Mitochondria (singular, mitochondrion) are primarily concerned with the chemical processes by which energy in the form of adenosine triphosphate (ATP) molecules is made available to cells (Chapter 4). Most of the ATP used by cells is formed in the mitochondria by a process that consumes oxygen and produces carbon dioxide.

Mitochondria are spherical or elongated, rodlike structures surrounded by an inner and an outer membrane (Figure 3-14). The outer membrane is smooth, whereas the inner membrane is folded into sheets or tubules known as cristae, which extend into the inner mitochondrial compartment, the matrix. Mitochondria are found throughout the cytoplasm. Large numbers of them, as many as 1000, are present in cells that utilize large amounts of energy, whereas less active cells contain fewer.

Vander et al.: Human Physiology: The Mechanism of Body Function, Eighth Edition

I. Basic Cell Functions

3. Cell Structure

© The McGraw-Hill Companies, 2001

Cell Structure CHAPTER THREE

Cell Structure CHAPTER THREE

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Mitochondrial Function

■ lumen of granular endoplasmic reticulum

■ lumen of granular endoplasmic reticulum




Inner membrane

Inner membrane

Outer membrane


Structure: Rod- or oval-shaped body surrounded by two membranes. Inner membrane folds into matrix of the mitochondrion, forming cristae.

Function: Major site of ATP production, O2 utilization, and CO2 formation. Contains enzymes of Krebs cycle and oxidative phosphorylation.


Mitochondrion. %

Electron micrograph courtesy of

Mitochondria have small amounts of DNA that contain the genes for the synthesis of some of the mitochondrial proteins. Evidence suggests that cells gained mitochondria millions of years ago when a bacteria-like organism was engulfed by another cell and, rather than being destroyed, its metabolic functions became integrated with those of the host cell.

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Essentials of Human Physiology

Essentials of Human Physiology

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  • Monika
    What is the function of the inner membrane folds of the mitochondria?
    8 years ago
    What is the statate of function of the mitochondria?
    8 years ago

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