host cell chloroplast part host cell chloroplast thylakoid membrane cellular_component GO:0033654 Any sac-like membranous structures (cisternae) in a chloroplast found in host cells, combined into stacks (grana) and present singly in the stroma (stroma thylakoids or frets) as interconnections between grana. The host is defined as the larger of the organisms involved in a symbiotic interaction. host thylakoid membrane