Cellular Respiration

Definition

Cellular respiration is the biochemical process by which cells convert glucose and oxygen into energy, specifically ATP (adenosine triphosphate), while producing carbon dioxide and water as byproducts. This process is crucial for maintaining cellular functions, as ATP serves as the main energy currency of the cell, fueling various metabolic activities. The efficiency of cellular respiration is closely tied to the structure and function of cellular organelles, particularly mitochondria, which are known as the powerhouse of the cell.

5 Must Know Facts For Your Next Test

1. Cellular respiration occurs in three main stages: glycolysis, the Krebs cycle (or citric acid cycle), and oxidative phosphorylation.
2. During glycolysis, one molecule of glucose is broken down into two molecules of pyruvate, yielding a net gain of 2 ATP.
3. The Krebs cycle takes place in the mitochondria and produces electron carriers NADH and FADH2, which are crucial for the next stage of cellular respiration.
4. Oxidative phosphorylation involves the electron transport chain and chemiosmosis, where the majority of ATP (about 34 molecules) is generated through a series of redox reactions.
5. In addition to glucose, other macromolecules like fats and proteins can also be used in cellular respiration after being converted into intermediates that enter the metabolic pathways.

Review Questions

• How does glycolysis contribute to cellular respiration and what are its end products?
  • Glycolysis is the initial step in cellular respiration that occurs in the cytoplasm, breaking down one molecule of glucose into two molecules of pyruvate. This process generates a small net gain of 2 ATP and produces 2 molecules of NADH. These end products are essential for subsequent stages; pyruvate enters the mitochondria for further processing in the Krebs cycle, while NADH carries electrons to the electron transport chain for ATP production.
• Discuss the role of mitochondria in cellular respiration and how their structure supports their function.
  • Mitochondria play a central role in cellular respiration by hosting key processes such as the Krebs cycle and oxidative phosphorylation. Their unique double membrane structure increases surface area; the inner membrane contains proteins essential for the electron transport chain and ATP synthase. This allows for efficient ATP production through chemiosmosis as protons are pumped across the membrane, creating a gradient that drives ATP synthesis. Thus, their structure is perfectly suited for energy conversion.
• Evaluate how different conditions affect cellular respiration and its efficiency in generating ATP.
  • Cellular respiration can be significantly influenced by factors such as oxygen availability and substrate type. Under aerobic conditions, cells efficiently generate up to 38 ATP from one glucose molecule; however, under anaerobic conditions, such as intense exercise or hypoxia, cells resort to fermentation pathways that yield only 2 ATP per glucose. Additionally, when different substrates like fats or proteins are used instead of glucose, it alters metabolic pathways but can still provide energy. Understanding these variations highlights how cells adapt their energy production methods based on environmental conditions.

Related terms

Aerobic Respiration: A type of cellular respiration that requires oxygen to produce ATP, yielding a higher amount of energy compared to anaerobic processes.

Glycolysis: The first stage of cellular respiration where glucose is broken down into pyruvate, producing a small amount of ATP and NADH in the process.

Mitochondria: Organelles known as the powerhouses of the cell, where the majority of ATP is produced during aerobic cellular respiration.