A model of the photosynthetic membrane from higher plants is presented. The different photosystems, PSIα, PSIβ, PSIIα and PSIIβ, are located in separate domains. The photosystems with the largest antenna systems, the alpha systems, are in the grana and the other in the stroma lamellae. In each grana disc PSIα is located in a flat annulus surrounding a circular PSIIα domain. In this the PSIIα units with the largest antennae are found in the center. The model is consistent with results from recent membrane fractionation experiments.
