Aerobic respiration is the aerobic catabolism of nutrients to carbon dioxide, water, and energy. This process occurs in all cells of aerobic organisms.
Aerobic respiration is not commonly called “aerobic catabolism.” It is often called the “Krebs cycle,” which happens in the mitochondria. The Krebs cycle breaks down glucose to synthesize ATP (cellular energy) by oxidizing acetyl-CoA into carbon dioxide and water with the use of oxygen.
Aerobic respiration takes place in the mitochondria. During aerobic respiration, glucose is broken down into pyruvate, which enters the Kreb cycle. Inside of the cell, NADH and FADH are converted to ATP through a series of oxidation-reductions reactions known as the “Krebs cycle.”
These reactions require oxygen and produce carbon dioxide as a product. Finally, water is formed as well when oxygen combines with carbon dioxide.
Here some points are discussed about Aerobic Respiration is the Aerobic Catabolism of Nutrients to Carbon Dioxide-
1. Respiration is not a simple process.
Oxygen combines with carbon dioxide in the mitochondria to release energy and make water. A simple model of aerobic respiration is the Krebs Cycle (below). Here, glucose is broken down into pyruvic acid by glycolysis.
Inside the cell, pyruvic acid enters the Krebs cycle (refer to above article) where it is converted into acetyl-CoA. Acetyl-CoA enters the citric acid cycle where it enters into the TCA cycle where it enters second oxidation reaction and get converted into carbon dioxide and water as products. FADH2 gets converted to NADH that then reduced electron carriers like NADH.
This process is called oxidative phosphorylation. At the end of this reaction, energy is released in the form of ATP that can be used by different cells.
2. Animals, plants, and bacteria all undergo aerobic respiration.
Animals use oxygen for respiration. The mitochondria are found only in animal cells (where oxygen utilization is used). Oxygen combines with glucose in the mitochondria to release energy and make water. Energy is used to power muscles that help animals move around and control metabolic processes such as respiration and digestion of food.
This process is used in plants, as well. Plants use carbon dioxide and water to produce glucose through photosynthesis. It is then converted into sucrose and other sugars that are used as an energy source for the plants.
Bacteria cells use fermentation to produce energy. Fermentation does not require oxygen because there are enough electrons provided by NADH and FADH2 produced from glycolysis and the Krebs cycle.
3. All aerobic respiration cycles are the same except for the Krebs Cycle.
In plants, sucrose is broken down into glucose. Glucose is used as an energy source by plants. In bacteria fermentation occurs when glucose is broken down into pyruvic acid and then reduced to form hydrogen ions and carbon dioxide.
Electrolysis happens in animals to synthesize ATP (cellular energy) from pyruvic acid, carbon dioxide in mitochondria, or oxaloacetate in the cytosol of liver cells, and acidification of respiratory fluids.
4. Oxidation and reduction are the same process but different words are used.
Oxidation is the loss of electrons from a chemical reactant to form a more electronegative form. Reduction is the gain of electrons from a chemical reactant to form a more electronegative form. The electrons that get lost or gained during this process are released energy.
This energy can power the cell by producing ATP or can be used by other parts of the cell to do anaerobic respiration (a process where pyruvic acid is converted into hydrogen ions and carbon dioxide). Cytochromes are proteins inside mitochondria that carry electrons for oxidation and reduction reactions. In aerobic respiration, these proteins are critical because they are responsible for taking electrons from NADH and FADH2 and transferring them to oxygen so it can react with carbon dioxide to make water.
5. Acetyl-CoA is the “driver” of cellular respiration in the TCA cycle.
Acetyl-CoA is produced from pyruvic acid in the catabolic pathway called glycolysis (refer to point. When this is created, pyruvic acid is reduced to two acetyl-CoA molecules and two NADH molecules. The two NADH molecules can be used as an electron carrier to reduce other compounds.
Inside the cell, these acetyl-CoA are then converted into several other compounds that require electrons like fumarate, which absorbs a hydrogen ion in order to get to the TCA cycle. These hydrogen ions are used in anion exchange reactions where they can get absorbed by water to make ATP.