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Cell Membranes. Structure and Function. Animal Cell Membrane. Semi-permeable Membranes. Lipid membranes are semi-permeable, also called selectively permeable Water moves across the membrane freely Ions (charged particles) do not move across the membrane freely
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Cell Membranes Structure and Function
Semi-permeable Membranes • Lipid membranes are semi-permeable, also called selectively permeable • Water moves across the membrane freely • Ions (charged particles) do not move across the membrane freely • Many large molecules do not move across the membrane freely
Passive Transport • Diffusion – the movement of substances from an area of higher concentration to an area of lower concentration • Osmosis – the movement of water from an area of higher water content to an area of lower water content
Active Transport • The movement of a substance against the concentration gradient (from lower concentration to higher concentration • Active transport requires the use of energy
Membrane proteins play an important role in passive and active transport