Chapter 5: Cellular Membranes CHAPTER 5 Cellular Membranes
Chapter 5: Cellular Membranes Membrane Composition and Structure Membrane Composition and Structure Cell Adhesion Cell Adhesion Passive Processes of Membrane Transport Passive Processes of Membrane Transport Active Transport Active Transport
Chapter 5: Cellular Membranes Endocytosis and Exocytosis Endocytosis and Exocytosis Membranes Are Not Simply Barriers Membranes Are Not Simply Barriers Membranes Are Dynamic Membranes Are Dynamic
Chapter 5: Cellular Membranes Membrane Composition and Structure Biological membranes consist of lipids, proteins, and carbohydrates.Biological membranes consist of lipids, proteins, and carbohydrates. The fluid mosaic model describes a phospholipid bilayer in which membrane proteins move laterally within the membrane.The fluid mosaic model describes a phospholipid bilayer in which membrane proteins move laterally within the membrane. Review Figures 5.1,
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Chapter 5: Cellular Membranes Membrane Composition and Structure Integral membrane proteins are partially inserted into the phospholipid bilayer. Peripheral proteins attach to its surface by ionic bonds. Review Figure
Chapter 5: Cellular Membranes Membrane Composition and Structure The two surfaces of a membrane may have different properties due to different phospholipid compositions, exposed integral membrane proteins, and peripheral membrane proteins.The two surfaces of a membrane may have different properties due to different phospholipid compositions, exposed integral membrane proteins, and peripheral membrane proteins. Defined regions of a plasma membrane may have different membrane proteins.Defined regions of a plasma membrane may have different membrane proteins. Review Figures 5.1,
Chapter 5: Cellular Membranes Membrane Composition and Structure Carbohydrates attached to proteins or phospholipids project from the external surface of the plasma membrane and function as recognition signals between cells. Review Figure
Chapter 5: Cellular Membranes Cell Adhesion In an organism or tissue, cells recognize and bind to each other by means of membrane proteins protruding from the cell surface.In an organism or tissue, cells recognize and bind to each other by means of membrane proteins protruding from the cell surface. Review Figure
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Chapter 5: Cellular Membranes Cell Adhesion Tight junctions prevent passage of molecules through space around cells, and define functional regions of the plasma membrane by restricting migration of membrane proteins over the cell surface. Desmosomes allow cells to adhere strongly to one another. Gap junctions provide channels for chemical and electrical communication between cells. Review Figure
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Chapter 5: Cellular Membranes Passive Processes of Membrane Transport Substances can diffuse passively across a membrane by:Substances can diffuse passively across a membrane by: unaided diffusion through the phospholipid bilayer unaided diffusion through the phospholipid bilayer facilitated diffusion through protein channels facilitated diffusion through protein channels carrier proteins. carrier proteins. Review Table
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Chapter 5: Cellular Membranes Passive Processes of Membrane Transport Solutes diffuse across a membrane from a region with a greater solute concentration to a region of lesser. Equilibrium is reached when the concentrations are identical on both sides. Review Figure
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Chapter 5: Cellular Membranes Passive Processes of Membrane Transport The rate of simple diffusion of a solute across a membrane is directly proportional to the concentration gradient across the membrane.The rate of simple diffusion of a solute across a membrane is directly proportional to the concentration gradient across the membrane. A related important factor is the lipid solubility of the solute.A related important factor is the lipid solubility of the solute. 19
Chapter 5: Cellular Membranes Passive Processes of Membrane Transport In osmosis, water diffuses from regions of higher water concentration to regions of lower concentration across a membrane. 20
Chapter 5: Cellular Membranes Passive Processes of Membrane Transport In hypotonic solutions, cells tend to take up water while in hypertonic solutions, they tend to lose it. Animal cells must remain isotonic to the environment to prevent destructive loss or gain of water. Review Figure
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Chapter 5: Cellular Membranes Passive Processes of Membrane Transport The cell walls of plants and some other organisms prevent cells from bursting under hypotonic conditions.The cell walls of plants and some other organisms prevent cells from bursting under hypotonic conditions. Turgor pressure develops under these conditions and keeps plants upright and stretches the cell wall during cell growth.Turgor pressure develops under these conditions and keeps plants upright and stretches the cell wall during cell growth. Review Figure
Chapter 5: Cellular Membranes Passive Processes of Membrane Transport Channel proteins and carrier proteins function in facilitated diffusion. Review Figures 5.9,
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Chapter 5: Cellular Membranes Passive Processes of Membrane Transport The rate of carrier-mediated facilitated diffusion is at maximum when solute concentration saturates the carrier proteins so that no rate increase is observed with further solute concentration increase. 27
Chapter 5: Cellular Membranes Active Transport Active transport requires energy to move substances across a membrane against a concentration gradient.Active transport requires energy to move substances across a membrane against a concentration gradient. Review Table
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Chapter 5: Cellular Membranes Active Transport Active transport proteins may be uniports, symports, or antiports. Review Figure
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Chapter 5: Cellular Membranes Active Transport In primary active transport, energy from the hydrolysis of ATP is used to move ions into or out of cells against their concentration gradients. Review Figure 5.12 & Table
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Chapter 5: Cellular Membranes Active Transport Secondary active transport couples the passive movement of one solute with its concentration gradient to the movement of another solute against its concentration gradient.Secondary active transport couples the passive movement of one solute with its concentration gradient to the movement of another solute against its concentration gradient. Energy from ATP is used indirectly to establish the concentration gradient resulting in movement of the first solute.Energy from ATP is used indirectly to establish the concentration gradient resulting in movement of the first solute. Review Figure
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Chapter 5: Cellular Membranes Endocytosis and Exocytosis Endocytosis transports macromolecules, large particles, and small cells into eukaryotic cells by means of engulfment and by vesicle formation from the plasma membrane.Endocytosis transports macromolecules, large particles, and small cells into eukaryotic cells by means of engulfment and by vesicle formation from the plasma membrane. Review Figures
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Chapter 5: Cellular Membranes Endocytosis and Exocytosis In receptor-mediated endocytosis, a specific membrane receptor binds to a particular macromolecule. 38
Chapter 5: Cellular Membranes Endocytosis and Exocytosis In exocytosis, materials in vesicles are secreted from the cell when the vesicles fuse with the plasma membrane. Review Figure 5.14 again
Chapter 5: Cellular Membranes Membranes Are Not Simply Barriers Membranes function as sites for recognition and initial processing of extracellular signals, for energy transformations, and for organizing chemical reactions.Membranes function as sites for recognition and initial processing of extracellular signals, for energy transformations, and for organizing chemical reactions. Review Figure
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Chapter 5: Cellular Membranes Membranes Are Dynamic Although not all cellular membranes are identical, ordered modifications in membrane composition accompany the conversions of one type of membrane into another type.Although not all cellular membranes are identical, ordered modifications in membrane composition accompany the conversions of one type of membrane into another type. Review Figure
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