Ch05_Lecture

Ch05_Lecture - 5 The Dynamic Cell Membrane 5 The Dynamic...

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5 The Dynamic Cell Membrane
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5 The Dynamic Cell Membrane 5.1 What Is the Structure of a Biological Membrane? 5.2 How Is the Plasma Membrane Involved in Cell Adhesion and Recognition? 5.3 What Are the Passive Processes of Membrane Transport? 5.4 How Do Substances Cross Membranes Against a Concentration Gradient? 5.5 How Do Large Molecules Enter and Leave a Cell? 5.6 What Are Some Other Functions of Membranes?
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5.1 What Is the Structure of a Biological Membrane? The general structure of membranes is know as the fluid mosaic model . The phospholipid bilayer is like a “lake” in which a variety of proteins “float.”
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Figure 5.1 The Fluid Mosaic Model
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Figure 3.20 Phospholipids (A) Repeat Fig 3.20A here
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Figure 5.2 A Phospholipid Bilayer Separates Two Aqueous Regions
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5.1 What Is the Structure of a Biological Membrane? Artificial bilayers can be made in the laboratory. Lipids maintain a bilayer organization spontaneously—helps membranes fuse during phagocytosis, vesicle formation, etc.
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5.1 What Is the Structure of a Biological Membrane? Membranes may vary in lipid composition Phospholipids vary—fatty acid chain length, degree of saturation, phosphate groups Membranes may be up to 25 percent cholesterol
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5.1 What Is the Structure of a Biological Membrane? Phospholipid bilayer is flexible, and the interior is fluid, allowing lateral movement of molecules. Fluidity depends on temperature and lipid composition.
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5.1 What Is the Structure of a Biological Membrane? Membranes contain proteins, the number of proteins varies with cell function Some membrane proteins extend across the lipid bilayer—with hydrophobic and hydrophilic regions or domains .
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5.1 What Is the Structure of a Biological Membrane? The proteins and lipids in the membrane are independent and only interact noncovalently.
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5.1 What Is the Structure of a Biological Membrane? Two types of membrane proteins: Integral membrane proteins span the bilayer, hydrophilic ends protrude on either side. Peripheral membrane proteins do not penetrate the bilayer.
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Figure 5.4 Interactions of Integral Membrane Proteins
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5.1 What Is the Structure of a Biological Membrane? Transmembrane proteins may have different domains on either side of the membrane. The two sides of the membrane can have very different properties.
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5.1 What Is the Structure of a Biological Membrane? Some membrane proteins can move freely within the bilayer, while some are anchored to a specific region. Some can be anchored by cytoskeleton elements, or lipid rafts —lipids in semisolid state.
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Membranes are dynamic and are
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Ch05_Lecture - 5 The Dynamic Cell Membrane 5 The Dynamic...

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