Lipids and proteins are staple ingredients for membrane

Lipids and proteins are staple ingredients for membrane -...

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Lipids and proteins are staple ingredients for membrane -- along with carbohydrates A phospholipid is an amphipathic molecule: has both hydrophobic and hydrophilic region -- most of the proteins of membranes have both regions Fluid mosaic model: the membrane is a fluid structure with various proteins embedded or attached to a double layer of phospholipids. Membrane is held together by hydrophobic intersections Most of the lipids and some of the proteins can drift laterally driven along cytoskeletal fibers by motor proteins A molecule rarely flip-flops transversely across the membrane Membrane remains fluid as temperature decreases until finally the phospholipids settle into a closely packed arrangement and the membrane solidifies i.e. bacon grease forms lard when it cools the membrane remains fluid to a lower temperature if it is rich in phospholipids with unsaturated hydrocarbon tails because of kinks in tail unsaturated hydrocarbons do not back together closely Integral proteins: penetrate the hydrophobic core of the lipid bilyaer . transmembrane proteins: completely span the membrane Peripheral proteins: are not embedded in the lipid bilayer at all; they are appendages bound loosely to the surface of the membrane On cytoplasmic side of the plasma membrane, some membrane proteins are held in place by attachment to the cytoskeleton On the exterior side, certain membrane proteins are attached to fibers of the extracellular matrix --- these attachments combine to give animal cells a stronger external framework i.e integrins asymmetrical distribution of lipids, carbohydrates, and proteins is determined as the membrane is being built by the ER molecule that start out on the inside face of the ER end up on the outside face of the plasma membrane Cell takes in oxygen for cellular respiration and expels carbon dioxide it also regulates inorganic molecules: Na, K, Ca, Cl Hydrophobic molecules, hydrocarbons, CO2, oxygen, can dissolve in the bilayer However the hydrophobic core of the membrane impedes the transport of ions and polar molecules, which are hydrophilic even water does not easily pass through, nor does glucose and other sugars a charged atom and its surrounding shell of water also cannot easily penetrate
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Protein Transport hydrophilic substances avoid contact with lipid bilayer and pass through transport .Hydrophilic channel acts as tunnel through membrane .physically move molecules through membrane Ex: glucose carried in blood to human liver enters liver cells rapidly through specific transport proteins in the plasma membrane Diffusion: tendency for molecules of any substance to spread out into the available space Concentration gradient: in the absence of other forces, a substance will diffuse from where it is more concentrated to where it is less concentrated Ex: dissolved oxygen diffuses into the cell across the plasma membrane. As long as cellular respiration consumes the oxygen as it enters, diffusion into the cell will
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Lipids and proteins are staple ingredients for membrane -...

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