Bio I
Rupp
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Why do cells transport materials?
What are the two main methods of cell
transport and how do they differ?
What are homeostasis and equilibrium?
What do the terms isotonic, hypertonic, and
hypotonic mean? Be able to sketch the
scenarios.
PASSIVE TRANSPORT
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No energy needed
Particles move from high
concentration to low
concentration
ACTIVE TRANSPORT
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Energy needed
Particles move from low
concentration to high
concentration
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Diffusion
Osmosis
Facilitated diffusion
Diffusion through ion channels
Wastes Out
Nutrients In
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Diffusion animation
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Simplest type of passive
transport
High to low movement
Difference in
concentration across a
space is the
concentration gradient
Example: sugar cube in a
beaker
Water molecules are in
constant motion and
cause the diffusion
Particles want to reach
a state of equilibrium
 Homeostasis—stable
internal conditions of
living things
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Diffusion of water from
a high concentration to
a low concentration
 Only WATER!!!!
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Osmosis animation
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Isotonic—the concentrations of solute inside
and outside a cell are equal
Hypertonic—the concentration of solute
molecules is higher outside the cell
Hypotonic—the concentration of solute
molecules is lower outside the cell
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Root cells of plants are
surrounded by water—a
hypotonic environment
Water moves into the
plant
The plant cells swell and
push against the cell
walls
The pressure on the cell
wall is turgor pressure
Turgor pressure stops
plants from wilting
PLASMOLYSIS
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Due to hypertonic
environment
Water leaves the cell
Cell shrivels
CYTOLYSIS
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Due to hypotonic
environment
Water enters the cell
Cell swells
Diffusion of large
molecules across a cell
membrane
 Large molecules are
helped across by
channel proteins
 Still passive, therefore;
high concentration to
low concentration
 Facilitated diffusion
animation
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Charged particles,
ions, are moved from
high concentration to
low concentration
 Why can’t ions diffuse
directly through the
membrane?—think
about the cell
membrane
phospholipid bilayer!!
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Sodium-Potassium pumps
Endocytosis
 Pinocytosis
 Phagocytosis
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Exocytosis
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Many cells need higher
concentrations of
sodium outside the cell
and higher
concentrations of
potassium inside the cell
From low concentration
to high concentration
Energy needed in the
form of ATP
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Sodium-potassium pump
animation
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Endo means in and cyto
refers to a cell, therefore;
this is cells ingesting
materials
Pinocytosis—ingestion of
fluids—cell drinking
Phagosytosis—ingestion
of solid molecules—cell
eating—phagocytes and
lysosomes
Endocytosis animation
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Reverse of endocytosis
Waste removal process