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UAB BY 330 - Permeability of plasma membrane
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C. Semipermeablility- movement across membrane1. ‘Micromolecular’ transporta) Water is what cells have to have but it is left to its own devices, paramount and main thing that the cell has to be cognoscente of(1) moves in by diffusion along with small molecules (sometimes simple sugars)(a) diffusion- movement of molecules from high concentration to low concentration(b) the smaller and more non-polar it is (lipid soluble), the more likely the molecule will move in with diffusion(c) Average cost of diffusion = 30% of the cell’s energy is needed to regulate thisb) Carrier-mediated protein – will assist the movement of the molecule in or out of the membrane(1) 3 Classes of carrier proteins(a) uniport – ligand binds to protein and there is a conformational change and the protein will send that one molecule in one direction.(b) Symport- movement two molecules one direction, mostly in the glucosal epithelia ( best example is glucose/sodium symport)(c) antiport –movement of 2 molecules in 2 different directions (best example is the Na/K ATPase pump move Na out and K in)(2) All 3 can use energy or may not need energy, sometimes called Facilitated diffusion.(3) *carriers can move against the gradient, physically binds to the molecule and moves it acrossc) Some proteins do not bind to the molecule to help it across: Called Channels(1) sometimes have a protein which looks like it is sown through the membrane like a button hole and it allows very specific molecules to go through(2) have a domain that serves as a gate, and is called a gated channel(a) gated channels are closed until they are told to open(3) Types:(a) Ligand gated channel- most channels are specific for ions and to open it, some other signaling molecule will bind to the outer part of the domain and the binding will cause it to change its shape according to the signal(i) gated channels allow ions through baised on diffusion, which is based on concentration amounts(ii) glutamate is an example for what might be used as a ligand gate(b) voltage-gated- far more common in muscles and nerve cells, ion channels that respond to changes in voltage differences(i) usually, there is a negative charge inside the cell and a positive charge outside the cell(ii) example = action potentential that depolarizes the cell and the voltage gated channels are opened and closed(4) *cannot move molecules against the gradient- just opening a gate so they can go through or notd) Huge Difference between enzymes and transporters, enzymes convert to product and transporters just take molecules across it(1) movement by diffusion doesn’t hit Vmax(2) movement by transporter proteins will hit Vmax and move across faster in the beginning2. Macromolecular transporta) endocytosis – movement of large molecules or groups of molecules into the cell(1) the membrane invaginates around the molecule or group, and overtime that membrane will completely surround and then pinch and completely enclose the vesicle(2) the endocytose vesicle (endosome) will then separate the plasma membrane and leave it intact(3) phosphotidycholine is on the cytoplasmic monolayer, the outer monolayer of the plasma membrane and that becomes the inner monolayer of the endosome(4) Types(a) pinocytosis- small amount of molecules brought through (amino acids and simple sugars)(b) phagocytosis- brings in bigger molecules to the cell (proteins etc.)(5) **endocytosing ALL THE TIME(6) **Any surface of the plasma membrane can take in molecules(7) Receptor mediated endocytosis- ** different from regular exocytosis because a receptor is required, need very specific molecules- this endosome made is very important and needs to be protected --clathrin(a) example – need cholesterol, essential in the body:(b) LDL is group of protein that surrounds about 15 different molecules of cholesterol- then the cell will put a signal or a receptor in the membrane, specific for the molecule it wants, like LDL – triggers an endocytosis of the cell(c) endosomes are coated when invagination is happening, it is a trimeric protein, 180 micrometers called clathrin(trimer found free in the cytoplasm) and when the receptor signals it, it will bind together and form a clatherine ‘honey-comb’ type coat (mail of sorts) during the invagination processb) exocytosis- movement of molecules outside the cell(1) endosome brought to the membrane(2) fuses with plasma membrane, evaginates, and the membrane of endosome becomes part of plasma membrane(3) **Only exocytose when necessary(4) ** Normally only exocytose in the membrane where there is high calcium and is close to the Golgi Apparatusc) bulk transport- endocytosis on one side of cell and moves straight through the cell, then exocytosis on the other side of those cells(1) often used in capillary beds, where it allows molecules to go through and get to the capillaries on the other side of the celld) regulation of endo and exocytosis(1) important for keeping plasma membrane balanced(a) diet= endocytose more(b) lazy/overeat= exocytose more(2) need to balance the cell nutrientse) actin microfilaments bind to the plasma membrane and help to pull the vesicle (endosome) in a specific direction(1) process of the endosome movement is part of the cytoskeleton, the actin microfilaments of the cellBY 116 1st Edition Lecture 15 Outline of Last Lecture II. Plasma membraneA. A lot more internal membrane than plasma membraneB. Structure Outline of Current Lecture C. Semipermeability of membraneCurrent LectureC. Semipermeablility- movement across membrane 1. ‘Micromolecular’ transport a) Water is what cells have to have but it is left to its own devices, paramount and main thing that the cell has to be cognoscente of (1) moves in by diffusion along with small molecules (sometimes simple sugars) (a) diffusion- movement of molecules from high concentration to low concentration(b) the smaller and more non-polar it is (lipid soluble), the more likely the molecule will move in with diffusion(c) Average cost of diffusion = 30% of the cell’s energy is needed to regulate thisb) Carrier-mediated protein – will assist the movement of the molecule in or out of the membrane(1) 3 Classes of carrier proteins(a) uniport – ligand binds to protein and there is a conformational change and the protein will send that one molecule in one direction.These notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as


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UAB BY 330 - Permeability of plasma membrane

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