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Chapter 4 Blog: General Features of Cells (Siddarth)

Page history last edited by Siddarth Santhebennur 13 years, 8 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

September 22, 2010: To start off class we discussed about the different kinds of cells. I remember going over information on the cell in our Biology Class (9th grade) as well as in Anatomy and Physiology(Last year). We stared to talk about the different cells that we find which are Eukaryotes and Prokaryotes. The main differences between Eukaryotes and Prokaryotes are: Eukaryotes have a nucleus whereas Prokayotes don't, Eukaryotes have membrane-bound organelles and Prokaryotes don't have membrane-bound organelles (however they do have a few organelles). We then discussed the common things that are found in all cells which are: DNA, ribosomes, and Plasma Membranes. Even though all cells within an organism have the same DNA, their functions can be different. Why do cells with the SAME DNA have DIFFERENT functions? That can be explained in two words: Gene Expression. The function of the cell is dependent on how the genes in the cell are expressed. For example, a muscle and nerve cell both have the same DNA, however they have two completely different functions. This is because the proteins being created are used for different purposes. As stated in a previous lecture "Proteins help determine the function of the cell". We then moved on to the Endomembrane system which is basically a system that keeps everything out in the cytoplasm. When I say everything, I am referring to the products made in this system. In this case it is proteins. We got to see the movement of proteins from when they were created to when they left to their destination.

     Dr. Weber showed us an experiment (which was in the reading as well) of how scientists were able to track the proteins being concentrated in the Rough ER and then transferred to the Golgi Apparatus where it was modified. Finally after being modified, the proteins leave the cell through exocytosis ( bulk transport by the usage of vesicles). The experiment done was very interesting because it showed the factual information that we have been reading in our books being played in real life. Some people just like to read facts and information and accept it as a fact. Personally, I find it easier when I see the facts in real life. To put in simple words: the video was AMAZING! Towards the end of class we discussed about the "Fate of proteins" and where they may end up. I am sure we will pick up that topic on Friday!


September 24, 2010: Today in class, we picked up the discussion of the "Fate of Proteins". I learned that proteins go through 1 of 3 methods to reach their destination. One of the destinations that proteins could end up in is the cytoplasm. Usually this is just carried out by a free ribosome. Once translation has has occurred, the proteins basically lie in the cytoplasm and can be used for various purposes. Another place where proteins could end up is in the Rough ER. This is also known as Co-Translation. So basically, when the ribosomes carry out translation the amino acids start to come out the other end. Within the first 20-40 amino acids, an "ER Signal Sequence" is formed due to the coding of the mRNA. The ER Signal Sequence is what allows the protein structure to end up in the ER. Along with the Signal Sequence, SRP (Signal Recognition Particle) is needed to act as a transporter and bring the protein to the ER. Without the Signal Sequence, the proteins would not be able to be transported to the ER. In class, we discussed what would happen if a channel protein was needed for Cl- but the first 40 amino acids were not created during translation. This made us think back to what we had discussed during the process of Co-Translation. We concluded that the ER Signal Sequence would have not been there to let the SRP know when to pick the protein up. We also discussed the fate of the proteins after they got sent to the Rough ER. We watched an animation of how the proteins are moved from the ER to the Golgi Apparatus. It talked about how the proteins got modified in the golgi and where then transported outside of the cell via secretory vesicles. 

     The last place where proteins can end up is in semi-autonomous organelles. This is known as Post-Translation. Examples of these would be the mitochondria, chloroplast and even the nucleus. The method of transportation for these proteins is very similar to the method in Co-Translation. Instead of an SRP brining the proteins to the organelles, there are transport proteins that carry the newly-formed proteins to the organelle AND help fold it into its final structure. This way, the protein is ready to be used within the organelle it is transported to. Towards the end of class, we had a text poll that was related to the membrane of cells (specifically the plasma membrane). The question was related to the cholesterol and the fatty acid chains within the phospholipid bilayer. To tell you the truth, I still did not understand why the fatty acids would get shorter in order for the membrane to become more organized. That is something I am going to have to look into! Ever wonder if we did not have proteins in our lives? Actually, I think I already know the answer to that question. We probably would not be here. Scary right?


B.  Useful Materials

Useful Video  Description 
Protein Trafficking  http://www.youtube.com/watch?v=rvfvRgk0MfA  This is a video that basically explains how the proteins that got through Co-Translation get modified in the Golgi Apparatus. It gives a very good understanding of how the proteins are passed from the Rough ER to the Golgi and then transported out of the cell. By the way, I apologize for not embedding the video. Whenever I tried to insert the URL, it was giving me some problems. 



Useful Article    Description

HAX1 deficiency: Impact on lymphopoiesis and B-cell development.




This is a very interesting article that I found on PubMed that was very similar to the question about the loss of a Cl- channel. It discuses the loss of a protein called HAX1. Scientists did a test where they created a "deficient" version of this protein that did not contain all the amino acids required to function properly. The result of this test was the a premature death at the age of 12. This is an example of what happens to an incomplete protein in the body. I'll let you read more about it because the results of this test are pretty interesting. It was the last thing that I expected to happen. 





Useful Video    Description
From RNA to Protein Synthesis    The reason I put up this video was because I did not completely understand the process of how the proteins are made by RNA. We have discussed this in previous years, but I was a bit hazy on this subject. So I decided to watch a video about. This video shows 3-D structures in action and breaks the material down and helped me out a lot. Maybe it might someone else! 



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