thylakoidokban
Thylakoidokban is a hypothetical organelle within plant cells that has been proposed in some theoretical models of cellular evolution. It is not a currently recognized or observed cellular structure. The concept of thylakoidokban is based on the idea of a specialized compartment for the light-dependent reactions of photosynthesis, potentially existing before the full development of chloroplasts as we know them today. It is imagined as a membrane-bound sac or stack of sacs, akin to thylakoids, but perhaps less integrated or complex than the grana and stroma lamellae found in mature chloroplasts. The prefix "thylakoid" refers to the flattened sacs within chloroplasts where chlorophyll is located and the light reactions of photosynthesis occur. The suffix "-okban" is not a standard biological term but is used here to denote a distinct, enclosed unit or sac. While speculative, the thylakoidokban concept serves as a thought experiment for understanding the evolutionary pathway leading to the sophisticated chloroplasts that carry out photosynthesis in modern plants. Research into the origins of chloroplasts continues to explore potential intermediate stages and ancestral organelles.