In the preceding section, you saw how chemiosmosis works in one type of prokaryotic cell. As you'll see in this topic, the same components, electron transport chain and ATP synthase, are found in mitochondria and chloroplasts. And as in the prokaryotic example, chemiosmosis in both organelles involves harvesting energy from redox reactions, storing the energy in a proton gradient, and producing ATP.

You might consider the functions of these organelles the reverse of one another - after all, the mitochondrion degrades nutrient molecules, while the chloroplast synthesizes them. But the process of chemiosmosis involved in each is similar. You'll see that differences in the arrangement of components and energy inputs/outputs lead to different outcomes of chemiosmosis in the two organelles.

What you'll learn in this topic

For both mitochondrion and chloroplast:

• the membranes where chemiosmosis occurs
• which electron acceptors and donors are involved
• how chemiosmosis connects metabolic pathways in the organelle and in the rest of the cell

Your task is to construct working models of chemiosmosis in the mitochondrion and chloroplast. Notice the similarities and differences between them.