Knowra Plasma membrane Plasma membrane The plasma membrane is a selectively permeable lipid bilayer that encloses a cell’s cytoplasm. Its proteins and lipids regulate exchange and interactions with the cell’s surroundings.
Phospholipid bilayer : A double layer of phospholipids with water-attracting heads facing outward and water-repelling tails facing inward. This arrangement forms the membrane’s basic selectively permeable barrier.
Phospholipid : A lipid molecule with a phosphate-containing hydrophilic head and hydrophobic fatty-acid tails. Its amphipathic shape drives spontaneous bilayer formation in water.
Ion channel : A membrane protein that forms a pore through which specific ions move down their electrochemical gradients. Ion channels make membrane electrical signaling possible in nerves and muscles.
Cell wall : A rigid extracellular layer that supports and protects cells in plants, fungi, bacteria, and some other organisms. It lies outside the plasma membrane and provides mechanical support the flexible bilayer cannot.
Membrane protein : A protein embedded in or associated with a biological membrane, where it performs structural, transport, or signaling roles. Membrane proteins provide channels, carriers, receptors, and anchors that lipids alone cannot supply.
Cholesterol : A sterol lipid found in animal cell membranes that influences membrane order and fluidity. It buffers the effects of temperature on the animal plasma membrane’s flexibility.
Aquaporin : A membrane channel protein that selectively facilitates water movement across cell membranes. Aquaporins enable rapid water transport while excluding many dissolved ions.
Nuclear envelope : A double membrane surrounding the eukaryotic cell nucleus, perforated by nuclear pore complexes. It encloses a specific organelle rather than the cell’s entire cytoplasm.
Facilitated diffusion : The passive movement of molecules across a membrane through channels or carriers, down their concentration or electrochemical gradient. It lets selected polar molecules cross without the membrane’s hydrophobic core blocking them.
Glycolipid : A membrane lipid with a carbohydrate group, usually displayed on the extracellular surface of the plasma membrane. Its outward-facing sugars contribute to cell recognition and surface interactions.
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