Mitochondria

Bobbie Teng

mitochondrion.jpg



~Membrane enclosed organelle found in most eukaryotic cells.
~ major function: supply of adenosine triphosphate
~ other functions: signaling, cellular differenation, cell death, as well as the control of the cell cycle and cell growth.

Outer Membrane
~ porins
~ larger proteins can cross with "permission"
~ Disruption of the outer membrane leads to cell death
~ Enzymes involved with other activities.

Intermembrane Space
~ concentrations of small ions is the same as the cytoplasm
~ concentration of proteins is different than the cytoplasm

Inner Membrane

~ forms internal compartments (cristae) that maximize space for proteins to function properly and efficiently
~ contains ATP synthase
~ contains specific transport proteins that regulate metabolite passage into and out of the matrix
~ contains electron transport chain and transport proteins for phosphorylation
~ impermeable

Cristae
~ studded with proteins
~ maximizes surface area for chemical reactions to occur


Mitochondrial_Electron_Transport_chain.jpg


Matrix
~ contains soluable enzymes that catalyze small organic molecules and fatty acids
~ citric acid cycle
~ contains the mitochondria's DNA and ribosomes
~ site for oxidation of organic molecules

Dr. Lynn Margulis of the University of Massachusettes proposed an exracellular origin of the mitochondria.



Bibliography

"Crista." Wikipedia. 15 Oct. 2008. 25 Oct. 2008 <http://en.wikipedia.org/wiki/Crista>.

"Evolutionary Origin of Mitochondria." Experimental Biosciences. Ed. David R Caprette. 26 May 2005. Rice U. 25 Oct. 2008
<http://www.ruf.rice.edu/~bioslabs/studies/mitochondria/mitorigin.html>.

"Inner Membrane." Wikipedia. 15 Oct. 2008. 25 Oct. 2008 <http://en.wikipedia.org/wiki/Inner_membrane>.

"Matrix (biology)." Wikipedia. 15 Oct. 2008. 25 Oct. 2008 <http://en.wikipedia.org/wiki/Matrix_(biology)>.

"Mitochondrion." Wikipedia. 15 Oct. 2008. 25 Oct. 2008 <http://en.wikipedia.org/wiki/Mitochondrion>.

"Outer membrane." Membrane." Wikipedia. 15 Oct. 2008. 25 Oct. 2008 <http://en.wikipedia.org/wiki/Outer_membrane>.


Mitochondria Structure and Function

By: Ashley Espy



mitoch.gif


  • Mitochondria is a membrane-enclosed organelle found in most eukaryotic cells
  • It generates most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. The ATP is produced in the mitochondria using energy stored in food.
  • Mitochondria are involved in a range of other processes, such as signaling, cellular differentiation, cell death, as well as the control of the cell cycle and cell growth
  • A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins
  • Mitochondria contain an outer mitochondrial membrane, the intermembrane space (the space between the outer and inner membranes), the inner mitochondrial membrane, the cristae space (formed by infoldings of the inner membrane), and the matrix (space within the inner membrane).

Outer Membrane


  • It contains large numbers of integral proteins called porins. These porins form channels that allow molecules 5000 Daltons or less in molecular weight to freely diffuse from one side of the membrane to the other.
  • Disruption of the outer membrane permits proteins in the intermembrane space to leak into the cytosol, leading to certain cell death.

Inner membrane


  • The inner mitochondrial membrane contains proteins with four types of functions.
  1. Those that perform the redox reactions of oxidative phosphorylation
  2. ATP synthase, which generates ATP in the matrix
  3. Specific transport proteins that regulate metabolite passage into and out of the matrix
  4. Protein import machinery
  • The inner membrane does not contain porins and is highly impermeable to all molecules.

Cristae

  • The inner mitochondrial membrane is compartmentalized into numerous cristae, which expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP.
  • They are studded with proteins, including ATP synthase and a variety of cytochromes.

Matrix



  • The matrix is the space enclosed by the inner membrane. It contains about 2/3 of the total protein in a mitochondrion.
  • The matrix is important in the production of ATP with the aid of the ATP synthase contained in the inner membrane.
  • The matrix contains a highly-concentrated mixture of hundreds of enzymes, special mitochondrial ribosomes, tRNA, and several copies of the mitochondrial DNA genome.
  • Of the enzymes, the major functions include oxidation of pyruvate and fatty acids, and the citric acid cycle.


protein.gif

Protein Unfolded by Mitochondria


The mitochondrial protein import machinery. Shown is the import pathway of a matrix protein. The preprotein is synthesized in the cytosol with an N-terminal positively charged presequence. Cytosolic chaperones can bind to the preprotein. The translocase of the outer mitochondrial membrane (TOM) contains receptors that recognize the presequence and a general import pore (GIP) that mediates translocation across the outer membrane (OM). The translocase of the inner membrane (TIM) includes an import channel formed by Tim23 and Tim17 and the peripheral subunit Tim44. The membrane potential
Delta
Delta
psi
psi
across the inner membrane (IM) drives translocation of the presequence. Matrix Hsp70 (mtHsp70) binds the preprotein in transit and, together with Tim44 and the co-chaperone Mge1, forms an ATP-dependent import motor. The presequence is cleaved off by the mitochondrial processing peptidase (MPP). IMS, intermembrane space.


Mitochondrial DNA


  • Mitochondria have a small amount of their own DNA.
  • Mitochondrial DNA contains 37 genes, all of which are essential for normal mitochondrial function. Thirteen of these genes provide instructions for making enzymes involved in oxidative phosphorylation.
  • The remaining genes provide instructions for making molecules called transfer RNAs (tRNAs) and ribosomal RNAs (rRNAs), which are chemical cousins of DNA.

Diseases


  • Mitochondria have been implicated in a variety of human diseases, including mental disorders, aging, diabetes, atherosclerosis, heart failure, myocardial infarction, stroke and other ischemic-reperfusion injuries, neurodegenerative diseases including Alzhiemer’s and Parkinson’s diseases, cancer, HIV, sepsis and trauma with multiorgan dysfunction or failure.

mitochondrial-disease.gif


Research on Mitochondria


  • The Mitochondrial Research & Innovation Group at the University of Rochester Medical Center are conducting research on Mitochondria and human diseases. The vision of the MRIG is to become the leader in research on the role of mitochondrial dysfunction in human disease. They want to merge the sciences of chemistry and biology with clinical medicine in developing safe and effective mitochondrial-targeted therapeutic agents that reduce or prevent oxidative damage and enhance the efficiency of mitochondrial energy production. Experienced pharmaceutical-industry-derived consultation on drug development from the MRIG as well. Shey-Shing Sheu is the scientific coordinator of MRIG and specifically works on Calcium signaling in normal and diseased hearts and neurons.


Bibliography


"Mitochondrion ." Wikipedia . 14 Oct. 2008. 21 Oct. 2008 <http://en.wikipedia.org/wiki/Mitochondrion>.
"Introduction to MRIG." Mitochondrial Research and Innovation Group. University of Rochester Medical Center . 14 Oct. 2008. 21 Oct. 2008 <http://www.urmc.rochester.edu/mrig>.
"Mitochondrial DNA." Genetics Home Reference . 20 Oct 2008. U.S National Library of Medicine . 15 Oct. 2008. 21 Oct. 2008 <http://ghr.nlm.nih.gov/chromosome=MT>.
Spurger, Linda . "Mitochondria: Architecture Dictates Function." University of Texas Medical Branch: Cell Biology . UTMB. 15 Oct. 2008. 21 Oct. 2008 <http://cellbio.utmb.edu/cellbio/mitoch1.htm>.