Question

In eukaryotes, aerobic respiration is completed in the _____. a. nucleus c. plasma membrane b. mitochondrion d. cytoplasm

Short answer

Aerobic respiration in eukaryotes is completed in the mitochondrion (b).

Step-by-step solution

Identify the Key Terms

Review the question to understand the main terms involved: 'eukaryotes,' 'aerobic respiration,' and the possible locations mentioned - nucleus, mitochondrion, plasma membrane, and cytoplasm.

Understand Aerobic Respiration

Aerobic respiration is a process that uses oxygen to convert biochemical energy from nutrients into ATP, the energy currency in cells. This process primarily takes place in specific cellular structures in eukaryotes.

Recall the Role of Mitochondria

Mitochondria are known as the powerhouse of the cell, where the major steps of aerobic respiration occur—especially the Krebs cycle and the electron transport chain.

Eliminate Incorrect Options

Since aerobic respiration involves the electron transport chain and oxidative phosphorylation, which occur in the mitochondria, eliminate the options that do not host these processes—nucleus, plasma membrane, and cytoplasm.

Select the Correct Answer

By understanding that the mitochondria are responsible for completing aerobic respiration, we identify (b) mitochondrion as the correct choice.

Key concepts

Aerobic Respiration

Aerobic respiration is an essential biological process that occurs in most eukaryotic cells. It is how cells convert food into energy with the aid of oxygen. This process generates adenosine triphosphate (ATP), which cells use as an energy source. The term "aerobic" refers to the need for oxygen in this process. Aerobic respiration happens in several stages, including glycolysis, the Krebs cycle, and the electron transport chain.

During glycolysis, glucose from food is broken down into pyruvate, releasing a small amount of ATP. This stage does not require oxygen and occurs in the cytoplasm.

• The Krebs cycle, also known as the citric acid cycle, is the next stage, happening in the mitochondria. It processes pyruvate into carbon dioxide, yielding high-energy molecules like NADH and FADH2.

The electron transport chain is the final stage, where most ATP is produced. Here, the energy from NADH and FADH2 is used to pump protons across the inner mitochondrial membrane, creating a gradient that drives the synthesis of ATP. Oxygen serves as the final electron acceptor, combining with electrons and protons to form water. This entire process efficiently converts food energy into a form that cells can use for various activities.

Mitochondria

Mitochondria are fascinating and crucial organelles within eukaryotic cells. Known as the "powerhouses" of the cell, their primary function is to generate ATP through aerobic respiration. They are characterized by their unique double-membrane structure, which is essential in the process of energy conversion.

The outer membrane serves as a boundary, while the inner membrane is extensively folded into structures called cristae. These folds increase the surface area available for chemical reactions, allowing for efficient ATP production.

• Inside the mitochondrion, the matrix houses enzymes essential for the Krebs cycle.
• The inner membrane is where the electron transport chain and ATP synthesis take place.

Mitochondria are also unique because they contain their DNA, separate from the cell's nuclear DNA. This feature suggests that mitochondria may have originated from ancient symbiotic bacteria. Understanding the role of mitochondria in energy production is vital in cell biology, as they support various cellular processes and have roles in cell signaling, differentiation, and apoptosis.

Cellular Respiration

Cellular respiration is the overall process of converting the energy stored in macromolecules into ATP. It is a complex series of metabolic pathways occurring in cells, and it ensures that organisms have the energy needed for survival. There are two main types of cellular respiration: aerobic and anaerobic.

In aerobic respiration, oxygen is present and is utilized to produce ATP in large quantities. As previously discussed, aerobic respiration involves glycolysis, the Krebs cycle, and the electron transport chain. Each step is strategically organized to ensure maximum ATP yield.

• Glycolysis splits a glucose molecule into two pyruvate molecules, releasing ATP and NADH.
• In the presence of oxygen, pyruvate enters mitochondria for further energy extraction during the Krebs cycle and electron transport chain.

Anaerobic respiration occurs when oxygen is not available, producing less ATP. This form of respiration includes processes like fermentation. However, without oxygen, cells depend on alternative methods for energy production, which are generally less efficient than aerobic respiration. Understanding cellular respiration is fundamental for comprehending how living organisms obtain and utilize energy at the cellular level.

Biochemistry

Biochemistry is the study of chemical processes within and related to living organisms. It is an interdisciplinary field bridging biology and chemistry, particularly concerning cellular components and functions. Central to biochemistry is the investigation of how energy is harvested, stored, and consumed, making it a crucial part of understanding cellular respiration.

Biochemists explore various biomolecules such as proteins, lipids, carbohydrates, and nucleic acids. Each plays a vital role in cellular processes. For example, enzymes, which are proteins, catalyze reactions in cellular respiration, ensuring these processes occur efficiently and effectively.

• Carbohydrates like glucose serve as primary energy sources for cells.
• Lipids contribute to membrane structure and energy storage.

Biochemistry also examines how cells regulate these processes, which involves a deep understanding of metabolic pathways and energy production shifts in conditions like low oxygen. By studying these intricate chemical pathways, biochemists provide insights into cellular health, dysfunctions, and potential therapeutic approaches to address metabolic disorders.