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Movements of substances (Osmosis (What happens to a cell in a solution…
Movements of substances
Diffusion
is a net movement of particles(ions or molecules) from a region where they are of higher concentration to a region where they are of lower concentration,that is,down a concentration gradient.
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The steeper the gradient,the faster the particles will move.This is an important rule:the steeper the concentration gradient for a substance the faster the rate of diffusion is for that substance.
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Key Ideas
The steeper the concentration gradient for a substance,the faster the rate of diffusion.
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Osmosis
The cell surface membrane is a partially permeable membrane.It allows some substances to pass through but not others
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Osmosis is a net movement of water molecules from a solution of higher water potential to a solution of lower water potential,through a partially permeable membrane.
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Hypotonic
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has higher water potential,dilute
Hypertonic solution
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Inside the cell,higher water potential.Outside,lower water potential
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KEY IDEAS
The larger the surface area to volume ratio of a cell,the faster is the rate at which substances move into and out of a cell.
Cells responsible for the absorption of substances are modified to increase the surface area to volume ratio.Such modifications include the long and narrow protrusions of root hair cells;microvilli in epithelial cells in the small intestine;and the flattened biconcave shape of red blood cells.
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Passive, the opposite is active
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