Final answer:
The structure that allows autotrophs to carry out photosynthesis is the chloroplast.
Step-by-step explanation:
The structure that is absent in heterotrophs but present in autotrophs that allows them to carry out photosynthesis is the chloroplast. Chloroplasts contain the pigment chlorophyll, which captures light energy and converts it into chemical energy through photosynthesis.
Learn more about Autotrophs and photosynthesis