Write short notes on mitochondrion and chloroplast.

Mitochondria are double-membrane-bound organelles known as the "powerhouses of the cell" because they generate most of the cell's ATP (adenosine triphosphate) through cellular respiration. The outer membrane is smooth, while the inner membrane is highly folded into cristae, providing extensive surface area for ATP production. The inner compartment, called the matrix, contains enzymes for the Krebs cycle, mitochondrial DNA, and ribosomes, enabling mitochondria to produce some of their own proteins. Present in all eukaryotic cells (both plant and animal), mitochondria convert the chemical energy stored in glucose and other nutrients into ATP through oxidative phosphorylation, making this energy available for cellular work like muscle contraction, protein synthesis, and active transport.

Chloroplasts are specialized organelles found only in plant cells and some protists, responsible for photosynthesis—the process of converting light energy into chemical energy stored in glucose. Like mitochondria, they have a double membrane structure, but additionally contain an internal membrane system of flattened sacs called thylakoids, stacked into structures called grana, where light-dependent reactions occur. The fluid surrounding the thylakoids, called stroma, contains enzymes for light-independent reactions (Calvin cycle), along with chloroplast DNA and ribosomes. The green pigment chlorophyll, embedded in thylakoid membranes, captures light energy and gives plants their characteristic green color. Chloroplasts transform carbon dioxide and water into glucose and oxygen using sunlight, essentially fueling most life on Earth by producing the organic compounds and oxygen that other organisms depend upon.