Stroma is to the thylakoid interior in chloroplasts as is to in mitochondria.

Stroma is to the thylakoid iterior in chloroplasts as intermembrane space is to matrix in mitochondria. The intermembrane space (IMS) is the region between the inner membrane and the outer membrane of a mitochondrion. It tends to have a low pH because of the proton gradient which results when protons are pumped from the mitochondrial matrix into the intermembrane space during electron transport.