Anaerobic respiration occurs without oxygen by fermentation. There are two types of fermentation: lactic acid fermentation and alcoholic fermentation. Anaerobic respiration produces less ATP than aerobic respiration, but anaerobic respiration occurs more quickly.
- Define fermentation.
- Describe lactic acid fermentation and alcoholic fermentation.
- Compare the advantages of aerobic and anaerobic respiration.
alcoholic fermentation: type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to ethanol and carbon dioxide and the formation of NAD+
fermentation: type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to one or more other compounds and the formation of NAD+
lactic acid fermentation: type of anaerobic respiration that includes glycolysis followed by the conversion of pyruvic acid to lactic acid and the formation of NAD+
Check Your Understanding
Take a poll of your students. This poll is not meant to be scientific, but is meant to stimulate thinking about the lesson content.
- The first question for your students is: “Do you think more high school students are better at sprinting or at distance running?” Tally the opinions and write on the blackboard. Next, ask them if they are better at sprinting or at running longer distances. (Obviously, if there are physically impaired students in your class, you will modify this poll.) Tally the results. As a class, calculate the percent of students in each category. Were the actual results the same as the predicted ones?
- After your students have completed this activity, tell them that you will be teaching them about aerobic and anaerobic respiration, and that different types of muscles fibers are specialized for one or the other. Some people have more “sprinting fibers,” which are specialized for anaerobic metabolisms and others, more “endurance” fibers, which are specialized for aerobic respiration. Specific training can alter the distribution between the two types. For example, there will be an increase in endurance fibers (also known as slow-twitch) in a person training for a marathon.
Reference: Ingalls, Christopher. 2004. Nature vs. nuture: can exercise really alter fiber type composition in human skeletal muscle? J. Appl Physiol 97: 1591-1592. http://jap.physiology.org/cgi/content/full/97/5/1591
Introducing the Lesson
Ask students to recall from Lesson 4.3 which stage of aerobic respiration does not require oxygen (glycolysis). State that anaerobic respiration also starts with glycolysis. Tell the class they will read about other stages of anaerobic respiration in this lesson.
You can demonstrate lactic acid fermentation by making yogurt in the classroom. You can find instructions at the URL below. It takes several days for the yogurt cultures to finish growing. You can also demonstrate alcoholic fermentation by letting yeast dough rise in the classroom (following package directions). This can be done in one class period. Make sure students do not taste the demonstrations. Discuss how the two processes are similar.
Give visual and kinesthetic learners a chance to see, smell, and taste fermented foods from a variety of ethnic cuisines (e.g., sauerkraut, pickles, miso, soy sauce, cider, cheese, yogurt, pepperoni). Explain that all the foods have been broken down by anaerobic respiration in microbes.
Instruct a small group of students to create a board game that correctly models the process of lactic acid or alcoholic fermentation. Have them demonstrate their game to the class and explain how it models the biological process.
Ask the class to infer what signs they would look for as evidence of lactic acid fermentation and alcoholic fermentation. (Sample answers: sour taste for lactic acid fermentation; gas bubbles for alcoholic fermentation)
Tell students that sprinters have more muscle fibers specialized for lactic acid fermentation than endurance runners. This gives sprinters a burst of energy, but it doesn’t last long. It also causes lactic acid to build up in their muscles, and this must be metabolized by the liver. You or your students can learn more at the URL below.
Reinforce and Review
Copy and distribute the lesson worksheets in the CK-12 Biology Workbook. Ask students to complete the worksheets alone or in pairs as a review of lesson content.
Have students answer the Review Questions listed at the end of the lesson in the FlexBook®.
Points to Consider
Two important functions of cells are making food and using it for energy. Photosynthesis and cellular respiration are the processes that carry out these functions. Other important functions of cells are growing and dividing.
- Do you know how cells grow? What do you think controls the growth of cells?
- How do you think cells divide? Do all cells divide in the same way?