BackAnatomy & Physiology: Cells and Membrane Transport
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Terms in this set (28)
Cell theory states that a cell is the structural and functional unit of life, all cells arise from preexisting cells, and the organism's function depends on the activities of its cells.
The three basic parts are: plasma membrane (flexible outer boundary), cytoplasm (intracellular fluid with organelles), and nucleus (DNA-containing control center).
Extracellular materials include extracellular fluids (interstitial fluid, blood plasma, cerebrospinal fluid), cellular secretions (e.g., saliva, mucus), and extracellular matrix (substance holding cells together).
The plasma membrane is a phospholipid bilayer with embedded proteins that acts as a selective barrier controlling entry and exit of substances, maintaining the cell's internal environment.
The lipid bilayer consists of 75% phospholipids (polar hydrophilic heads and nonpolar hydrophobic tails), 5% glycolipids (lipids with sugar groups), and 20% cholesterol (increases membrane stability).
Integral proteins span the membrane and function as transporters, enzymes, or receptors. Peripheral proteins are loosely attached and function as enzymes, motor proteins, or in cell-to-cell connections.
The glycocalyx is a sugar coating on the cell surface made of glycoproteins and glycolipids that acts as a biological marker for cell recognition and immune system identification of self vs. nonself.
Tight junctions prevent passage between cells; desmosomes provide anchoring and resist tearing; gap junctions allow communication via tunnels for ions and small molecules.
Passive transport requires no energy and includes simple diffusion, facilitated diffusion, and osmosis, all moving substances down their concentration gradients.
Diffusion speed is influenced by concentration gradient, molecular size, and temperature.
Nonpolar, lipid-soluble substances and very small polar molecules like water can pass by simple diffusion.
Facilitated diffusion uses carrier proteins or channel proteins to transport larger or polar molecules down their concentration gradient without energy.
Osmosis is the passive movement of water across a selectively permeable membrane from an area of low solute concentration to high solute concentration.
Osmolarity measures solute particle concentration; as solute concentration increases, water concentration decreases, driving water movement by osmosis.
Tonicity is a solution's ability to change cell shape by altering water volume: isotonic (no change), hypertonic (cell shrinks), hypotonic (cell swells and may lyse).
Active transport uses ATP to move solutes against their concentration gradient when molecules are too large, not lipid soluble, or moving against the gradient.
The Na+-K+ pump actively transports 3 Na+ ions out and 2 K+ ions into the cell, maintaining electrochemical gradients essential for nerve and muscle function.
Secondary active transport uses energy stored in ionic gradients created by primary active transport to move other solutes, often via symporters or antiporters.
Vesicular transport moves large particles or fluids across membranes in vesicles, including endocytosis, exocytosis, transcytosis, and vesicular trafficking, requiring ATP.
Endocytosis types: phagocytosis (cell eating), pinocytosis (cell drinking), and receptor-mediated endocytosis (selective uptake via receptors).
RMP is the electrical potential across the plasma membrane due to separation of charged particles, typically between –50 and –100 mV, with the inside of the cell negative relative to outside.
K+ diffuses out through leakage channels, leaving negative proteins inside, creating a negative charge that pulls K+ back, establishing the RMP.
CAMs anchor cells to each other or the extracellular matrix, assist cell movement, attract white blood cells, and transmit signals for migration and specialization.
The cytoskeleton includes microfilaments (actin strands), intermediate filaments (rope-like fibers), and microtubules (hollow tubes), providing structure and facilitating movement.
Cilia move substances across cell surfaces, flagella propel whole cells, and microvilli increase surface area for absorption.
Rough ER synthesizes proteins for secretion, plasma membrane, or lysosomes, modifying and packaging them for transport.
The Golgi apparatus modifies, sorts, and packages proteins and lipids from the ER for secretion, membrane insertion, or lysosome formation.
Apoptosis is programmed cell death where cells self-destruct neatly via caspase activation, DNA degradation, and phagocytosis, removing damaged or unwanted cells.