뒤로Anatomy & Physiology: Cell Membrane Structure and Transport
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Plasma membrane: flexible outer boundary, Cytoplasm: intracellular fluid with organelles, Nucleus: DNA-containing control center.
A fluid mosaic model with a bilayer of phospholipids and embedded proteins, including cholesterol for stiffness.
Phosphate heads are polar and hydrophilic, fatty acid tails are nonpolar and hydrophobic.
Functions include transport (channels/carriers), enzymes, receptors, motor proteins, and cell-to-cell connections.
Allows nutrients in, wastes out, and prevents many undesirable substances from entering due to its hydrophobic core.
Movement of nonpolar, lipid-soluble substances like oxygen and carbon dioxide directly through the lipid bilayer down their concentration gradient.
Passive transport of hydrophobic molecules with help from carrier or channel proteins down their concentration gradient.
Specific molecules bind to transmembrane carriers which change shape to transport them across the membrane.
Transmembrane proteins with aqueous cores that allow ions to pass based on size and charge; can be leakage or gated channels.
Movement of water through a selectively permeable membrane via aquaporins, from low to high solute concentration.
Isotonic: normal shape, Hypertonic: cell shrinks (crenation), Hypotonic: cell swells and may burst (lysis).
Active transport requires ATP energy to move solutes against their concentration gradient (low to high).
Pumps 3 Na+ out and 2 K+ in using ATP, maintaining electrochemical gradients in excitable cells.
Uses energy stored in ion gradients created by primary active transport to move other solutes indirectly.
Movement of large substances across membranes inside vesicles, requiring ATP; includes endocytosis, exocytosis, and transcytosis.
Phagocytosis (cell eating), Pinocytosis (cell drinking), and Receptor-mediated endocytosis (selective uptake).
Cell forms pseudopods to engulf solid particles into a vesicle called a phagosome, used by macrophages.
Non-specific uptake of extracellular fluid and solutes by plasma membrane infolding; no receptors involved.
Selective uptake where substances bind to specific membrane receptors before vesicle formation.
Process where vesicles fuse with the plasma membrane to eject substances like hormones and neurotransmitters out of the cell.