Download CH 2.1 Cell Transportation PowerPoint

Cellular Transport
CH 2.1
Mr. Traub
Osmosis: Diffusion of Water
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Osmosis: diffusion of water across a selectively
permeable membrane depending on the
concentration of solutes on either side of the
membrane
Diffusion: movement of particles from an area
of higher concentration to an area of lower
concentration
Important factor in maintaining homeostasis
Osmosis In Action
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Before Osmosis
After Osmosis
What Just Happened?
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Two solutions separated by a selectively
permeable membrane, only allows water to
diffuse across
Water flows to side of the membrane where
water has low concentration. (High to Low)
Water diffuses until it has equal concentration
on both sides of the membrane
Therefore, an unequal distribution of particles is
called a concentration gradient
How Osmosis Affects Cells
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Most cells, whether in multicellular or unicellular
organisms, are subject to osmosis because they
are surrounded by water solutions.
Three types of solutions that cells may be in;
Isotonic solution
 Hypotonic solution
 Hypertonic solution
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Isotonic Solution
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Solute concentration of solution and water equal to that of cell
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Water molecules move in and out at the same rate, so cell
maintains shape
Hypotonic Solution
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Solute concentration of solution lower than cell
Less dissolved particles outside of cell than inside of cell
More water outside the cell than inside
Hypo = less, under (think hypodermic, hypothermia); Tonic =
dissolved particles
Cell expands (and may burst)
Hypertonic Solution
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Solute concentration of solution higher than cell
More dissolved particles outside of cell than inside of cell
Hyper = more (think hyperactive); Tonic = dissolved particles
Water moves out of cell into solution
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Cell shrinks
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Other Types of Cellular
Transport
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Passive Transport
Active Transport
Passive Transport
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Cell uses no energy to move particles
Transport proteins, carrier proteins, and channel
proteins help substances move through the
plasma membrane
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This is known as Facilitated diffusion
Facilitated Diffusion
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Allows diffusion of large, membrane insoluble compounds such
as sugars and amino acids
Does not require energy (passive)
Highly Selective
Substance binds to membrane-spanning transport protein
Binding alters protein conformation, exposing the other surface
Fully reversible - molecules may enter the cell and leave the cell
through the transport protein.
Particles move from areas of high concentration to areas of low
concentration.
Active Transport
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Move particles from region of lower
concentration to region of higher concentration
Requires energy from the cell
Carrier protein binds with particle of substance
to be transported, chemical energy allows cell to
change shape of carrier protein and particle is
released on other side of membrane
Passive & Active
Transport of Large Particles
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Endocytosis: process by which a cell
surrounds and takes in material from its
environment
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Exocytosis: expulsion of materials from the
cell
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Ex: expel waste, secrete hormones
Endocytosis & Exocytosis
Review
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http://www.wiley.com/legacy/college/boyer/04
70003790/animations/membrane_transport/me
mbrane_transport.htm