Cellular Respiration
What Are the Differences between Aerobic and Anaerobic Respiration?
Aerobic Versus Anaerobic Respiration
Aerobic respiration refers to the production of ATP using oxygen as a final electron acceptor in the electron transport chainglossary term (opens in a new window). Aerobes are organisms that obtain oxygen or absorb oxygen from their environments. These organisms typically produce ATP using aerobic respirationglossary term (opens in a new window).
Some organisms live in oxygen-poor environments or experience circumstances of low oxygen. They would not survive if they required oxygen to produce ATP. Many of these organisms undergo a process similar to aerobic respiration, but they use a different molecule as the final electron acceptor. The process is called anaerobic respirationglossary term (opens in a new window). Examples of alternative final electron acceptors are sulfate (SO42-), nitrate (NO3-), and sulfur (S).
Teacher Note: Misconception
Students may believe that fermentation only takes place in bacteria and yeast. In fact, even human muscle cells use fermentation in low-oxygen conditions.
Cells can obtain energy from food without the use of oxygen or an electron transport chain. Fermentationglossary term (opens in a new window) is an anaerobic process by which cells ensure that glycolysisglossary term (opens in a new window) takes place repeatedly to generate as much ATP as possible. Fermentation involves the conversion of pyruvate to another molecule. Pyruvate may be converted to lactate or ethanol. During these reactions, the NADH produced by glycolysis is oxidized back to NAD+. By ensuring a steady supply of NAD+, a cell can continue to undergo glycolysis uninterrupted.
Teacher Note: Practice
In this activity, students analyze data from an investigation of yeast fermentation by making qualitative and quantitative measures and graphing their results to make valid and reliable claims about cellular respiration. In the analysis and conclusion at the end of the lab, students consider the limitations of their data analysis and suggest ways in which they could collect more accurate data. If time permits, students can redo the investigation using the improved data collection methods they suggest and revise their conclusions in light of the new data.
Fermentation is very useful in cases where oxygen is in short supply. However, with only the small ATP yield from glycolysis, it is a much less efficient way to metabolize food than aerobic cellular respirationglossary term (opens in a new window).
Teacher Note: Practice
In the Hands-On Activity that follows, students plan an investigation collaboratively to produce data to serve as the basis for evidence to support explanations of aerobic and anaerobic respiration. Students perform two investigations, manipulating a variable in the second investigation, and graph the data they collect. To extend this activity, instruct groups to design and, if time permits, conduct a third investigation in which they manipulate the variable again. Students can then revise or expand their explanations based on the new data they gather.
Teacher Note: Practice
Students apply scientific ideas and evidence to provide an explanation of sauerkraut creation and the relationship between cellular respiration and the amount of oxygen available to cells. To extend this item, assign students a food that requires fermentation to prepare (or allow them to choose one) and instruct them to create a poster or presentation explaining the processes by which the food is created. Students should cite evidence for the chemical reactions that enable the creation of the food.
