21. Which product of glycolysis diffuses through the mitochondrial membranes to provide the fuel for the citric acid cycle?

22. Can all of the intermediates of glycolysis penetrate through the mitochondrial membranes? Why would this be a disadvantage, if it were so?

23. How does the NADH produced in glycolysis arrive at the site of the respiratory chain inside a mitochondrion, if the mitochondrial membrane is impermeable to NADH?

24. To what extent do mitochondria have their own genetic apparatus, and what proteins do they make?

25. What are thylakoids and grana in green-plant chloroplasts?

26. Where do the light and dark reactions of photosynthesis take place relative to these thylakoids and grana?