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.
Use the study guide below to navigate through this unit. The links lead to answers to the questions, in case you can't remember. If you can answer these questions, you will do well on the exam.
Read pp 387-402 in Cooper
Use the excellent diagrams to
show how the different mitochondrial systems are interrelated and also how
proteins enter mitochondria. Study
the section on mitochondrial diseases and understand how they are
inherited. Finally, correlate
your learning from pp 398-402 with the biochemical lectures during the
previous week to fully understand the chemiosmotic theory.
Objectives of the unit on mitochondria.
- Describe the basic substructure of mitochondria. Be able to correlate a change in structure with a change in function.
- Locate each of the major sets of enzymes/functional groups: Kreb’s Cycle, Electron transport chain, ATP synthetase, hydrogen pumps and describe their significance.
- Be able to specify exactly where and on what structures ATP is synthesized.
- Define the Chemiosmotic theory.
- Explain the significance of an abnormal increase in number of mitochondria and/or cristae in cells that have defective mitochondrial proteins.
- Describe how mitochondria replicate.
- Define the function of mitochondrial DNA, RNA, ribosomes. Categorize the proteins produced.
- Distinguish mitochondrial inheritance from Mendelian inheritance.
- Describe general functions for TOM and TIM proteins in mitochondria.
- List the major steps involved in protein entry into mitochondria (preparation, binding, guiding, entry, final steps in matrix).
- Describe how products of mitochondria may leave for the cytoplasm.
- Describe how the electron transport chain facilitates the following:
- Define the steps used by the cell to destroy old mitochondria
- Describe how mitochondria are involved in steroid hormone production.
- How are mitochondria involved in apoptosis?
Competencies
Given
the origin of a specific mitochondrial protein, be able to trace its route
into mitochondria and be able to predict the general outcome of a genetic
defect in the protein.
Describe
multiple examples where mitochondria functions are integrated and thus
facilitate one another.
Be
able to explain mitochondrial heredity to a patient and, if there is a
defect, why there is variability in severity of the disease in a given
family.
Test yourself!! How much do you already know about mitochondria?
 | How are mitochondria organized to be powerhouses? Where are each of the major systems? |
| Mitochondrial Geography: Trace the structural pathway 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 mitochondria exchange ATP and ADP? |
| How are mitochondria involved in steroid hormone production? |
Sample questions:
1) Your patient has a genetic defect in a mitochondrial Kreb’s cycle protein encoded by nuclear DNA. The defect is not in or near the signaling sequence, however it prevents the protein from being folded into its proper 3-dimensional structure. At what point in its route to its destination will the defect be a problem:
|
a. Chaperone interaction in the outer membrane |
|
b. Chaperone interaction in the matrix |
|
c. Binding to TOM proteins |
|
d. Transport through the General Import pore |
|
e. Binding to TIM proteins |
Answer: B
2) The hydrogen pumps on the electron transport chain directly or indirectly facilitate the following:
|
a. Chaperone binding to proteins in the cytoplasm |
|
b. Transport through the general import pore |
|
c. ADP/ATP Exchange |
|
d. Production of ATP |
|
e. All of the above |
Answer: E
Last updated:
08/27/03
visitors since 8/09/01
URL:
http://www.cytochemistry.net/cell-biology/mitochondria_Intro.htm
childsgwenv@uams.edu
text © copyright 1996 Gwen V. Childs, Ph.D.