On the structure of the spinach chloroplast

Abstract

The structure of spinach chloroplasts was investigated with the aid of the electron microscope. It has been established that:

1. 1. the outer membrane of the chloroplasts is composed of both proteins and lipoids.

2. 2. the stroma is also built up by these components.

3. 3. within the stroma membranes with surface design occur.

4. 4. a proteinaceous frame—which most probably is no artefact—occurs in the stroma. This framework strikingly resembles that found by 21 in the Tubifex egg.

5. 5. the grana are surrounded by a membrane composed of proteins and lipoids. Some evidence has been obtained that these substances occur as an outer lipoid layer and an inner proteinaceous layer.

6. 6. in agreement with the results of 9, the grana are furthermore composed of proteins discs and lipoids.

7. 7. grana showed one ring in electron diffraction diagrams corresponding with distances of about 2 A.