Knowra Cell membrane Cell membrane A thin, selectively permeable boundary surrounding a cell, made mainly of lipids and proteins. It regulates exchange with the cell’s environment and supports communication and organization.
Phospholipid bilayer : A double layer of phospholipids whose water-attracting heads face outward and water-repelling tails face inward. This lipid arrangement forms the membrane’s basic selectively permeable barrier.
Phospholipid : A lipid molecule with a phosphate-containing, water-attracting head and two water-repelling fatty-acid tails. Phospholipids spontaneously arrange into the bilayer that forms the membrane’s foundation.
Action potential : A rapid, temporary change in a cell’s membrane potential that propagates along an excitable cell. Nerve and muscle cells use controlled ion movement across their membranes to generate this signal.
Cell wall : A rigid extracellular layer that supports and protects many cells, including those of plants, fungi, and bacteria. Unlike the cell membrane, the cell wall is a supportive outer layer rather than the cell’s selectively permeable boundary.
Membrane proteins : Proteins embedded in or attached to membranes that transport substances, receive signals, or perform other functions. These proteins let selected molecules cross and connect outside signals to cellular responses.
Cholesterol : A sterol lipid found in animal cell membranes that influences their fluidity and permeability. Cholesterol adjusts how tightly neighboring membrane lipids pack together.
Osmosis : The net movement of water across a selectively permeable membrane toward a region of higher solute concentration. Water crossing cell membranes can change cell volume and help regulate internal conditions.
Nuclear envelope : A double membrane surrounding the nucleus of eukaryotic cells, perforated by nuclear pores. It is a specialized membrane boundary that regulates exchange between the nucleus and cytoplasm.
Membrane transport : The movement of substances across a biological membrane by passive or energy-dependent processes. Transport mechanisms turn the membrane’s barrier into a controlled exchange surface.
Glycolipid : A lipid with a covalently attached carbohydrate, commonly found on the outer surface of cell membranes. Its exposed carbohydrate contributes to cell recognition and interactions at the membrane surface.
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