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Ch. 9 - Cellular Respiration and Fermentation
Freeman - Biological Science 8th Edition
Freeman8th EditionBiological ScienceISBN: 9780138276263Not the one you use?Change textbook
All textbooksFreeman 8th EditionCh. 9 - Cellular Respiration and FermentationProblem 5
Chapter 9, Problem 5

Compare and contrast substrate-level phosphorylation and oxidative phosphorylation.

Verified step by step guidance
1
Step 1: Understand the terms: Substrate-level phosphorylation and oxidative phosphorylation are two different ways cells generate ATP. ATP, or adenosine triphosphate, is the main energy currency of the cell.
Step 2: Define substrate-level phosphorylation: Substrate-level phosphorylation is a type of ATP synthesis that occurs when an enzyme directly transfers a phosphate group from a substrate molecule to ADP, creating ATP. This process occurs in the cytoplasm during glycolysis and in the mitochondrion during the Krebs cycle.
Step 3: Define oxidative phosphorylation: Oxidative phosphorylation is a process that uses energy released by the electron transport chain to power ATP synthesis. It occurs in the mitochondria during cellular respiration. Here, electrons are transferred from electron donors to electron acceptors such as oxygen, in redox reactions. These reactions release energy, which is used to form ATP.
Step 4: Compare and contrast: Both processes generate ATP but in different ways and at different stages of cellular respiration. Substrate-level phosphorylation directly transfers a phosphate group to ADP to form ATP, while oxidative phosphorylation uses energy from the electron transport chain to add a phosphate group to ADP. Substrate-level phosphorylation occurs during glycolysis and the Krebs cycle, while oxidative phosphorylation occurs during the electron transport chain.
Step 5: Summarize: In summary, substrate-level phosphorylation and oxidative phosphorylation are both crucial for ATP synthesis, but they differ in their mechanisms and stages of occurrence during cellular respiration.

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Key Concepts

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

Substrate-Level Phosphorylation

Substrate-level phosphorylation is a metabolic process that directly generates ATP by transferring a phosphate group from a substrate molecule to ADP. This occurs in specific enzymatic reactions, primarily during glycolysis and the citric acid cycle. Unlike oxidative phosphorylation, it does not involve the electron transport chain and is less efficient in terms of ATP yield.
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Oxidative Phosphorylation

Oxidative phosphorylation is a process that produces ATP through the electron transport chain and chemiosmosis, occurring in the mitochondria. Electrons from NADH and FADH2 are transferred through a series of proteins, creating a proton gradient that drives ATP synthesis via ATP synthase. This method is more efficient than substrate-level phosphorylation, yielding significantly more ATP per glucose molecule.
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ATP Yield Comparison

The comparison of ATP yield between substrate-level and oxidative phosphorylation highlights their efficiency differences. Substrate-level phosphorylation typically produces 2 ATP molecules per glucose during glycolysis and the citric acid cycle, while oxidative phosphorylation can yield approximately 28-34 ATP molecules per glucose, depending on the efficiency of the electron transport chain. Understanding this difference is crucial for grasping cellular energy production.
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Related Practice
Textbook Question

What does the chemiosmotic hypothesis claim?

a. ATP is generated using phosphates taken from intermediates in the electron transport chain.

b. ATP is generated using a phosphate gradient produced by glycolysis and the citric acid cycle.

c. ATP is generated using a proton-motive force that is produced by the electron transport chain.

d. Water is generated using electrons taken from NADH and FADH2 and transported through the electron transport chain.

Textbook Question

After glucose is fully oxidized by glycolysis, pyruvate processing, and the citric acid cycle, where is most of its energy stored?

Textbook Question

Which of the following correctly describe the fermentation pathway? Select True or False for each statement.

T/FIt includes a reaction that oxidizes NADH to NAD+.

T/FIt synthesizes ATP by substrate-level phosphorylation.

T/FIt includes a reaction that reduces NAD+ to NADH.

T/FIt synthesizes electron acceptors, so that cellular respiration can continue.

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Textbook Question

If you were to expose cells that are undergoing aerobic respiration to a radioactive oxygen isotope in the form of O2, which of the following molecules would you expect to be radiolabeled?

a. Pyruvate

b. Water

c. NADH

d. CO2

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?