Summary
The green plant organelle containing chlorophyll where light energy is converted to chemical energy in photosynthesis.
In depth
Chloroplasts have a double envelope, an inner stroma and stacks of thylakoids called grana that hold chlorophyll and electron carriers. Light reactions occur in the thylakoid membranes, and the Calvin cycle in the stroma.
Like mitochondria they contain circular DNA and 70S ribosomes, supporting the endosymbiotic origin. They also make fatty acids, amino acids and store starch grains.
Chloroplasts belong to the plastid family, which also includes chromoplasts (pigments in fruit and flowers), leucoplasts and amyloplasts (starch storage). A leaf mesophyll cell can contain 50 to 100 chloroplasts, each about 5 micrometres long. Starch grains and lipid droplets called plastoglobuli store products and pigments.
Chloroplasts divide by fission, move within the cell toward or away from light, and exchange signals with the nucleus to coordinate gene expression, since most chloroplast proteins are made from nuclear genes and imported.
Frequently asked questions
What is Chloroplast?
The green plant organelle containing chlorophyll where light energy is converted to chemical energy in photosynthesis.
Which area of biology covers Chloroplast, and how advanced is it?
Chloroplast is one of the 52 topics in Cell Biology. It is rated Beginner, so it suits learners who are starting out in biology. Related topics in this area include Prokaryotic Cell, Endosymbiotic Theory, Mitochondrion.
Why does Chloroplast matter?
Chloroplasts are the entry point of nearly all the energy in food chains.
Can you give an example of Chloroplast?
In strong light chloroplasts line up along the cell walls parallel to the light to avoid damage, and in dim light they spread across the face to capture more.
What should I learn before Chloroplast?
Chloroplast is a Beginner topic, so no earlier topic is required. Other Beginner topics in Cell Biology that pair well with it include Cell Theory, Prokaryotic Cell, Eukaryotic Cell.
What topics are related to Chloroplast?
The closest topics to Chloroplast are Prokaryotic Cell, Endosymbiotic Theory, Mitochondrion, Cytoplasm. Comparing them side by side is a good way to see how the ideas connect.
How can I check that I understand Chloroplast?
Read the summary and the in-depth section, then use the quick check on the interactive lesson for Chloroplast. To practise the whole of Cell Biology, use the Cell Biology quiz.
How is Chloroplast different from Prokaryotic Cell?
Chloroplast: The green plant organelle containing chlorophyll where light energy is converted to chemical energy in photosynthesis. Prokaryotic Cell: A simple cell with no membrane-bound nucleus; its DNA lies in a nucleoid region, as in bacteria and archaea. Read both side by side and note what each one explains.
How should I study Chloroplast step by step?
First, read the summary and write the definition in your own words. Second, read the in-depth section and note any example. Third, compare it with Prokaryotic Cell and explain the difference aloud. Finally, take the Cell Biology quiz and come back to this page for any question you miss.