Biology Regents Practice Exam

A chloroplast is an organelle found in plant cells that plays a crucial role in the process of photosynthesis. It contains pigments, primarily chlorophyll, which absorb light energy, typically from the sun. This light energy is then converted into chemical energy in the form of glucose, which plants use as food.

Chloroplasts have a double membrane structure and contain their own DNA, allowing them to replicate independently within the cell. This unique feature supports the endosymbiotic theory, which suggests that chloroplasts and mitochondria were once free-living prokaryotic organisms that became integrated into eukaryotic cells.

The process of photosynthesis that occurs in chloroplasts not only supports the energy needs of the plant but also produces oxygen as a byproduct, which is essential for life on Earth. This central function of chloroplasts makes them vital for plant health and survival, as well as for the ecological balance of our planet.