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Chapter 4 Blog: General Features of Cells (Pankhuri)

Page history last edited by Pankhuri Garg 13 years ago


A.  Daily Blog


9/22/2010 (submitted 9/23/2010)


Today's lecture started without the text poll. Wonder where that is. We talked about the similarities and the differences between the types of cells, Prokaryotic cells and Eukaryotic cells. Prokaryotic cells are mainly bacteria and archaea. Eukaryotic cells are what plants, animals, and humans are composed of. Eukaryots are plasma membrane enclosed and DNA is located in an enclosed nucleus. These cells exhibit compartmentalization, which means everything is separated by membranes into organelles. Example of different organelles are mitochondria, ribosomes, lysosomes, peroxisomes, rough/smooth endoplasmic reticulum, and golgi apparatus. . From what I understand, Prokaryotic cells on the other hand a essentially a "one large organelle". The DNA is located in a central nucleoid region. There are free floating ribosomes in the cytoplasm. Both contain a plasma membrane, ribosomes (protein making units), cytoplasm, and DNA. Also, plant cells, a variety of Eukaryotic cells, also contain a herd cell wall like the prokaryotics cells. Eukaryotic cells are much larger in size. This whole part was a review though considering we have been learning the same information since 9th grade, but it was a great memory refresher because i know i probably forgot some things mentioned. We then talked about proteins and protein trafficking. I am confused about protein trafficking, but I'm going to attempt to explain it. Prior to the last couple of lectures, I thought the only way protein can be made, was then mRNA came into the cytoplasm and then was synthesized, and from there it did what it had to. Well that is true, but thats only one type called post-translational out of the three. And in that, after the protein is synthesized, a section of the amino acid chain contain the signals for where it has to go. The other is y-cytosol. This is pretty much the same as post-transitional, except the synthesized protein just stays in the cytosol, I'm guessing for emergency purposes (Dr. Weber, please correct if I'm wrong). The last type is cotranslational. The protein is made in the cytoplasm, then sent to the rough endoplasmic reticulum to be synthesized, and then to the golgi apparatus for further specialization, and then finally sent out.  So overall, it was confusing but "knowledge giving" lecture. 


9/24/2010 (submitted 9/24/2010)


Dr. Weber told us that he ordered 28 4G iPod Touches for us, for better learning opportunities. Sadly, administration won't let us keep them. Something new and exciting! We talking in detail about protein trafficking. And focused mainly on cotranslational modification of proteins, which was great because that is the one I was most confused about. There are two types of proteins synthesized by cotranslational, membrane and secretory. The RNA is replicated from the DNA, from which mRNA is replicated. mRNA leaves the nucleus and comes into the cytoplasm. In the cytoplasm, free floating ribosomes assemble to start synthesizing the mRNA to form a amino acid sequence. The amino acid sequence begins with a 20 amino acids (mostly hydrophobic) , known as the ER signaling sequence, which signals the protein to be synthesized into the ER. Signal Recognition Particle (SRP) binds to this specific sequence, and carries the entire arrangement of ribosomes, tRNA, mRNA, etc. to the Rough ER. Once there, protein synthesis starts, while the new protein chain is being fed into the ER lumen. Dr. Weber then asked us what would happen if the first 40 amino sequences were lost. We figured that the protein would not go where to go since the ER signaling sequence is within the first 40 amino acids. The protein would eventually disintegrate. This condition is called Cystic Fibrosis. Another new random thing I learned was about Diabetes. The proteins for diabetes are secretory proteins made by, obviously, cotranslational modification. Diabetes Type I is possibly caused because, like cystic fibrosis, the proteins for normal blood sugar don't have signals for a complete synthesis and the protein disintegrates. Diabetes Type II is caused when proteins are being produced, but as a much slower rate. Also, Type II can become Type I, but the reverse cannot happen. 


B.  Useful Materials


1. Eukaryote and Prokaryote Cells - This is game about the two types of cells. Almost designed like "who want's to be a millionaire?", the more answers you answer you answers correctly the more money you "earn". Great to revise the differences and the similarities between the two cell types. It also asks questions about the composition of specific things from each cell. I reached $4,000 =D


2. A Systematic Approach to Protein Glycosylation Analysis: A Path Through the Maze - This PubMed article talks about a important aspect of post-translational modification. Protein Glycosylation alleviates the functional diversity of a newly synthesized proteins and alters the biological activity. These functions include molecular trafficking, self-recognition, and clearance. Studying the basis of these functions is a tough task because glyco-proteins are themselves made through very complex steps and are diverse. 


3. Protein Trafficking (Embedding Disabled, Sorry) - This video is a virtual animation of protein trafficking. It explains what happens to proteins after they are formed and how they are modified and packaged. 




Comments (1)

Derek Weber said

at 3:02 am on Nov 23, 2010

Great job.

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