Cellular Membranes and Transport
Cellular Membranes and Transport ZO331
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This 4 page Class Notes was uploaded by Cody Brazel on Monday September 7, 2015. The Class Notes belongs to ZO331 at Southeast Missouri State University taught by Dr. siegel in Spring 2015. Since its upload, it has received 39 views. For similar materials see animal physiology in Biology at Southeast Missouri State University.
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Date Created: 09/07/15
Second Week of Notes for Animal Physiology831 to 96 2015 During the class lecture Dr Seigel reviewed the outer and inner workings of the cellular membrane along with types of transport associated with said membranes Properties and Accessories of the Cell Membrane The cellular membrane is composed of a bi layer of phosphoryl lipids hence the age old term quotphospholipid bilayer Each individual phospholipid is composed of a chain of hydrophobic fatty acids and a hydrophilic phosphate group located at the head Via hydrophobic interactions the fatty acids are kept together and ensures the integrity of the cell membrane In addition molecules such as cholesterol are present in the chains of fatty acids that confer a stronger attachment between the fatty acids When you see a quotkinkquot in one of the fatty acid chains there is a double bond located in the general area of that the molecule Double confer a type of rigidity to the membrane and promote further integrity When looking at a model of the membrane one can see two different types of globular masses upon and within the cellular membrane These masses are proteins and they are labeled according to their relative arrangement to the cellular membrane Proteins that are located directly in the membrane are called integral proteins and are useful in facilitating transport and creating channels Proteins that are located on the protein but not fully implanted into the bilayer are called peripheral proteins Peripheral proteins are useful for information gathering and communications between cells The half of the bilayer that is contact with the extracellular matrix is called the outer leaflet and the inner leaflet is in contact with the cytoplasm of the cell In each case proteins of the cell are responsible for 4 different processes in the cell 1 Transport channels carriers symports 2 Receptors 3 Enzymes 4 Structural support Types of Transport There are two types of transport associated with cellular membranes Passive and active Transport 0 Passive Transport Utilizes the natural tendency for molecules to go down their concentration gradient This process end goal is to reach equilibrium between the extracellular matrix and the cell itself Since the process does not go against the concentration gradient of the molecules no energy is required Passive transport comes in two types Basic and Facilitated 0 Basic Transport Membrane permeable molecules like gases nonpolar molecules and small polar molecules H20 are allowed to diffuse through the membrane without the need of facilitations via proteins 0 Facilitated Diffusion Membrane impermeable molecules such as ions and large polar molecules also diffuse down their concentration gradient but need proteins to facilitate the diffusion o The permeability of membranes depends on temperature concentration gradient and surface area and barrier layers These factors also help influence the diffusion rate of molecules through the membrane 0 Active transport This type of transport is where molecules are pushed against their concentration gradient Since this process is unnatural it requires energy inputs and proteins to drive the reaction The two types of active transport are 1 and 2 degree transport 0 1st degree transport is where ATP is used directly to power the process o 2ncl degree transport is basically where the disequilibrium created in the first degree transport is utilized to power another process This type of transport basically piggy backs off of 1St degree transport by indirectly using the ATP Importance of Epithelial Membrane The information presented in this section contains information over cell junctions and attachments You can find more in depth information over this concept in my first week of notes for animal phys In terms of the digestive system broken down glucose is diffused through the epithelial tissue and used as a source of energy in the body But just how does glucose diffuse through the tissues Going back to the digestive system more specifically the intestines the apical surfaces of the epithelial tissues are combined via tight junctions These tight junctions form attachments with other epithelial cells to form a type of ring light structure around the lumen cavity of the intestine Glucose cannot pass through tightjunctions so this prevents transcellular transport Instead a glucose molecule must pass through the entire body of the epithelial cell and then diffuse outside This process is done through active transport symporting and sodiumpotassium antiports During both of these transporting processes glucose diffuses into the membrane and then out of the membrane again after traveling across the cytoplasm of the cell Once outside the basal portion of the cellular membrane the glucose diffuses into the capillaries and is transported throughout the rest of the body The body denotes a large majority of energy to power sodiumpotassium pumps These pumps are antiports in which sodium is shipped outside of the cell and potassium is pumped into the cell Naturally there is a high concentration of sodium outside of the cell and a large concentration of potassium inside the cell Because sodium and potassium are being forced against their concentration gradient ATPADPetc is used a fuel source meaning these pumps are of the first degree active transport The interesting thing about this is that a second degree active transport system is used in conjunction with NaK pumps Cells utilize the concentration gradient made in the NaK pump to drive the facilitation of glucose into the cell Since the use of ATP to power the intermembrane proteins that facilitate the diffusion is used in an indirect method this is considered second degree transport
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