Final answer:
To recognize a chloroplast in an electron micrograph, look for a flat disc shape with an inner and outer membrane, as well as internal stacks called thylakoids that contain chlorophyll and are organized into grana.
Step-by-step explanation:
To recognize an electron micrograph of a chloroplast, you should look for a structure with an inner and outer phospholipid membrane, an internal fluid called the stroma, and stacks of thylakoids. Chloroplasts typically have a flat disc shape, usually measuring 2 to 10 micrometers in diameter and about 1 micrometer thick. The thylakoids, containing green chlorophyll molecules, are arranged in stacks known as grana, and these are where photosynthesis takes place. In electron micrographs, you can often see the thylakoids as stacks or grana.
A chloroplast might also show small circles of DNA, ribosomes within the stroma, and starch grains especially in micrographs where the chloroplast is active in photosynthesis. In Transmission Electron Micrographs (TEM), the detail will be higher, and you may also observe the intermembrane space and the thylakoid space or lumen. Look for images with clear labeling that might indicate 'T-thylakoids' and 'Cp' for chloroplasts when trying to identify chloroplast structures.