Respiration is not the same thing as breathing. Breathing is more properly called ventilation. Instead, respiration is a chemical process in which energy is released from food substances, such as glucose - a sugar.
Aerobic means “with air”. This type of respiration needs oxygen for it to occur so it is called aerobic respiration. Most of the chemical reactions involved in the process happen in tiny objects inside the cell cytoplasm, called mitochondria. when a cell needs to release energy, the cytoplasm (a substance between a cell's nucleus and its membrane) and mitochondria( organelles in cytoplasmthat help with metabolic processes) initiate chemical exchange that launch the breakdown of glucose. This sugar is carried through the blood and stored in the body as a fast source of energy. The breakdown of glucose into adenosine triphosphate (ATP) releases cabon dioxide (co2), a byproduct that needs to be removed from the body. in plants, the energy-releasing process of photosynthesis uses co2 and releases oxygen as its byproduct.
This is the equation for aerobic respiration:
glucose + oxygen ? carbon dioxide + water (+ energy)
The energy released by respiration is used to make large molecules from smaller ones. In plants, for example, sugars, nitrates and other nutrients are converted into amino acids. Amino acids can then join together to make proteins. The energy is also used:
- To allow muscles to contract in animals
- To maintain a constant body temperature in birds and mammals
Fermentation
When sugar molecules (primarily glucose, fructose, and sucrose) break down in anaerobic respiration, the pyruvate they produce remains in the cell. Without oxygen, the pyruvate is not fully catalyzed for energy release. Instead, the cell uses a slower process to remove the hydrogen carriers, creating different waste products. This slower process is called fermentation. When yeast is used for anaerobic breakdown of sugars, the waste products are alcohol and CO2. The removal of CO2 leaves ethanol, the basis for alcoholic beverages and fuel. Fruits, sugary plants (e.g., sugarcane), and grains are all used for fermentation, with yeast or bacteria as the anaerobic processors. In baking, the CO2 release from fermentation is what causes breads and other baked products to rise.
Krebs Cycle
The Krebs Cycle is also known as the citric acid cycle and the tricarboxylic acid (TCA) cycle. The Krebs Cycle is the key energy-producing process in most multicellular organisms. The most common form of this cycle uses glucose as its energy source.
During a process known as glycolysis, a cell converts glucose, a 6-carbon molecule, into two 3-carbon molecules called pyruvates. These two pyruvates release electrons that are then combined with a molecule calledNAD+ tto form NADH and two molecules of adenosine triphosphate (ATP).
These ATP molecules are the true "fuel" for an organism and are converted to energy while the pyruvate molecules and NADH enter the mitochondria. That's where the 3-carbon molecules are broken down into 2-carbon molecules called Acetyl-CoA and CO2. In each cycle, the Acetyl-CoA is broken down and used to rebuild carbon chains, to release electrons, and thus to generate more ATP. This cycle is more complex than glycolysis, and it can also break down fats and proteins for energy.
As soon as the available free sugar molecules are depleted, the Krebs Cycle in muscle tissue can start breaking down fat molecules and protein chains to fuel an organism. While the breakdown of fat molecules can be a positive benefit (lower weight, lower cholesterol), if carried to excess it can harm the body (the body needs some fat for protection and chemical processes). In contrast, the breaking down of the body's proteins is often a sign of starvation.
References:
http://www.diffen.com/difference/Aerobic_Respiration_vs_Anaerobic_Respiration#Fermentation
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