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Life Science ch 4a
Membranes 4A
Question | Answer |
---|---|
Unit Membrane | a thin structure composed of proteins and lipids type of membrane found around all cells and around many of the structures inside cells Membranes form the outer boundary of a cell. |
selectively permeable | important property of a unit membrane. Means that certain molecules go through them and other molecules do not |
what easily passes through most membranes | water, oxygen and carbon dioxide |
how does a substance pass through a unit membrane | passive transport or active transport |
what are two main ways of passive transport | diffusion osmosis |
passive transport is | the passage of substances across a membrane without the use of energy |
diffusion | the movement of molecules from an area of higher concentration to an area of lower concentration |
what can accelerate diffusion | heat,movement and pressure |
osmosis is | the diffusion of water through a membrane |
active transport is | the passage of particles through a membrane; requires the use of cellular energy (sometimes because of the size of the molecule being so large, or going against gradient) |
What are some substances that are carried into and out of cells using active transport | calcium, potassium, sodium |