Lecture 4 10

Lecture 4 10 - Lecture 4 10/05/07 Membrane Transport Where...

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Lecture 4 10/05/07 Membrane Transport Where do membranes come from? Membrane Formatation is lipids made by ER transmembrane proteins Synthesized in smooth endoplasmic reticulum Phospholipids are made by ER transmembrane protein on the cytosolic side of the ER membrane Some are transferred to the lumen side by flippases or scramblases (equilibrate) Cytoplasm gellylike substance Inside of cell where organelles reside Cytosol substance/liquid part of the cytoplasm where organelles are floating in ER and nucleus have continuous membrane allowing for phospholipids and protein diffusion, SER connect to RER, connect to nucleus, perinuclear space connects ER and nucleus lipids travel by diffusion Golgi, Lysosome, Plasma Membrane receive lipids via membrane bound vesicles because they are part of the secretory pathway Mitochondria, plastids, peroxisomes are not attached to secretory pathway use phospholipids exchange proteins – bind to lipid, diffuse away from ER, binds to these Membrane Transport – must get molecules across hydrophobic interior Passive Transport – diffusion, or movement of molecules from areas of high concentration to areas of low concentration without energy required Two kinds of Passive Transport 1.) Simple Diffusion, for molecules o Small in size o Uncharged o Nonpolar -All qualities allow them to go through hydrophobic interior -Examples: oxygen, nitrogen, carbon dioxide (small inert gases) -Water, urea, and glycerol are polar, so they are not able to be diffused as easily 2.) Facilitated Diffusion – for charged or larger molecules, use something else to help them pass through membrane o molecules get through by transmembrane proteins, which have multiple domains that make pores or holes in membrane o Because the molecules are going against a concentration gradient, the transmembrane proteins aid in diffusion both in and out of membrane A. Ion channels- specific for charged molecules to pass through pores formed by transmembrane proteins embedded in the membrane (more efficient than carrier
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Lecture 4 10 - Lecture 4 10/05/07 Membrane Transport Where...

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