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Cellular Respiration: What You Need to Know About Aerobic and Anaerobic Respiration

Everyone has heard of aerobics – they’re the exercises you do when you want to strengthen your lung capacity, improve your overall fitness, and lose weight. The word “aerobic” is defined as being something relating to the intake of oxygen, and aerobic exercises are designed to help your body become more efficient in the absorption of oxygen.

When we talk about aerobic respiration, however, we aren’t simply talking about getting a good workout. Aerobic respiration is a biological function that all humans and a lot of other organisms experience. It’s a metabolic process that uses oxygen molecules to generate energy.

In addition to aerobic respiration, there is also anaerobic respiration, which is the conversion of sugars into energy in environments where oxygen isn’t present.

So, why do we need to know about aerobic and anaerobic respiration?

These phenomena are what allow us to live. Every living thing needs energy to function – human beings need energy to perform the most basic tasks. Breathing is one way we acquire energy, and if we don’t breathe for even a few minutes, we will die. That’s how important energy generation is to survival. Cellular respiration is the process by which energy is transported to our cells so that they can function, grow, and regenerate.

Aerobic respiration is a highly efficient process. It produces a molecule called adenosine triphosphate (ATP), which exists in all living tissues. This molecule delivers the energy necessary for proper cellular activity. The presence of oxygen during aerobic respiration allows for the production of large quantities of ATP because oxygen is a superior electron acceptor to other elements. However, while aerobic respiration produces ATP far more quickly and effectively than anaerobic respiration, human beings experience both. Additionally, anaerobic respiration is a critical process not only in biological functions in the natural world, but also during food production and the generation of some biofuels.


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The Stages of Aerobic Respiration

Living things need energy to function and survive. This energy is sourced by consuming organic and inorganic matter and converting it into energy through cellular respiration. The aerobic respiration process, which we’ll discuss here, requires oxygen. There are four stages of aerobic respiration.

Stage 1. This stage is known as glycolysis. The early glycolysis stage is the initial breakdown of glucose from the carbohydrates in food. This involves the breakdown of glucose molecules by enzymes to form pyruvic acid and nicotinamide adenine dinucleotide (NAD). NAD is an oxidized coenzyme, which can accept electrons. The pyruvic acid is used in later stages of cellular respiration.

Stage 2. The second stage involves the oxidation of pyruvic acid. This process essentially connects the glycolysis stage to the third stage.

Stage 3. The third stage of aerobic respiration is commonly called the Krebs Cycle. This process transforms the pyruvic acid created during glycolysis into an acetyl group known as acetyl-CoA, where high volumes of energy are released to create ATP. This also strips away a carbon molecule, which triggers a reaction that generates hydrogen that bonds with NAD to create NADH. NADH transports electrons to the mitochondria with flavin adenine dinucleotide (FADH2). The Krebs cycle continually breaks down the structure of different molecules to create ATP. This stage also creates carbon dioxide gas, which is exhaled.

Stage 4. The fourth stage is where NADH and FADH2 shuttle electrons to the mitochondria where energy stored within the electrons reacts with oxygen and creates large amounts of ATP during the electron transfer process.

If this seems complicated, it’s because it is! Cellular respiration is a highly complex process that powers all life, and it’s a challenging sequence of events to summarize. However, once you understand the basic steps of cellular respiration, you can better appreciate how a wide variety of life forms grow and function.

The Process of Anaerobic Respiration

Lots of organisms, including humans, experience what is called anaerobic respiration. In organisms that live where oxygen isn’t present, it’s how energy is distributed to their cells using other electron acceptors.

When you work your muscles strenuously, you are likely to experience muscle soreness. That soreness is an example of your body undergoing anaerobic respiration. Anaerobic respiration triggers a process called lactic acid fermentation, and it’s the buildup of lactic acid within our muscles that makes them sore.

Anaerobic respiration differs from aerobic respiration in several ways, including the volume of ATP that anaerobic respiration generates (it’s much lower). However, the most noteworthy way that the process differs is that the byproducts of anaerobic respiration aren’t the same as with aerobic respiration. In fact, anaerobic respiration generates ATP using a fermentation process that is used during lots of different types of food and product production.

Beer, Booze, and Bread

Yeast is a food product that is used to make bread, beer, and alcohol. We enjoy consuming products with yeast because the yeast imparts a pleasant and complex flavor to different foods and beverages while triggering chemical responses necessary to create the products.

Yeast is a single-celled organism that is found in the environment, and it has been used by humans in baking and brewing processes for thousands of years. Yeast colonies use the simple sugars in different grains in the cellular respiration process. When yeast is used in the bread-making process, cellular respiration produces a carbon dioxide byproduct, which expands, causing dough for bread to rise. The alcohol that is also generated is effectively destroyed when the bread is baked.

Speaking of alcohol…

When yeast is put into airtight vessels, the deprivation of oxygen ensures anaerobic respiration (fermentation) which produces alcohol as a byproduct. This is the fermentation process that produces wine and beer, which do not have alcohol concentrates above 30 percent. For liquors like whiskey and vodka, the alcohol generated through fermentation is concentrated through the distillation process.

However, this is a highly specialized process that can lead to mistakes if performed incorrectly. A different kind of fermentation can occur under careless circumstances, producing methanol, which is poisonous if consumed.

We also get another product that starts with the wine-making process – vinegar. After the fermentation that produces wine takes place, an additional process that requires alcohol as fuel must occur. The alcohol is fermented into acetic acid, which gives vinegar its flavor and antibacterial properties.

Say Cheese!

Cheese is another product we know and enjoy thanks to cellular respiration. Cheese undergoes a type of anaerobic respiration process called propionic acid fermentation. This natural process gives Swiss cheese its distinctive nutty flavor and deep holes – the carbon dioxide gasses that result from the fermentation process create bubbles and pockets within the cheese. The bacteria that trigger the propionic acid fermentation are deliberately introduced into the cheese-making process to achieve the product’s characteristic flavor and holes.

The more you know about phenomena like cellular respiration, the more you understand how important the natural world is to our wellbeing and survival. Forest Founders was established to raise awareness of the dangers of deforestation, and support initiatives that protect our green spaces throughout the world. To learn more about Forest Founders’ mission, please visit our information page. To join us in our fight to protect global forests, please register on our signup page.