Answer: Cristae.
- A Grana
- B Stroma
- C Cristae
- D Lumen
Correct answer: C. Cristae
Explanation: The inner mitochondrial membrane folds into cristae, greatly increasing surface area for ATP synthesis.
Animal cell structure with major organelles labeled. Image: LadyofHats (Mariana Ruiz), Public Domain, via Wikimedia Commons.
Concept context
Cell theory, prokaryotic vs eukaryotic cells, organelles and their functions. Foundation of all biology.