Lecture4_Membrane Transport-2.pptx

Lecture4_Membrane Transport-2.pptx - Chapter 6 Lipids...

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Chapter 6 Lipids, Membranes, and the First Cells
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Reminders and Important Info Your first homework assignment is due Sunday night, so don’t forget to do it. The first quiz is coming up next week on Wednesday. The worksheet that accompanies today’s lecture will be due on Monday.
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Membrane Proteins Phospholipids aren’t the only thing found in cell membranes, proteins are also present.
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Membrane Proteins Proteins that are amphipathic can be inserted into lipid bilayers.
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Membrane Proteins Because of the variability in secondary and tertiary structures, proteins can form channels or pores across the lipid bilayer.
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Membrane Proteins However, it wasn’t always known that proteins could span the membrane. It was originally thought that hydrophilic proteins sandwiched the lipid bilayer.
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Membrane Proteins The fluid-mosaic model states that membranes are a mosaic of phospholipids and different types of protein, with an overall structure that was dynamic and fluid.
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Membrane Proteins As you can see, some proteins span the membrane and have segments that face both the interior and exterior surfaces of the cell. These are known as integral membrane proteins (also known as transmembrane proteins).
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Membrane Proteins Other proteins bind to the membrane without passing through it and are call peripheral membrane proteins. Some peripheral proteins are restricted to one side of the cell or the other, making the sides different from one another.
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Membrane Proteins As you might remember from our previous discussions, ions almost never cross pure phospholipid bilayers on their own.
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Membrane Proteins Ions can cross membranes through specialized membrane proteins called ion channels.
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