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

Page history last edited by Philip Wang 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



Today we learned about membrane structure, synthesis, and transport. There are two layers to a membrane structure: the extracellular leaflet, which is the top layer of a phospholipid and the cytosolic leaflet, which is the side facing the cytoskeleton. Glycoproteins, which are proteins with sugar on it, are important in recognition. Phospholipids are synthesized in the smooth ER and they start out as hydrophobic free fatty acids. Vesicles leave the ER carrying membrane cells to the Golgi's cis face. Exocytosis builds membranes and endocytosis breaks down membranes. Transmembrane proteins allow things in and out of the cell. 25% of all genes encodemembrane proteins and any error in membrane transport causes disease.




Today, we continued to learn about membrane structure, synthesis, and transport. Hydrophobicity is a major factor when considering moving molecules. Carbohydrates have a bunch of hydroxyl groups. The first law of thermodynamics is the conservation of energy: energy cannot be created or destroyed, just converted from one form to another. The second law of thermodynamics is that disorder in the universe is always increasing. Molecules naturally try to spread out and stay away from equilibrium, which is the highest state of disorder. Concentration gradients are very unstable because they have a positive charge on the outside and a negative charge on the inside. Facilitated diffusion is when channel proteins open on both sides when activated to bring things into the cell. It is nonspecific. Carrier proteins are naturally opened on one end. They have a hydrophilic pocket and are flexible. They can be used for active transport also. Uniporters allow a single molecule or ion to go in one direction. Symporters/costransporters allow two or more in the same direction. Antiporters allow two or more molecules to be transported in opposite directions.  

B.  Useful Materials

This is a video that talks about passive transport. Membranes are selectively permeable, allowing some particles to passively diffuse into the cell. Passive transport does not require energy because the particles are small enough to slip through the pores on the membrane.


This is a video that talks about active transport. When larger substances need to enter or exit a cell, active transport is used. Active transport requires energy to activate a transport protein. The protein binds with the substance, then changes its shape to release the substance into the cell.



This is an article that talks about the permeability of cell membranes. They used a model to perform simulations of restricted diffusion. When they got their results, they found that they overestimated the exchange time of diffusion. This led them to believe that we underestimate the value of cell membrane permeability.




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