37 4.11 Anaerobic Processes
Created by: CK-12/Adapted by Christine Miller
Fast and Furious
These sprinters’ muscles will need a lot of energy to complete this short race, because they will be running at top speed. The action won’t last long, but it will be very intense. The energy each sprinter needs can’t be provided quickly enough by aerobic cellular respiration. Instead, their muscle cells must use a different process to power their activity.
Making ATP Without Oxygen
Living things’ cells power their activities with the energy-carrying molecule ATP (adenosine triphosphate). The cells of most living things make ATP from glucose in the process of cellular respiration. This process occurs in three stages: glycolysis, the Krebs cycle, and electron transport. The latter two stages require oxygen, making cellular respiration an aerobic process. When oxygen is not available in cells, the ETS quickly shuts down. Luckily, there are also ways of making ATP from glucose which are anaerobic, which means that they do not require oxygen. These processes are referred to collectively as anaerobic respiration.
Fermentation
Ome important way of making ATP without oxygen is fermentation. Fermentation starts with glycolysis, which does not require oxygen, but it does not involve the latter two stages of aerobic cellular respiration (the Krebs cycle and electron transport). There are two types of fermentation: alcoholic fermentation and lactic acid fermentation. We make use of both types of fermentation using other organisms, but only lactic acid fermentation actually takes place inside the human body.
Alcoholic Fermentation
Alcoholic fermentation is carried out by single-celled fungi (called yeasts), as well as some bacteria. We use alcoholic fermentation in these organisms to make biofuels, bread, and wine. The biofuel ethanol (a type of alcohol), for example, is produced by alcoholic fermentation of the glucose in corn or other plants. The process by which this happens is summarized in the diagram below. The two pyruvic acid molecules shown in the diagram come from the splitting of glucose in the first stage of the process (glycolysis). ATP is also made during glycolysis. Two molecules of ATP are produced from each molecule of glucose.
Yeasts in bread dough also use alcoholic fermentation for energy. They produce carbon dioxide gas as a waste product. The carbon dioxide released causes bubbles in the dough and explains why the dough rises. Do you see the small holes in the bread pictured to the right? The holes were formed by bubbles of carbon dioxide gas.
As you have probably guessed, yeast is also used in producing alcoholic beverages. When making beer, brewers will add yeast to a mix of barley and hops. In the absence of oxygen, yeast will carry out alcoholic fermentation in order to convert the glucose in the barley into energy, producing the alcohol content as well as the carbonation present in beer.
Lactic Acid Fermentation
Lactic acid fermentation is carried out by certain bacteria, including the bacteria in yogurt. It is also carried out by your muscle cells when you work them hard and fast. This is how the muscles of the sprinters pictured above get energy for their short-lived — but intense — activity. When this happens, your muscles are using ATP faster than your cardiovascular system can deliver oxygen! The process by which this happens is summarized in the diagram below. Again, the two pyruvic acid molecules shown in the diagram come from the splitting of glucose in the first stage of the process (glycolysis). It is also during this stage that two ATP molecules are produced. The rest of the processes produce lactic acid. Note that, unlike in alcoholic fermentation, there is no carbon dioxide waste product in lactic acid fermentation.
Lactic acid fermentation produces lactic acid and NAD+. The NAD+ cycles back to allow glycolysis to continue so more ATP is made. Each circle represents a carbon atom.
Did you ever run a race, lift heavy weights, or participate in some other intense activity and notice that your muscles start to feel a burning sensation? This may occur when your muscle cells use lactic acid fermentation to provide ATP for energy. The buildup of lactic acid in the muscles causes a burning feeling. This painful sensation is useful if it gets you to stop overworking your muscles and allow them a recovery period, during which cells can eliminate the lactic acid.
Pros and Cons of Anaerobic Respiration
With oxygen, organisms can use aerobic cellular respiration to produce up to 38 molecules of ATP from just one molecule of glucose. Without oxygen, organisms must use anaerobic respiration to produce ATP, and this process produces only two molecules of ATP per molecule of glucose. Although anaerobic respiration produces less ATP, it has the advantage of doing so very quickly. For example, it allows your muscles to get the energy they need for short bursts of intense activity. Aerobic cellular respiration, in contrast, produces ATP more slowly.
Fermentation in Food Production
Anaerobic respiration is also used in the food industry. You read about yeast’s role in making bread and beer, but did you know that there are many microbes that are used to create the food we eat, including cheese, sour cream, yogurt, soy sauce, olives, pepperoni, and many more. Watch the video below to learn more about fermentation in the food industry.
The beneficial bacteria that make delicious food – Erez Garty, TED-Ed, 2016.
4.11 Cultural Connection
Fishing has always been part of the culture and nutrition of Indigenous peoples living on the west coast of Canada. Fish provides delicious important nutrients such as protein, Omega-3 fatty acids, calcium, iron, and Vitamins A, B, C and D. Traditionally, no part of the fish was wasted, including head, eyes, internal organs, and eggs.
Eulachon, also known as candle fish or oolichan, (pictured below) have been prized for their oil for thousands of years. The pathways of these fish dictated “grease trails” and are found from Bristol Bay, Alaska, all the way south to the Klamath River, California. Within BC, the areas of Nass, Knights Inlet, and Bella Coola had large trading centres for this important natural resource.
Photos by Brodie Guy – www.brodieguy.com CC BY-NC-ND 4.0
Euchalon were and are eaten fresh, smoked or dried, and as grease. The grease remains a highly valued food to Indigenous coastal communities. The flavour of the grease varies greatly depending not only on where the fish is from and how it is made, but also how long it is left to ferment. To ferment the eulachon, fish are left in a wood-lined locker dug into the soil for 10 days. Fermentation uses the action of fungi and bacteria to break down the fish making oil extraction much faster and easier.
To learn more, visit the First Nations Health Authority Traditional Foods Fact Sheet and a feature in the Yukon News, “Eulachon, oolicahn, hooligan: A fish by any other name is just as oily.”
4.11 Summary
- The cells of most living things produce ATP from glucose by aerobic cellular respiration, which uses oxygen. Some organisms instead produce ATP from glucose by anaerobic respiration, which does not require oxygen.
- An important way of making ATP without oxygen is fermentation. There are two types of fermentation: alcoholic fermentation and lactic acid fermentation. Both start with glycolysis, the first (anaerobic) stage of cellular respiration, in which two molecules of ATP are produced from one molecule of glucose.
- Alcoholic fermentation is carried out by single-celled organisms, including yeasts and some bacteria. We use alcoholic fermentation in these organisms to make biofuels, bread, and wine.
- Lactic acid fermentation is undertaken by certain bacteria, including the bacteria in yogurt, and also by our muscle cells when they are worked hard and fast.
- Anaerobic respiration produces far less ATP than does aerobic cellular respiration, but it has the advantage of being much faster. For example, it allows muscles to get the energy they need for short bursts of intense activity.
4.11 Review Questions
- Explain the primary difference between aerobic cellular respiration and anaerobic respiration.
- What is fermentation?
- Compare and contrast alcoholic and lactic acid fermentation.
- Identify the major pros and the major cons of anaerobic respiration relative to aerobic cellular respiration.
- What process is shared between aerobic cellular respiration and anaerobic respiration? Describe the process briefly. Why can this process happen in anaerobic respiration, as well as aerobic respiration?
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- What is the reactant (or starting material)common to aerobic respiration and both types of fermentation?
4.11 Explore More
Anaerobic Respiration, Bozeman Science, 2013.
Fermentation, The Amoeba Sisters, 2018.
Science of Beer: Tapping the Power of Brewer’s Yeast, KQED Science, 2014.
Attributions
Figure 4.11.1
Sprinters by Jonathan Chng on Unsplash is used under the Unsplash License (https://unsplash.com/license).
Figure 4.11.2
Alcoholic fermentation by Hana Zavadska/ CK-12 Foundation is used under a CC BY-NC 3.0 (https://creativecommons.org/licenses/by-nc/3.0/) license.
Figure 4.11.3
Bread [photo] by Orlova Maria on Unsplash is used under the Unsplash License (https://unsplash.com/license).
Figure 4.11.4
Lactic Acid Fermenation by Hana Zavadska/ CK-12 Foundation is used under a CC BY-NC 3.0 (https://creativecommons.org/licenses/by-nc/3.0/) license.
References
Bozeman Science. (2013, May 2). Anaerobic respiration. YouTube. https://www.youtube.com/watch?v=cDC29iBxb3w&feature=youtu.be
Hana Zavadska/CK-12 Foundation. (2016, August 15). Figure 2: Alcoholic fermentation [digital image]. In Brainard, J., and Henderson, R., CK-12’s College Human Biology FlexBook® (Section 4.11). CK-12 Foundation. https://www.ck12.org/book/ck-12-college-human-biology/section/4.11/
Hana Zavadska/CK-12 Foundation. (2016, August 15). Figure 4: Lactic acid fermentation [digital image]. In Brainard, J., and Henderson, R., CK-12’s College Human Biology FlexBook® (Section 4.11). CK-12 Foundation. https://www.ck12.org/book/ck-12-college-human-biology/section/4.11/
First Nations Health Authority. (2019, September 6). First Nations traditional foods facts Sheet [pdf]. https://www.fnha.ca/Documents/Traditional_Food_Fact_Sheets.pdf
Genest, M. (2017, May 24). Eulachon, oolichan, hooligan: A fish by any other name is just as oily [online article]. YukonNews.com. https://www.yukon-news.com/business/eulachon-oolichan-hooligan-a-fish-by-any-other-name-is-just-as-oily/
KQED Science. (2014, February 11). Science of beer: Tapping the power of brewer’s yeast. YouTube. https://www.youtube.com/watch?v=TVtqwWGguFk&feature=youtu.be
TED-Ed. (2016). The beneficial bacteria that make delicious food – Erez Garty. YouTube. https://www.youtube.com/watch?v=eksagPy5tmQ&feature=youtu.be
The Amoeba Sisters. (2018, April 30). Fermentation. YouTube. https://www.youtube.com/watch?v=YbdkbCU20_M&feature=youtu.be
Wikipedia contributors. (2020, June 21). Ethanol fuel. In Wikipedia. https://en.wikipedia.org/w/index.php?title=Ethanol_fuel&oldid=963675942
A complex organic chemical that provides energy to drive many processes in living cells, e.g. muscle contraction, nerve impulse propagation, and chemical synthesis. Found in all forms of life, ATP is often referred to as the "molecular unit of currency" of intracellular energy transfer.
Glucose (also called dextrose) is a simple sugar with the molecular formula C6H12O6. Glucose is the most abundant monosaccharide, a subcategory of carbohydrates. Glucose is mainly made by plants and most algae during photosynthesis from water and carbon dioxide, using energy from sunlight.
A set of metabolic reactions and processes that take place in the cells of organisms to convert biochemical energy from nutrients into adenosine triphosphate (ATP).
The metabolic pathway that converts glucose C₆H₁₂O₆, into pyruvate. The free energy released in this process is used to form the high-energy molecules ATP and NADH. Glycolysis is a sequence of ten enzyme-catalyzed reactions.
A series of chemical reactions used by all aerobic organisms to release stored energy through the oxidation of acetyl-CoA derived from carbohydrates, fats, and proteins.
A series of electron transporters embedded in the inner mitochondrial membrane that shuttles electrons from NADH and FADH2 to molecular oxygen. In the process, protons are pumped from the mitochondrial matrix to the intermembrane space, and oxygen is reduced to form water.
Relating to, involving, or requiring free oxygen.
Carried out in or pertaining to the absence of oxygen.
Respiration using electron acceptors other than molecular oxygen. Although oxygen is not the final electron acceptor, the process still uses a respiratory electron transport chain.
A metabolic process that produces chemical changes in organic substrates through the action of enzymes. In biochemistry, it is narrowly defined as the extraction of energy from carbohydrates in the absence of oxygen.
A biological process which converts sugars such as glucose, fructose, and sucrose into cellular energy, producing ethanol and carbon dioxide as by-products.
A metabolic process by which glucose and other six-carbon sugars are converted into cellular energy and the metabolite lactate, which is lactic acid in solution.
A fuel that is produced through contemporary processes from biomass, rather than a fuel produced by the very slow geological processes involved in the formation of fossil fuels, such as oil.
A large, dome-shaped muscle below the lungs that allows breathing to occur when it alternately contracts and relaxes.
