Lactic Acid Fermentation: Recycling Energy in the Absence of Oxygen

Biology Grades High School 11:21 Video
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Lesson Description

This lesson explores lactic acid fermentation, an anaerobic process that allows cells to continue producing ATP through glycolysis when oxygen is limited. We'll examine the process, its importance, and examples of its use in food production.

Video Resource

Lactic acid fermentation | Cellular respiration | Biology | Khan Academy

Khan Academy

Duration: 11:21
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Key Concepts

  • Glycolysis
  • Lactic acid fermentation
  • Oxidation and reduction (redox) reactions
  • NAD+/NADH cycle
  • Anaerobic respiration

Learning Objectives

  • Describe the process of lactic acid fermentation and its role in recycling NAD+.
  • Explain why lactic acid fermentation is necessary in the absence of oxygen.
  • Identify examples of lactic acid fermentation in food production.
  • Differentiate between cellular respiration and lactic acid fermentation.
  • Explain how the NADH is oxidized and the pyruvic acid or pyruvate is reduced.

Educator Instructions

  • Introduction (5 mins)
    Begin by reviewing the basics of glycolysis and cellular respiration. Briefly discuss the importance of oxygen in the electron transport chain. Introduce the concept of fermentation as an alternative pathway when oxygen is limited.
  • Video Viewing (15 mins)
    Play the Khan Academy video on lactic acid fermentation. Encourage students to take notes on the key steps and concepts presented in the video. Pause at key points to clarify any confusion.
  • Discussion and Explanation (15 mins)
    Lead a class discussion to reinforce the concepts from the video. Focus on the following points: * The role of NAD+ and NADH in glycolysis and fermentation. * The purpose of lactic acid fermentation: recycling NAD+ for glycolysis to continue. * The chemical equation for lactic acid fermentation (pyruvate + NADH -> lactate + NAD+). * Examples of lactic acid fermentation in food production (yogurt, kimchi, sauerkraut). * The difference between pyruvic acid and pyruvate as well as lactic acid and lactate.
  • Application and Examples (10 mins)
    Discuss other real-world examples of lactic acid fermentation, such as in muscle cells during intense exercise. Have students brainstorm other possible applications of this process.

Interactive Exercises

  • Process Mapping
    Students create a flow chart illustrating the steps of lactic acid fermentation, including the reactants, products, and enzymes involved. They should note what gets oxidized and reduced.
  • Food Fermentation Research
    Students research different types of fermented foods and present their findings to the class, focusing on the microorganisms involved and the chemical changes that occur during fermentation.

Discussion Questions

  • Why is lactic acid fermentation important for cells in the absence of oxygen?
  • How does lactic acid fermentation differ from cellular respiration in terms of ATP production?
  • What are some of the benefits and drawbacks of lactic acid fermentation?
  • How does the Lactobacillus bacteria contribute to making yogurt, kimchi, and sauerkraut?

Skills Developed

  • Critical thinking
  • Scientific reasoning
  • Information synthesis
  • Process analysis
  • Visual Representation

Multiple Choice Questions

Question 1:

What is the primary purpose of lactic acid fermentation?

Correct Answer: To recycle NAD+ so glycolysis can continue

Question 2:

In lactic acid fermentation, pyruvate is converted into what?

Correct Answer: Lactic acid

Question 3:

Which of the following organisms is commonly used in lactic acid fermentation for food production?

Correct Answer: Lactobacillus

Question 4:

Which process is performed before Lactic Acid Fermentation?

Correct Answer: Glycolysis

Question 5:

What is NADH oxidized into during lactic acid fermentation?

Correct Answer: NAD+

Question 6:

Lactic acid fermentation is an example of what type of respiration?

Correct Answer: Anaerobic

Question 7:

Kimchi and sauerkraut are produced through which process?

Correct Answer: Lactic acid fermentation

Question 8:

Where does lactic acid fermentation primarily occur in humans?

Correct Answer: Muscle cells

Question 9:

Which molecule accepts electrons from NADH during lactic acid fermentation?

Correct Answer: Pyruvate

Question 10:

What enzyme catalyzes the reduction of pyruvate to lactate?

Correct Answer: Lactic acid dehydrogenase

Fill in the Blank Questions

Question 1:

Lactic acid fermentation occurs in the absence of ________.

Correct Answer: oxygen

Question 2:

The main product of lactic acid fermentation is ________ acid.

Correct Answer: lactic

Question 3:

During lactic acid fermentation, NADH is ________ to NAD+.

Correct Answer: oxidized

Question 4:

The conjugate base of pyruvic acid is ________.

Correct Answer: pyruvate

Question 5:

________ is a type of bacteria used in the production of yogurt.

Correct Answer: Lactobacillus

Question 6:

The breakdown of glucose into pyruvate is called ________.

Correct Answer: glycolysis

Question 7:

Sauerkraut is made from fermented ________.

Correct Answer: cabbage

Question 8:

Lactic acid fermentation produces a net gain of ________ ATP molecules per glucose molecule.

Correct Answer: two

Question 9:

During intense exercise, muscle cells use lactic acid fermentation to regenerate ________.

Correct Answer: NAD+

Question 10:

Pyruvic acid or pyruvate accepts electrons from ________ during lactic acid fermentation.

Correct Answer: NADH

Educational Standards

B.LS1.7:Use a model to illustrate that cellular respiration is a chemical process whereby the bonds of food molecules and oxygen molecules are broken and the bonds in new compounds are formed, resulting in a net transfer of energy. B.LS2.3:Construct and revise an explanation based on evidence for the cycling of matter and the flow of energy in aerobic and anaerobic conditions.

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