Mitochondria are the cells' power sources. They are distinct organelles with two membranes. Usually they are rod-shaped, however they can be round. The outer membrane limits the organelle. The inner membrane is thrown into folds or shelves that project inward. These are called "cristae mitochondriales". This electron micrograph taken from Fawcett, A Textbook of Histology, Chapman and Hall, 12th edition, 1994, shows the organization of the two membranes.

For the discussion session, read the following pages in your text: pp 653-676 and 569-672. Alberts et al, Molecular Biology of the Cell, Garland Publishing, Third Edition, 1994

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Test yourself!! How much do you already know about mitochondria?

Describe the basic substructure of mitochondria.
How are mitochondria organized to be powerhouses? Where are each of the major enzyme groups?
Trace the steps leading from the products of glycolysis to the Kreb's cycle and the electron transport chain. What are the final products? Where does each event occur in the mitochondrion?
What is the significance of an increase in the number of cristae in a mitochondrion?
What is the structure and function of the inner membrane and elementary particles?
How do mitochondria replicate?
Are mitochondria completely dependent on nuclear DNA and ribosomes?
What happens to old, worn-out mitochondria?
If the inner membrane is so impermeable, how do proteins enter?
How do import signals work?
What happens if an import protein is defective?