

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Textbook Question

The researchers who observed that magnetite was produced by bacterial cultures from the deep subsurface carried out a follow-up experiment. These biologists treated some of the cultures with a drug that poisons the enzymes involved in electron transport chains. In cultures where the drug was present, no more magnetite was produced. Does this result support or undermine their hypothesis that the bacteria in the cultures perform cellular respiration? Explain your reasoning.

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Textbook Question
The researchers who observed that magnetite was produced by bacterial cultures from the deep subsurface carried out a follow-up experiment. These biologists treated some of the cultures with a drug that poisons the enzymes involved in electron transport chains. In cultures where the drug was present, no more magnetite was produced. Does this result support or undermine their hypothesis that the bacteria in the cultures perform cellular respiration? Explain your reasoning.
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Textbook Question

Cyanide (C ≡ N−) blocks complex IV of the electron transport chain. Suggest a hypothesis for what happens to the ETC when complex IV stops working. Your hypothesis should explain why cyanide poisoning in humans is fatal.

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Textbook Question

Early estimates suggested that the oxidation of glucose via aerobic respiration would produce 38 ATP. Based on what you know of the theoretical yields of ATP from cellular respiration, show how this total was determined. Why do biologists now think this amount of ATP per molecule of glucose is not achieved in cells?

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