What are similarities between mitochondria and chloroplasts?

• A. Both create internal proton gradients by electron transport and have a double membrane system.
• B. Both perform photosynthesis.
• C. Both lack their own DNA.
• D. Both are found only in plant cells.

Answer: (B)

Both organelles generate ATP by using a proton gradient across a membrane, and both have a double-membrane envelope. In mitochondria, the electron transport chain pumps protons across the inner membrane into the intermembrane space, creating a gradient that drives ATP synthesis as protons flow back through ATP synthase. In chloroplasts, light-driven electron transport pumps protons across the thylakoid membrane into the lumen, and those protons power ATP production in the stroma for carbon fixation. The shared feature is this proton-motive force for ATP creation, not that both perform photosynthesis—that task is unique to chloroplasts. Also, note that both organelles contain their own DNA and ribosomes, and mitochondria are present in many eukaryotic cells, not just plants.