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Cell Structure

Mitochondria - Turning on the Powerhouse

Mitochondria are known as the powerhouses of the cell. They are organelles that act like a digestive system that takes in nutrients, breaks them down, and creates energy for the cell. The process of creating cell energy is known as cellular respiration. Most of the chemical reactions involved in cellular respiration happen in the mitochondria. A mitochondrion is shaped perfectly to maximize its efforts.

Mitochondria are very small organelles. You might find cells with several thousand mitochondria. The number depends on what the cell needs to do. If the purpose of the cell is to transmit nerve impulses, there will be fewer mitochondria than in a muscle cell that needs loads of energy. If the cell feels it is not getting enough energy to survive, more mitochondria can be created. Sometimes they can even grow, move, and combine with other mitochondria, depending on the cell's needs.

Mitochondria Structure

Mitochondria simple structure Mitochondria have two membranes (not one as in other organelles). The outer membrane covers the organelle and contains it. The inner membrane folds over many times (cristae). That folding increases the surface area inside the organelle. Many of the chemical reactions happen on the inner membrane of the mitochondria. The increased surface area allows the small organelle to do as much work as possible. If you have more room to work, you can get more work done. Similar surface area strategies are used by microvilli in your intestinal cells. The fluid inside of the mitochondria is called the matrix.

Using Oxygen to Release Energy

How are mitochondria used in cellular respiration? The matrix is filled with water (H2O) and proteins (enzymes). Those proteins take food molecules and combine them with oxygen (O2). The mitochondria are the only place in the cell where oxygen can be combined with the food molecules. After the oxygen is added, the material can be digested. They are working organelles that keep the cell full of energy.

A mitochondrion may also be involved in controlling the concentration of calcium (Ca) within the cell.

Next Stop On Biology4Kids Tour
Next Page on Cell Structure
- Overview
- Cell Membrane
- Membrane Proteins
- Cell Walls
- Connections
- Cytoplasm
- Nucleus
- Chromosomes
- Centrioles
- Ribosomes
> Mitochondria
- Chloroplasts
- Endo. Reticulum
- Golgi Complex
- Vacuoles
- Microfilaments
- Microtubules
- Lysosomes
- Peroxisomes


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Chalk Talk: Mitochondria (US-NSF Video)
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Cell Structure Quiz

Cell Mitochondria Quiz

Useful Reference Materials
Encyclopædia Britannica:
Books on
- Modern Biology (Rinehart and Holt)
- Campbell Biology (Campbell, Reece, Urrym Cain, and Wasserman)
- Campbell Biology: Concepts and Connections (Reese, Taylor, Simon, and Dickey)
- Prentice Hall: Biology (Miller and Levine)

- Biology4Kids: Phagocytosis
- Chem4Kids: Biochemistry
- Chem4Kids: Metabolism
- Chem4Kids: Proteins
- Chem4Kids: Enzymes
- Chem4Kids: Metabolic Cycles
- Chem4Kids: Oxygen
- Geography4Kids: Biosphere
- Geography4Kids: Food Web

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