Glossary
mitochondria
Mitochondria are the cell structures that release the energy stored in food, which is why they are called the cell's powerhouses; a hard-working cell like a muscle cell is packed with them.
Mitochondria are the structures inside a cell that release the energy from food — the cell's powerhouses. They take glucose and oxygen and produce the energy the cell can use, giving off carbon dioxide and water as they do. That reaction is cellular respiration, which is the reverse of photosynthesis.
Shape follows the job. A cell that works hard needs more energy, so it carries more mitochondria: a muscle cell is dense with them, while a fat-storage cell is not. That is the usual question — when a stem asks which cell contains the most mitochondria, the answer is the cell doing the most work.
The other cell parts are easy to swap with it, and the subtest does swap them. The nucleus holds the DNA and directs the cell's activities; ribosomes build proteins; the membrane surrounds the cell; the cytoplasm is the fluid the parts sit in; a plant cell also has a rigid cell wall. Mitochondria are never the control center of the cell — the nucleus is, and that is the line the questions test.
Taught in
Related terms
- photosynthesis — Photosynthesis is how a plant uses light energy to turn carbon dioxide and water into sugar, releasing oxygen; respiration runs the reaction the other way.
- cell membrane — The cell membrane is the thin outer boundary of a cell. It holds the cell together and controls what passes in and out; plant cells also have a rigid cell wall outside it.
Source: Official ASVAB — subtest descriptions (what each subtest asks) and the CAT-ASVAB scored-question counts (accessed 2026-09)