What does chloroplast mean?
A chloroplast is a specialized organelle found in the cells of plants and algae, distinguished by its green pigment, chlorophyll. Its essential role is to carry out photosynthesis: absorbing sunlight and using that energy to convert carbon dioxide and water into glucose and oxygen. This process underpins virtually every food chain on Earth, making the chloroplast one of the most biologically consequential structures known. Under a microscope, chloroplasts appear as small, disc-shaped bodies suspended within the cell's cytoplasm, often dozens to hundreds per cell. Beyond their immediate function, they are scientifically fascinating because they carry their own DNA, evidence that they evolved from free-living cyanobacteria that were absorbed by ancestral cells billions of years ago — a phenomenon called endosymbiosis. The term appears chiefly in biology education and research writing, and understanding it opens a door to grasping how life on our planet is powered.
nounA chloroplast is a plastid in plant and algal cells that contains the green pigment chlorophyll, where photosynthesis takes place. It converts light energy into chemical energy stored as sugars.
- A chlorophyll-containing organelle in plant cells responsible for photosynthesis
"Chloroplasts capture sunlight and convert it into the sugars that fuel nearly all life on Earth."
"The leaf cells contained numerous green chloroplasts visible under low magnification."
"Scientists traced the evolutionary origins of the chloroplast to an ancient cyanobacterium engulfed by a eukaryotic cell."
Standard regular plural; used when referring to more than one of these organelles.
"Each mesophyll cell may contain fifty or more chloroplasts."
Every bite of food you've ever eaten traces its energy back to a tiny green organelle smaller than the width of a human hair.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of chloroplast
The word 'chloroplast' derives from Greek roots: 'chloros' meaning green and 'plastos' meaning formed or molded. It entered English in the late nineteenth century as scientists began systematically describing cellular structures. It shares these roots with related terms such as 'chlorophyll' (green pigment) and 'chlorine' (the pale-green gas).
How chloroplast is actually used
Primarily used in scientific, academic, and educational contexts; rare in everyday conversation. Plural is 'chloroplasts'.
Easily confused with chloroplast
A chloroplast performs photosynthesis using light, while a mitochondrion generates energy by breaking down sugars through cellular respiration.