AP Biology Questions on Alternative Electron Acceptors in Anaerobic Respiration

📚 Quick Study Guide

• 🧪 Anaerobic respiration uses electron acceptors other than $O_2$.
• 🦠 Common alternative electron acceptors include: $NO_3^-$, $SO_4^{2-}$, $Fe^{3+}$, and organic molecules.
• 🌱 Denitrification: $NO_3^- \rightarrow N_2$ (occurs in some bacteria).
• 🔥 Sulfate reduction: $SO_4^{2-} \rightarrow H_2S$ (occurs in some bacteria and archaea).
• 🧱 Iron reduction: $Fe^{3+} \rightarrow Fe^{2+}$ (occurs in some bacteria and archaea).
• 💡 Methanogenesis: $CO_2 \rightarrow CH_4$ (occurs in some archaea).
• 📝 Each alternative electron acceptor yields a different amount of ATP compared to oxygen.

Practice Quiz

1. Which of the following is NOT an alternative electron acceptor used in anaerobic respiration?
   1. $NO_3^-$
   2. $SO_4^{2-}$
   3. $O_2$
   4. $Fe^{3+}$
2. In denitrification, which of the following conversions occurs?
   1. $N_2 \rightarrow NO_3^-$
   2. $NO_3^- \rightarrow N_2$
   3. $SO_4^{2-} \rightarrow H_2S$
   4. $CO_2 \rightarrow CH_4$
3. Which process uses sulfate as a terminal electron acceptor?
   1. Denitrification
   2. Methanogenesis
   3. Sulfate reduction
   4. Iron reduction
4. Which of the following organisms commonly performs methanogenesis?
   1. Bacteria
   2. Archaea
   3. Fungi
   4. Protists
5. What is the product of iron reduction?
   1. $Fe^{3+}$
   2. $Fe^{2+}$
   3. $H_2S$
   4. $CH_4$
6. Compared to aerobic respiration, anaerobic respiration typically yields:
   1. More ATP
   2. Less ATP
   3. The same amount of ATP
   4. Variable amounts of ATP depending on the organism
7. Which of the following processes is most likely to occur in an oxygen-depleted environment?
   1. Aerobic respiration
   2. Photosynthesis
   3. Anaerobic respiration
   4. Nitrogen fixation