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What Are the Different Types of Cellular Respiration?
Cellular respiration is the process by which cells convert various forms of chemical energy into adenosine triphosphate, or ATP, a molecule that is used to "transport" usable cellular energy. Cellular respiration can proceed by different mechanisms based on the conditions of the cellular environment during the respiration process. Oxygen, for example, is a major factor — respiration proceeds by different mechanisms in aerobic conditions, or conditions in which oxygen is present, than in anaerobic conditions, or conditions in which oxygen is not present. Some organisms are able to switch between aerobic and anaerobic modes of respiration based on the environmental conditions, though in such cases anaerobic respiration is generally not sustainable for a long period of time.
Aerobic respiration is cellular respiration that requires oxygen. Humans and many other organisms make use of this form of respiration because oxygen's chemical properties allow for very efficient energy transfer. The oxygen for aerobic cellular respiration is provided through breathing; when one's oxygen intake is insufficient to provide enough oxygen, short-term anaerobic mechanisms must be used to supplement the aerobic mechanisms.
The raw materials used during the energy-transferring respiration processes are provided through the consumption of food, which is broken down into a chemical form that can be used during the reactions that occur during respiration. It should be noted that cellular respiration itself requires energy, as some ATP is used in order that more may be produced.
In some cases, aerobic cellular respiration is not sufficient to provide all of the energy required for the body's cellular needs. This is common when one engages in athletic practices that heavily tax one's muscles. Aerobic mechanisms are not capable of keeping up with the energy needs of the muscles, so a process referred to as fermentation is activated to supplement the energy production. This process is much less efficient than its aerobic counterpart, producing only two ATP molecules per glucose molecule used, compared to the 38 produced through the aerobic mechanisms. It also produces a great deal of energy-rich waste that cannot be broken down into a usable form through fermentation.
Some organisms live in anaerobic conditions and, accordingly, have cellular respiration processes that do not include oxygen. Some of these organisms will actually die in the presence of oxygen; such organisms are referred to as obligate anaerobes. Most of the organisms that primarily use such cellular respiration mechanisms are small and non-complex, and tend to lack energy needs such as muscular movement and complex digestive processes.
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![Aerobic respiration is cellular respiration that needs oxygen.]()
By: arsdigitalAerobic respiration is cellular respiration that needs oxygen. -
![Both aerobic and anaerobic exercise should be included in a well-designed fitness program.]()
By: Syda ProductionsBoth aerobic and anaerobic exercise should be included in a well-designed fitness program. -
![Cellular respiration is the process by which cells convert various forms of chemical energy into adenosine triphosphate, or ATP.]()
By: molekuul.beCellular respiration is the process by which cells convert various forms of chemical energy into adenosine triphosphate, or ATP. -
![During respiration, glucose molecules react with oxygen molecules and are broken down.]()
By: Sophia WintersDuring respiration, glucose molecules react with oxygen molecules and are broken down. -
![Cellular respiration is the process of cells converting different forms of chemical energy into ATP.]()
By: logos2012Cellular respiration is the process of cells converting different forms of chemical energy into ATP.
Discussion Comments
Can someone explain the difference between photosynthesis and cellular respiration? I know photosynthesis is the process of a plant taking carbon dioxide from the air and turning it into sugar. Cellular respiration was described above, of course.
We always talk about plants taking in carbon dioxide from the atmosphere and releasing oxygen, but wouldn't they also have to use up some oxygen to create ATP? All of the examples we ever talked about in biology class were only about animals. We never talked about the differences in plant respiration.
The article didn't mention it specifically, but aren't mitochondria where cellular respiration takes place? I just want to make sure I am thinking of the right process.
@cardsfan27 - We were just talking about anaerobic fermentation today in my biology class. There are two different types: lactic acid fermentation and alcoholic fermentation.
In humans, and I assume other animals, when we go through anaerobic respiration (like after heavy exercise) our muscles form lactic acid, which is what causes cramps.
In the case of some other anaerobic situations, like with yeast, the byproduct is ethanol, or alcohol. Our professor actually talked about it, that basically beer production is the brewers putting a much of yeast in with the malt and barley and other ingredients. The yeast start to eat those things and give off carbon dioxide gas. Eventually, they all start to suffocate and release alcohol and finally die.
@ - It is kind of difficult to explain without a cellular respiration diagram or something to look at, but I can try to give a brief explanation. Basically, we eat foods that are turned into glucose and other energy containing molecules, plus we breathe in oxygen.
Some ATP is used to break apart the glucose, then the carbons from glucose are sent through a bunch of enzymes that create create reactions that can join phosphorous to ADP (ATP without one of its phosphorous atoms).
The law of thermodynamics about energy creation isn't broken because there was energy expended by a plant to turn carbon dioxide and water into glucose.
As I'm sure you know, it can get much more complicated than that, but those are the basics.
So, the article talks about fermentation happening in anaerobic cellular respiration. Does this have anything to do with the same type of fermentation involved in making alcohol? I doubt it, but it's worth asking I guess.
Something else that I never really understood in my biology classes is how you could get 38 molecules of ATP just from using a few molecules of it. Doesn't that break the law that says you can't create or destroy energy? Obviously it doesn't, somehow, but I never quite understood it. Can someone explain it.
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