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

Page history last edited by Nicole Lee 13 years, 7 months ago


A.  Daily Blog



      Today, September 24th, 2020, the class reviewed over multiple topics within chapter 5.  The class first discussed the leaflets (the layers) of the cell membrane phospholipid layer.  Dr. Weber explained how the extra- cellular leaflet would attach to other cells.  The class also learned that the extracellular leaflet is also an extremely important factor in recognizing other cells.  The class also learned about glycoprotein.  Glycoproteins are essentially proteins with sugars attached to it.  This step is EXTREMELY important in recognition.  Another topic the class learned about was how phospholipids were formed and how they get to the cell membrane.  The phospholipids were made in the smooth ER, where they were then transported off to the Golgi apparatus through vesicles.  From here, the vesicles take the phospholipid to the membrane of the cell, where it then uses the proccess of endocytosis to place phospholipids.  The class also discussed other topics such as domains which are proteins that fold independantly. 

     During today's class I was confused with some of the topics, one including how phospholipids are made.  However, after listening to Dr. Weber's lecture on their formation I know understand better.  However, i am still a little bit confused so I will go home and read over the notes and look up a silly youtube video to helpme understand the material!  One thing that helped me in class on the material was when Dr. Weber had the students collaboratively work on a question he presented.  Collaborative work and you tube videos always help me learn.  It would be really appreciated if we did more in class activities as a whole:).





Today, October 1, 2010, the class discussed the membrane transport in the cell.  The class learned that the membrane is selectively permeable and that its structure ensures that essential molecules must enter, that metabolic intermediates remail, and that the waste product exits.  The class also discussed how they are able to be permeable. The reason being is that their lipid tails are hydrophobic, pointing to the inside and their hydrophilic ends are facing outwards.  The class also discussed some samples that can and con not pass through the membrane easily.  One example of this is urea.  Urea is less non- polar so it is much harder for it to pass through the membrane.  However for diethyl urea, the addition of two non-polar ethyl groups makes the molecule far more hydrophobic than urea.  In reality, the rate of passive diffusion through a phospholipids bilayer of diethyl urea is about 50 times greater than urea.  Another thing the class discussed were two laws used in science many times.  One of them being that energy can never be created or destroyed; it’s just converted from one form to another. That example was the law of conservation of energy.  Another law the class discussed stated that disorder in the universe is always increasing- disorder is entropy to be exact.  What is bad in this case? Equilibrium.  Like Dr. Weber said, “a cell at equilibrium is what I like to call a dead cell”.  Molecules like moving around all of the time, they like having their personal space just like you and me, causing them to have the urge to spread out.  When these molecules want to spread out, they have potential energy.  One thing I enjoyed about class today were all of the collaborative questions Dr. Weber had us do.  I felt like they made the learning experience much better and more entertaining (no offense if that in any way offended you).  The class also discussed that the inside of the cell is basically negative and the outside of the cell has a positive charge.  Channels form an open passageway for the direct diffusion or ions or molecules across the membrane, most are gated, aquaporons.  The class also learned some information about transporters:

  • ·       Also known as carriers
  • ·       Conformational change transports solute
  • ·       Principal pathway for the uptake of organic molecules such as sugars, amino acids, and nucleotides

One thing I was actually having a little problem with in class was the whole idea of the gradient but I will look over the eBook some more and if I have any further questions I will be sure to ask Dr. Weber!  I enjoyed today’s class and I can’t wait for next week’s!


P.S. you still have to listen to the song Fergaliscious PRIOR to watching my Asian video on my chapter 4 blog.  -_-



B.  Useful Materials



All right so this first video shows the cell membrane layer and briefly describes the membrane.  This video is a bit dry but it helps an extreme amount in learning the concept and structure of the membrane.


Okay so this second video is a song that sounds kind of depressing but it helps you learn the functions of the cell through a song!


C. Article


This article is essentially an overview of how the cell goes through it's cycles.  The first part of the article reviews over how Eukaryotic cells reproduce.  This is through two main phases, interphase and mitosis.  During interphase the cell goes through the gap phase (G1), synthesis (S), and gap phase 2 (G2).  Interphase is shown by mitosis, also known as nuclear divisi0n and cytokinesis, also known as cell division.  


  • G1- The gap 1 phase 
    • During this phase the cells begins at the ccompletion of mitosis and cytokenisis and lasts until the begining of the S phase
    •  the longest of the four cell cycle phases and is quite variable in length 
    • the cell chooses to chooses either to replicate its deoxyribonucleic acid (DNA) or to exit the cell cycle and enter a quiescent state (the G0 phase)
    •  Later on in the G1 phase the cell beomescommited to replacing it's DNA
  • The S Phase
    • this stage is  Replication of the chromosomes is restricted to one specific portion of interphase
    • this typically lasts about 6 hours
    • this is the initial part of DNA synthesis
    • each chromosome replicates exactly once to form a pair of physically linked sister chromatids
    • A pair of centrioles duplicate during the S phase
  • G2 Phase
    • Follows the S phase
    • Also known asthe gap phase

The rest of the article breifly describes the parts of the M stage (the overlapping process of mitosis and cytokenisis).  Mitosis contains the five stages known as prophase, prometaphase, metaphase, anaphase, and telophase.  Each step carries out critical roles that effect the cell.




Comments (1)

Derek Weber said

at 3:24 am on Nov 23, 2010


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