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12 Cards in this Set
- Front
- Back
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Active Processes
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• Two types of active processes:
• Active transport • Vesicular transport • Both use ATP to move solutes across a living plasma membrane |
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Active Transport
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• Requires carrier proteins (solute pumps)
• Moves solutes against a concentration gradient • Types of active transport: • Primary active transport • Secondary active transport |
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Primary Active Transport
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• Energy from hydrolysis of ATP causes shape change in transport protein so that bound solutes (ions) are “pumped” across the membrane
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Primary Active Transport
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• Sodium-potassium pump (Na+-K+ ATPase)
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Vesicular Transport
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• Transport of large particles, macromolecules, and fluids across plasma membranes
• Requires cellular energy |
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Vesicular Transport
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• Exocytosis—transport out of cell
• Endocytosis—transport into cell • Transcytosis—transport into, across, and then out of cell |
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Endocytosis
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• Phagocytosis—pseudopods engulf solids and bring them into cell’s interior
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Endocytosis
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• Fluid-phase endocytosis (pinocytosis
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Endocytosis
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• Receptor-mediated endocytosis
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Exocytosis
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• Hormone secretion
• Neurotransmitter release • Mucus secretion • Ejection of wastes |
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Membrane Potential
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Separation of oppositely charged particles (ions) across a membrane creates a membrane potential (potential energy measured as voltage)
• Resting membrane potential (RMP): Voltage measured in resting state in all cells • Ranges from –50 to –100 mV in different cells • Results from diffusion and active transport of ions (mainly K+) |
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Roles of Membrane Receptors
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• Contact signaling—touching and recognition of cells; e.g., in normal development and immunity
• Chemical signaling—interaction between receptors and ligands (neurotransmitters, hormones and paracrines) to alter activity of cell proteins (e.g., enzymes or chemically gated ion channels) • G protein–linked receptors—ligand binding activates a G protein, affecting an ion channel or enzyme or causing the release of an internal second messenger, such as cyclic AMP |
