Chloroplast
Organelle that conducts photosynthesis in plants and algae.
A chloroplast is a type of organelle known as a plastid that conducts photosynthesis mostly in plant and algal cells. Chloroplasts have a high concentration of chlorophyll pigments which capture energy from sunlight, convert it to chemical energy, and decompose water to release oxygen. The chemical energy is then used to make sugar and other organic molecules from carbon dioxide in the Calvin cycle. Chloroplasts also carry out fatty acid synthesis, amino acid synthesis, and immune response in plants.
- etymology
- Greek chloros (green) and plastes (the one who forms)
- origin
- Endosymbiotic from cyanobacteria, approximately two billion years ago
- key_feature
- Contains its own DNA separate from the cell nucleus
Lore & Background
The word chloroplast is derived from the Greek words chloros, meaning green, and plastes, meaning the one who forms. Chloroplasts are highly dynamic, circulating and moving within cells, and their behavior is strongly influenced by environmental factors such as light color and intensity.
Reader's Guide
Chloroplasts are central to photosynthesis, the process that sustains most life on Earth by converting sunlight into chemical energy. They are believed to have arisen from a single endosymbiotic event around two billion years ago, when a free-living cyanobacterium was engulfed by an early eukaryotic cell. Chloroplasts cannot be made anew by the plant cell and must be inherited during cell division. They contain their own DNA, separate from the cell nucleus, a remnant of their cyanobacterial ancestor. With one exception (the amoeboid Paulinella chromatophora), all chloroplasts can be traced back to that single endosymbiotic event. However, chloroplasts are found in extremely diverse organisms due to many secondary and even tertiary endosymbiotic events, where organisms engulfed other photosynthetic eukaryotes. This process has led to chloroplasts with additional membranes and has spread photosynthesis across many unrelated lineages.
Did You Know?
- Chloroplasts have a high concentration of chlorophyll pigments that capture energy from sunlight and decompose water to release oxygen.
- Chloroplasts cannot be made anew by the plant cell and must be inherited by each daughter cell during cell division.
- All primary chloroplasts belong to one of four lineages: glaucophyte, rhodophyte (red), chloroplastida (green), and the amoeboid Paulinella chromatophora.
- Secondary chloroplasts have additional membranes outside the original two in primary chloroplasts, resulting from secondary endosymbiosis.
Frequently Asked Questions
Who is Chloroplast?
Chloroplast is a membrane-bound organelle, specifically a type of plastid, residing in plant and algal cells. Its name blends the Greek words for 'green' and 'the one who forms,' a fitting title for the cell's green, shape-making energy engine.
What are Chloroplast's powers and role?
Chloroplast soaks up sunlight through dense chlorophyll pigments, splits water molecules to release oxygen, and channels the captured light energy into building sugars and other organic molecules from carbon dioxide via the Calvin cycle. Beyond photosynthesis, it also handles fatty acid synthesis, amino acid production, and immune signaling within the plant.
How does Chloroplast's story end?
When a chloroplast becomes damaged or the cell no longer needs photosynthesis, the organelle is broken down through autophagy and its components are recycled. The cell dismantles the structure and reuses the molecular building blocks for other metabolic tasks.
Why is Chloroplast so important?
Chloroplast is the reason Earth's atmosphere is rich in oxygen and the foundation of virtually every food chain on the planet. Without its ability to fix carbon dioxide into organic molecules, complex multicellular life simply could not exist.
Where did Chloroplast come from?
Chloroplast originated roughly two billion years ago when an ancestral eukaryotic cell engulfed a free-living cyanobacterium and retained it as a permanent internal partner. This endosymbiotic event explains why chloroplasts still carry their own circular DNA, entirely separate from the host cell's nucleus.
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