BiochemistryLesson 3 of 5 in the course How Cells Obtain Energy

Citric Acid Cycle Products and Oxidative Phosphorylation

5 flashcards · 5 quiz questions · 5 match pairs · 4 fill-in sentences · English

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Summary

The citric acid cycle is a central stage of aerobic cellular respiration. It processes the acetyl groups derived from pyruvate, captures energy in electron carriers, and releases carbon dioxide. Understanding its cyclic structure and products helps explain how cells prepare energy for ATP production later in respiration.

When oxygen is available, pyruvate made during glycolysis enters the mitochondrion in eukaryotic cells. In the mitochondrial matrix, pyruvate is transformed: one carbon is removed as carbon dioxide, and the remaining two-carbon acetyl group attaches to coenzyme A (CoA). CoA is made from vitamin B5. The resulting molecule is acetyl CoA.

All flashcards

What is acetyl CoA?
A molecule in which coenzyme A carries a two-carbon acetyl group into the citric acid cycle.
What makes the citric acid cycle regenerative?
Its final reactions restore the acceptor molecule that combines with an incoming acetyl group.
What does one turn of the citric acid cycle produce?
Three NADH, one FADH2, one ATP or equivalent, and two CO2.
What is chemiosmosis?
The movement of hydrogen ions through ATP synthase, coupled to ATP production.
How can the citric acid cycle support biosynthesis?
Some cycle intermediates can be used to build molecules such as non-essential amino acids.

Quiz questions

  1. At the end of the mitochondrial electron transport chain, what role does oxygen play?Answer: It accepts electrons at complex IV and combines with hydrogen ions to form water.
  2. During mitochondrial electron transport, where are hydrogen ions pumped from and to?Answer: From the matrix into the intermembrane space
  3. Which process is called chemiosmosis?Answer: Hydrogen ions flowing through ATP synthase as ATP is produced
  4. Why can the shuttle used to transfer glycolytic electrons affect ATP yield?Answer: FAD-based entry yields fewer ATP molecules than NAD-based entry.
  5. Mutations in which genetic material can cause mitochondrial diseases?Answer: Nuclear DNA or mitochondrial DNA

Based on Concepts of Biology by Samantha Fowler, Rebecca Roush, James Wise (OpenStax), licensed CC BY 4.0. Adapted into a summary, flashcards and quizzes.

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