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Chapter 5 Blog:  Membrane Structure, Synthesis, and Transport (John T)

Page history last edited by John Tamanas 13 years, 7 months ago

In the first section of this page, you will write a daily summary of that day's class.  For example in  your chapter 2 blog, your first entry should be titled 9/3/10.  You should then write a one or two paragraph summary of that day's lecture, outlining the major points.  In the second section, you are required to add two items (link to a website, video, animation, student-created slide show, student-created PowerPoint presentation) and one journal article pertaining to a topic in this chapter.  A one-paragraph summary must accompany each item describing the main idea and how it applies to the lecture topic.  Please see the PBWorks help guide for assistance embedding video and other items directly in the page.  I will also produce a how-to video on using tables to wrap text around items and other useful tips.  Please see the syllabus for organization and grading details.


A.  Daily Blog


9/29/2010: Captain's Log. Bio-lecture day 8. The polleverywhere.com text-in-your-answer polls seem to be malfunctioning once again. This time, however, the cause seems to be the lack of saving by General Doctor Weber. After a very brief period of despair from the General and the class, we went on to discuss one of the main parts of a cell, the plasma membrane. Plasma membranes are made up of a phospholipid bilayer. These two layers help keep the inside, inside, and the outside, outside. The plasma membrane is constantly building up and breaking down. It builds up as phospholipids from the smooth ER are transported to the Golgi and then combine to the plasma membrane via exocytosis. The plasma membrane breaks down via endocytosis. 

     We also learned about transmembrane proteins. These proteins fall under the category of co-translational proteins. When the ribosome is making these proteins in the rough ER, however, they stay in the plasma membrane instead of being released into the lumen of the rough ER. When it is being translated the N-terminus is in the lumen.  Then when the phospholipid bilayer that it was translated on attaches to the plasma membrane, the N-terminus is facing the extracellular matrix and the C-terminus is facing the cytosol. Captain out.


10/1/2010: Captain's Log. Bio-lecture day 9. Today's discussion was about protein transport across the plasma membrane. The first thing we covered were the first two laws of thermodynamics: Energy can never be destroyed or created and entropy in the universe is always increasing. Using these laws we can assume that equilibrium is the most disorderly and that concentration gradients are very unstable due to their high potential energy. Cells allow diffusion to occur passively with passive transport. They use  channel proteins (proteins that are pretty much tunnels/openings. They are not very selective) to do this. Since concentration gradients diffuse automatically cells must take this into account so they don't die. Cells use facilitated diffusion with carrier proteins (These are selective proteins that act like gates. They are only open on one side at a time, and only allow certain particles in and out of the cell) to diffuse larger molecules and charged ions across the plasma membrane. Carrier proteins can also act in active transport. Active transport creates concentration gradients. Active transport's energy is derived from ATP. Lastly, we went over the three different kinds of proteins: Uniporter (one ion/molecule), symporter (2+ ions/molecules in opposite directions), and antiporter (2+ ions/molecules transported in different directions). Captain out.


10/6/2010: Captain's Log. Bio-Lecture day 10. The lecture class today was mostly a review. We did, however, discuss the experiment done to discover aquaporins. Captain Commander General Dr. Weber, being the sneaky man he is, found a way to connect this with the review as well. Basically, the experiment consisted of putting CHIP28 (the protein they were testing) into a frog oocyte and seeing the rate of water diffusing through the membrane. The CHIP28 oocyte's rate of water diffusion was so much greater than the control's that the cell lysed (Or asploded as I like to call it). Captain out.


B.  Useful Materials


Submitted 10/3/2010:

This video describes the different ways particles traverse the plasma membrane. More specifically, it talks about passive diffusion, facilitated diffusion, primary active transport, and secondary active transport. It even talks about the sodium-potassium pump!



Submitted 10/3/2010:





PURPOSE OF REVIEW: Hypomagnesaemia has recently been recognized as a rare, but severe, complication of proton pump inhibitor (PPI) use. We reviewed all the cases published to date in peer-reviewed journals to summarize what is known of the epidemiology, risk factors, cause and treatment.

RECENT FINDINGS: Hypomagnesaemia has been described with all substituted pyridylmethylsulphonyl benzimidazadole derivatives and is a class effect, recurring with substitution of one PPI for another. A long duration of use and high rates of adherence are probably risk factors, but the prevalence is unknown. The diagnosis is often missed, despite the severe symptomatology. Renal magnesium handling is normal, so implicating impairment of net intestinal absorption as the proximate cause. It is not known whether this is the consequence of defective absorption of magnesium through the active or passive transport processes, or increased losses.

SUMMARY: PPI-associated hypomagnesaemia is a rare, but potentially life-threatening, side-effect that has emerged only in the era of mass use of these agents. The cause of hypomagnesaemia remains poorly understood, but it responds rapidly to withdrawal of the PPI."



This article talks about the condition hypomagnesaemia and how it relates to the proton pump in cells. In lecture we learned how cells use the proton pump in order to create an electrochemical gradient. With this gradient, the cell brings in other nutrients. Hypomagnesaemia results from a complication in the proton pump inhibitor.


Submitted 10/3/2010:

This video is what the kids today would call "loltastic". This video somewhat shows how facilitated diffusion "through the eyes of two sugars" It shows that sugars can't cross over plasma membranes and only certain carrier proteins allow them to enter. 


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