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Moving Materials into and out of the Cell
• Cells need to receive materials:
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water
nutrients
oxygen for the mitochondria
carbon dioxide for chloroplasts
• Cells need to dispose of materials
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carbon dioxide from the mitochondria
other wastes resulting from cellular metabolism
excess water ( especially cells that live in fresh water)
• There are two ways in which cells
receive and dispose of materials:
• Passive transport
• Active transport
• Passive transport:
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does not require an input of energy
• Active transport:
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requires an input of energy
• There
are two kinds of passive
transport:
• diffusion
• osmosis
• Diffusion: the random movement of
molecules from areas of higher
concentration to areas of lower
concentration
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Basically molecules tend to move from where they are more
crowded to where they are less crowded. They do this
because of their own kinetic energy and random movement.
• Osmosis: the diffusion of water through
a membrane
• Osmosis is just a special kind of diffusion. Like regular
diffusion, the water molecules tend to move from where they
are more crowded to where they are less crowded. It has a
special name because of the importance of water to living
cells.
• In order to understand diffusion and
osmosis, it is necessary to understand
solutions.
• Solution: a type of mixture in which one
or more substances are dissolved in
another substance
• Examples of solutions
• salt water
• pancake syrup
• cola
• air
• A solution includes at least one solvent
and at least one solute. Salt water is a
solution, in which salt is the solute and
water is the solvent.
• Solute: the dissolved substance
• Solvent: the substance in which the
solute is dissolved
• Solution: the solvent plus the solute
• The solvent and the solute are not
chemically bonded to each other. The
solvent and solute each have their own
molecules which can be separated
without using any chemical reactions.
• Cells placed in solutions:
• If a cell is placed in a solution, the
solution may be hypertonic, hypotonic,
or isotonic to the cell.
• Hypertonic Solutions
• If the solution is hypertonic to the cell,
there is a higher percentage of solute in
the solution than in the cell.
• This also means that there is a higher
percentage of water in the cell than
there is in the solution.
• Notice that the water(solvent) is the
opposite of the solute. If you have more
dissolved stuff, you have less water and
vice versa.
• So ......, if you place a cell such as an
egg in a hypertonic solution, will water
go out of the egg or into the egg?
• Hypotonic Solutions:
• If the solution is hypotonic to
a cell
such as an egg, it means that there is
a lower percentage of solute in the
solution than there is in the egg.
• This means that there is a higher
percentage of water in the solution
than in the egg.
• So ....., will more water move into the
egg or out of the egg?
• Isotonic Solutions:
• If a cell is placed in an isotonic solution,
the percentage of solute outside the cell
is the same as the percentage of solute
inside the cell.
• This means that the percentage of
water(solvent) is also the same on the
inside as the outside.
• So ....., if you place an egg in an
isotonic solution and check the mass
the next day, what result could you
expect?
• Identify each of the following as
hypertonic, hypotonic, or isotonic to the
egg:
• Vinegar:
• Pancake syrup:
• Distilled water:
• www.youtube.com/watch?v=AYNwynwa
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