Essential Question: How do materials get in and out of a cell?

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Essential Question How do materials get in and
out of a cell?

• You learned in section 1 that the membrane does a
  lot to control what goes in out of the cell.
• Today you will learn the specific ways materials
  enter exit the cell.
• You will see that the way a cell gets each
  material it needs is unique and specialized.
• Also, that there are ways the cell gets its
  needed materials in or out by both using and not
  using energy.

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Objectives Passive Active Transport

• Identify what determines the direction in which
  passive transport occurs.
• Understand osmosis and why its important.
• Illustrate how substances move against a
  concentration gradient in active transport.

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Vocabulary

• Equilibrium
• Concentration gradient
• Diffusion
• Carrier protein
• Osmosis
• Sodium-potassium pump

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Before we get started

• Youll need to know these terms before we begin.
  Define these in your notebooks.
• Solute A solid particle
• Solvent A liquid the dissolves solutes.
• Solution Solute dissolved in a solvent
• Concentration an amount of a substance within a
  given volume

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Passive Transport Diffusion Equilibrium

• In a solution, randomly moving molecules tend to
  fill up a space.
• Watch as I drop some food coloring into the
  beaker.
• What happens?
• The process that causes this dispersion of polar
  color molecules is diffusion.
• When the space is filled evenly with the
  particles, a state called equilibrium is reached.
• A state that exists when the concentration of a
  substance is the same through-out a space.

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Equilibrium
http//highered.mcgraw-hill.com/sites/0072495855/s
tudent_view0/chapter2/animation__how_diffusion_wor
ks.html

• Temperature
• As the ice melts the water temperature drops.
• The low temperature of the ice equalizes with the
  warmer water temp.

Ice Temp
Water temp
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Passive Transport Concentration Gradient

• The amount of a particular substance in a given
  volume is called the concentration of the
  substance.
• When one area has a higher concentration than
  another area does, a concentration gradient
  exists.
• The difference in the concentration of a
  substance across a distance.

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Down CONCENTRATION GRADIENT Up
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Visual Concept Concentration Gradient
Area of High Concentration
Area of Low Concentration
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Passive Transport Diffusion

• The movement of particles from regions of higher
  density to regions of lower density is diffusion.
• Watch as I drop food coloring into the beaker.
• Would you all agree that the concentration of the
  food coloring is highest right where it is
  dropped?
• Over time, the particles of color naturally
  diffuse through the water, without any need of
  physical movement.

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Diffusion
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Visual Concept Diffusion
Area of High Concentration
Area of Low Concentration
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Diffusion or Simple Diffusion

• One of the main jobs of the cell membrane is to
  separate the cytoplasm from the fluid outside the
  cell.
• But the cell still needs an abundance of
  materials that comes from outside the cell.
• Some substances that the cell needs can enter and
  leave the cell by diffusing across the cell
  membrane.
• The direction of movement depends on the
  concentration gradient, meaning that the
  particles will naturally flow where there is less
  of them, usually where more is needed.
• The greatest part of this is
• DIFFUSION DOES NOT REQUIRE ENERGY!

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Diffusion is Passive Transport

• In cells, diffusion through the membrane is
  called passive transport.
• In passive transport, substances cross the cell
  membrane down their concentration gradient.
• Some substances diffuse through the lipid
  bilayer.
• Other substances diffuse through transport
  proteins.

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Small Non-Polar Diffuses directly through
membrane
Small Non-Polar Diffuses directly through
membrane
Large or Polar Cannot diffuse directly through
membrane
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Passive Transport Not So Simple Diffusion

• Facilitated Diffusion
• Facilitate means to help.
• Many ions, large, and polar molecules that are
  important for cell function do not diffuse easily
  through the nonpolar lipid bilayer.
• During facilitated diffusion, transmembrane
  proteins help these substances (large /or polar)
  diffuse through the cell membrane.
• Two types of transport proteins
• channel proteins
• carrier proteins.

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Facilitated Diffusion Passive Transport

• Facilitated Diffusion through Channels
• Ions, sugars, and amino acids can diffuse through
  the cell membrane through channel proteins.
• These proteins, sometimes called pores, serve as
  tunnels through the lipid bilayer.
• Each channel allows the diffusion of specific
  substances that have the right size and charge.

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Passive Transport, Facilitated Diffusion

• Facilitate Diffusion Through Carrier Proteins.
• Carrier proteins transport substances that fit
  within their binding site.
• A protein that transports substances across a
  membrane
• A carrier protein binds to a specific substance
  on one side of the cell membrane. This binding
  causes the protein to change shape.
• As the proteins shape changes, the substance is
  moved across the membrane and is released on the
  other side.

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Visual Concept Passive Transport Facilitated
Diffusion
Link to McGrawHill online (a good textbook) for
animations and explanations of biology
concepts. Take the quizzes! http//highered.mcgra
w-hill.com/sites/0072495855/student_view0/chapter2
/animation__how_diffusion_works.html
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Osmosis.

• Water is essential for our survival. It is a
  critical molecule in the production of ATP.
• (without ATP we die)
• But water is polar cant go directly through
  the lipid bilayer.
• Water gets into the cell via a form of
  facilitated diffusion, called osmosis.
• Water has its own channel protein through which
  it can diffuse.

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Osmosis/ How the Environment Changes
how_osmosis_works.html

• When ions and polar substances dissolve in water,
  they attract and bind some water molecules. The
  remaining water molecules are free to move
  around.
• If a concentration gradient exists across a
  membrane for solutes, a concentration gradient
  also exists across the membrane for free water
  molecules.
• Osmosis occurs as free water molecules move down
  their concentration gradient into the solution
  that has the lower concentration of free water
  molecules.

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Questions on Passive Transport?

• What is a concentration gradient?
• What is diffusion?
• What is passive transport?
• What kinds of passive transport are there?
• Does passive transport use energy?

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Active Transport
Area of High Concentration
Area of Low Concentration
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Active Transport

• The opposite of diffusion is active transport.
• In order to move substances against their
  concentration gradients, cells must use energy.
• Active transport requires energy to move
  substances against their concentration gradients.
• Most often, the energy needed for active
  transport is supplied directly or indirectly by
  ATP.

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Visual Concept Comparing Active and Passive
Transport
Link on sodium potassium pump
NO http--www.stolaf.edu-people-giannini-flashanim
at-transport-secondary20active20transport.swf
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Active Transport, continued

• Pumps
• Pumps are carrier proteins that require energy to
  move substances UP their concentration gradient.
• The sodium-potassium pump is a carrier protein
  that actively transports three sodium ions out of
  the cell and two potassium ions into the cell.
• This pump is one of the most important carrier
  proteins in animal cells. It prevents sodium ions
  from building up in the cell, resulting in
  osmosis into the cell which could burst the
  cell.
• The concentration gradients of sodium ions and
  potassium ions also help transport other
  substances, such as glucose, across the cell
  membrane.

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Sodium-Potassium Pump
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Mass Transport Across a Membrane

• Vesicles
• Many substances, such as proteins,
  polysaccharides, and even bacteria, are too large
  to be transported by carrier proteins altogether.
  
• Instead, they cross the cell membrane in
  vesicles, which are membrane-bound (lipid
  bi-layer) sacs.
• The vesicle membrane is a lipid bilayer, like the
  cell membrane. Therefore, vesicles can bud off
  from the membrane, fuse with it, or fuse with
  other vesicles.

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Mass Transport Across a Membrane

• Vesicles
• Vesicles help the movement of large molecules two
  ways
• Endocytosis
• Exocytosis

http//wps.aw.com/bc_goodenough_boh_4/177/45510/11
650562.cw/index.html
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Endocytosis Into
Cell ingests large macromolecules or other cells
Vesicle
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Exocytosis Exits
Opposite of Endocytosis Release of contents in
the cell to the external environment
Vesicle
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Summary Questions

• Does Passive Transport require Energy?
• Does Active Transport require Energy?
• What is the energy required for Active Transport?
• What is the difference between active and passive
  transport?
• Is diffusion Passive or Active?
• Is Osmosis Passive or Active?
• Is the Sodium-Potassium pump Passive or Active?
• How would these substances get into the cell?
• Oxygen (non-polar)
• Carbon dioxide (non-polar)
• Glucose (a large non-polar substance)
• Ions traveling down their concentration gradient
  (small polar)
• Ions traveling up their concentration gradient
  (small polar)
• Water (small polar molecule)
• Amino acids (large molecules of varying polarity)

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Concept Check
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Summary

• In passive transport, substances cross the cell
  membrane down their concentration gradient.
• Osmosis allows cells to maintain water balance as
  their environment changes.
• Active transport requires energy to move
  substances against their concentration gradients.

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Group Practice

• Get into groups and complete the worksheet. When
  completed, we will cover answers.
• Make sure to use the correct color for each
  molecule.
• At the end of class, turn in
• Your completed Transport Practice Worksheet
• HW If not completed
• The HW from last night.

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Take these Quizzes

• http//www.hbwbiology.net/quizzes/ch8-cell-membran
  e.htm