October 21, 2007

The Mitochondrion Pt. 1 — Structure and Layout

Posted in Cell Biology at 3:59 am by D. Borst

So we learned in grade school that the mitochondria is the cell’s energy powerhouse. Lets expand upon that a little bit.

Mitochondria (along with chloroplasts and other plastids) are thought to have originally been independent entities. As such, they had their own DNA, the remains of which can be found in the mitochondria in our cells. It is thought that originally a mitochondria was endocytosed but never fully digested by a early pre-eucaryote. Over time, mitochondria have come to develop a symbiotic relationship with eucaryotic cells, to the point where all but a handful of the mitochondiral genome is now present in the host genome. The mitochondria in turn provides its host cell with incredibly large ammounts of ATP by processing Acetyl-CoA in the Krebs Cycle.

There are two views of the noble mitochondria, one in which it is a small, rigid little bean shaped organelle that is somewhat static in its shape and size, and the other, more recently supported view that the mitochondria is a dynamic and quickly changing organelle. Mitochondria are now thought to quickly change conformation, bind and split with other mitochondria, and in some case form one huge reticulated super entity. Two theories attempt to explain our earlier oversight:

  • One is that when isolating the parts of the cell, the contents were disrupted in order to get them out of the plasma membrane. However, this disruption also caused the mitochondrial membrane to be split in many places leading to smaller mitochondria to be characterized by explorers.
  • The other theory has to do with or techniques for looking at the cell, and how they are based upon actual or optical sectioning of the cell (i.e. physically sectioning or by using a particular focusing plane, which led to the observation of individual small mitochondria that were connected out of the section.
  • In any case, the new model suggests that mitochondria are much more fluid and less bean shaped than what you may see in your textbook, so remember that.

    Structure of Mitochondria

    The structure of the mitochondria is one of the important epigenetic features of the cell. Cells in which mitochondria or chloroplasts have been ”zapped” are not able to reconstruct the mitochondria. Rather the information to construct mitochondria seems to be contained within the structure of the mitochondria themselves. The mitochondria somehow, and Im not clear on the details, replicate themselves without being directly reliant upon cell machinery. Similarly, mitochondria are not regulated during the cell cycle, but it is just a matter of brownian motion that all cells splitting off get some mitochondria. The mitochondria then regulate their own replication (or expansion in the case of the reticulated mitochondrial super entity.

    Mitochondria have two membranes, an outer and an inner. The outer membrane has a whole bunch of porin transporter molecules that allow molecules of 5 kd or less to easily diffuse across the membrane. It, along with the inner membrane, forms a intermembrane space that is semicontinuous with the cytosol. This semi-continuity is important for the proton gradient that is generated across the inner membrane. The outer membrane of the mitochondria has proteins responsible for fatty acid elongation.

    The inner membrane is solid, and jam packed full of proteins. It is estimated that there is one protein for every 3 lipid molecules in the inner membrane. The inner membrane contains special lipid molecules termed ‘cardiolipids.’ These lipids have four fatty acid tails rather than the two that most membrand lipids have. It is continuous with itself, and forms an inner “matrix space” where the more important processes to energy production occur. This matrix space also contains the remains of the mitochondria’s own DNA, which because the mitochondria is highly conserved, has been useful for relatedness studies, i.e. mitochondrial eve. The inner membrane is also much longer than the outer membrane, making it fold back in upon itself to form long christae that protrude into the matrix space. This structure increases the surface area of the membrane, allowing a greater number of worker proteins to exist. ATP production is located on this inner membrane, so a greater surface area yields more possibilities for production. As will be discussed later, ATP production is driven by a proton gradient that is established across this membrane the electron transport process. Cardiolipids are thought to make this membrane more impermeable to protons because of their four tails.

    So to remember:

  • Mitochondria may have originally been free organisms that have been engulfed by proto-eucaryotes.
  • Mitochondra form dynamic entities within animal cells, quickly combining with other mitochondria to form large and irregular reticulated organelles.
  • Cells cannot make mitochondria de novo, they must inherit them from their progenitors and allow them to reproduce.
  • Mitochondria have two membranes, an outer membrane that has many porin channels within it, and a inner membrane that has special cardiolipids that make it a good barrier to protons.
  • The inner membrane of the mitochondria is the site of much of the cells ATP production.
  • That is all for this segment. The information for this post came from two sources–either Alberts’ Molecular Biology of the Cell, or the October 17 Cell Biology lecture by Dr. Todd Rosentiel at PSU.

    Powered by ScribeFire.



    1. J.P.Nema said,

      Kindly specify F0-F1 particle on inner membrane Cristae.

    2. khan said,

      very very good

    3. khan said,

      give the detail about mitochondrial membrane

    4. khalid said,

      what is the role of golgi apparatus in mitochondria

    5. khan said,

      what is the composition of F1 particals

    6. sammy said,


    7. magalin said,

      i think you gave alot of info. or just the right amount that i needed to complete my work.

    8. raman said,

      thank you

    9. Ben said,

      Very useful for a cell part project im working on.

    10. Oppy said,

      Thank you, you had more in-depth analysis than my AP Bio book :)



    12. Kavitha said,

      Thank u…it really helped me to prepare for my seminar the topic – “mt DNA”

    13. joseph said,

      not enough info on d cell death part but thanks any way

    14. nidhi said,

      the info was quiet helpful for my 3d bio project

    15. ravi kota said,


    16. nice! i’m gonna make my own blog

    17. Bob said,

      Lol. That was cool. Science is cool.

      • me said,

        bob, i totally agree. this is too awesome for words to describe. dude who made this, i salute you ;)

    18. Pie said,

      Ooh, thanks for posting this! Now I can confuse my classmates tomorrow!

    19. abby and licete said,

      thanx for the info science nerds hahaha

    20. bob the builder said,

      i am going to go build a mitochondria structure jk

    21. Napel said,

      its really good and help full

    22. me said,

      am i the only one who gets really turned on by this website? i thought not. ;p

    23. adnan said,


    24. M.J.Halpern said,


      I have the pleasure to announce my web site

      Cell Physiopathology
      Tissues Physiopathology
      Skin Physiopatology
      Bone Physiopathology
      Joints Physiopathology

      Lipids and atherosclerosis
      Wine and health

      Muscle physiopathology

      If you want to be informed about the publication data of the next items, please send me a mail
      If you have priority for some of the items, please let me know

      Sincerelly yours
      Prof. M.J.Halpern

    25. jasarat said,


    26. yogeshwar said,

      it very useful structure

    27. 3142612 said,

      3142612 beers on the wall.

    28. Wonderful blog! I found it while surfing around on Yahoo News. Do you have any tips on how to get listed in Yahoo News? I’ve been trying for a while but I never seem to get there! Many thanks

    29. I like this web site because so much useful stuff on here : D.

    30. life.|Good journey and experience!|Great journey and experience!|Very good journey and experience!|Wonderful journey and experience!|good information you

    31. Heya! I just wanted to ask if you ever have any problems with hackers? My last blog (wordpress) was hacked and I ended up losing many months of hard work due to no data backup. Do you have any solutions to protect against hackers?

    32. Roacheroche said,

      The following time I learn a weblog, I hope that it doesnt disappoint me as much as this one. I imply, I know it was my option to learn, but I really thought youd have something attention-grabbing to say. All I hear is a bunch of whining about one thing that you could possibly fix in the event you werent too busy in search of attention.

    33. Cody Petsch said,

      That is so accurate! I really don’t understand very much with regards to conditioning nevertheless this particular article actually is awesome. Thanks!

    34. This page appears to be get an excellent ammount of visitors. How can you advertise it? It provides a pleasant individual twist on issues. I assume having one thing authentic or substantial to talk about is the most important factor.

    35. Yelena Argyle 22 Jun 11 at 3 51 pm

    36. lulu233 said,

      An impressive share, I just given this onto a colleague who was doing a small analysis on this. And he actually bought me breakfast because I discovered it for him.. smile. So let me reword that: Thnx for the treat! However yeah Thnkx for spending the time to discuss this, I truly feel strongly about it and love reading extra on this topic. If potential, as you turn into experience, would you thoughts updating your weblog with more particulars? Its extremely helpful for me. Massive thumb up for this weblog post!

      • yomama said,

        this is bs i dont know why you like it asshole

    37. Kieth Izaguine said,

      I am glad to be one of the visitors on this outstanding site (:, thankyou for posting .

    Leave a Reply

    Fill in your details below or click an icon to log in:

    WordPress.com Logo

    You are commenting using your WordPress.com account. Log Out /  Change )

    Google+ photo

    You are commenting using your Google+ account. Log Out /  Change )

    Twitter picture

    You are commenting using your Twitter account. Log Out /  Change )

    Facebook photo

    You are commenting using your Facebook account. Log Out /  Change )


    Connecting to %s

    %d bloggers like this: