Problem 14 - Biology Today and Tomorrow Without Physiology

Question

In the third stage of aerobic respiration, __________ is the final acceptor of electrons from glucose. a. water b. hydrogen c. oxygen d. NADH

Step-by-Step Solution

Answer

Oxygen (c) is the final acceptor of electrons in the third stage of aerobic respiration.

Step 1: Understanding the question

The question asks about the final acceptor of electrons in the third stage of aerobic respiration. This stage is known as the electron transport chain.

Step 2: Revisiting the Electron Transport Chain

In the electron transport chain, electrons are passed through a series of proteins. The final acceptor of these electrons at the end of this chain is crucial for the formation of water.

Step 3: Analyzing the Options

The options provided are: a) water, b) hydrogen, c) oxygen, and d) NADH. We need to determine which among these is the final acceptor of electrons.

Step 4: Identifying the Correct Answer

In the electron transport chain of aerobic respiration, oxygen is the final electron acceptor. It combines with electrons and hydrogen ions to form water, completing the process of cellular respiration.

Key Concepts

Electron Transport Chain

The Electron Transport Chain (ETC) is the final stage of aerobic respiration. It is a sequence of protein complexes located in the inner mitochondrial membrane. In this stage, electrons are transferred from electron carriers like NADH and FADH2 to the chain, through a series of redox (reduction-oxidation) reactions.
These reactions facilitate the pumping of protons across the mitochondrial membrane, creating an electrochemical gradient. The generated gradient powers ATP synthesis through a process known as chemiosmosis, during which ATP synthase, a protein complex, produces ATP, the energy currency of the cell.
In summary, the electron transport chain is critical for energy production and sustains most aerobic organisms by providing the majority of ATP needed for cellular activities.

Oxygen as Electron Acceptor

Oxygen plays a pivotal role in the electron transport chain as the terminal electron acceptor. Its presence is essential because it receives electrons from the last protein complex of the chain, ensuring the chain continues to function efficiently.

• Without oxygen, electrons would back up in the chain, halting the process and reducing ATP production.
• Oxygen combines with the electrons and hydrogen ions (protons) to form water, which is a byproduct of this stage of respiration.

This ability to accept electrons and facilitate water production renders oxygen indispensable to the process of aerobic respiration. Thus, oxygen acts not only as a final electron acceptor but also as a crucial component for maintaining the energy production cycle in aerobic organisms.

Cellular Respiration Process

Cellular respiration is a multi-step process that converts glucose into energy in the form of ATP. It occurs in three main stages:

• Glycolysis, which takes place in the cytoplasm, breaks down glucose into pyruvate, yielding small quantities of ATP and NADH.
• The Citric Acid Cycle (also known as Krebs Cycle), occurring in the mitochondrial matrix, completes the oxidation of glucose components, producing ATP, NADH, and FADH2.
• The Electron Transport Chain, where most ATP is produced, transfers electrons from NADH and FADH2 to oxygen, creating water in the process.

Through these stages, cellular respiration efficiently breaks down glucose to release energy, which is vital for cell functions. Each stage is interconnected, and the efficient transfer and utilization of electrons are crucial to the production of ATP, highlighting the coordinated system that supports life in aerobic organisms.