Unit 2.2 Check and Reflect

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Unit 2.2 Check and Reflect

• Target Knowledge
• I can predict the movement of molecules across a
  gradient.
• I know the difference between active and passive
  transport.
• I can describe the cell membrane as a fluid
  mosaic model.
• I can explain semi-permeability.
• Explain the role of macromolecules (lipids and
  protein) in cell transport.
• Target Vocabulary
• cell membrane
• lipid bilayer
• diffusion
• equilibrium
• osmosis
•  

• facilitated diffusion
• active transport
• concentration
• isotonic
• hypotonic

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Cell MembranesOsmosis and Diffusion
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Functions of Membranes

• Protect cell
• Maintain homeostasis
• 3. Selectively permeable - allows some molecules
  in, others are kept out

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Homeostasis

• Balanced internal condition of cells
• Also called equilibrium
• Maintained by cell membrane controlling what
  enters leaves the cell

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Phospholipid Bilayer
Polar heads are hydrophilic water loving
Nonpolar tails are hydrophobic water fearing
Makes membrane Selective in what crosses
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Fluid Mosaic Model Proteins floating in a sea
of lipids
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Proteins Are Critical to Membrane Function
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Blood-Brain Barrier

• Allows some substances into the brain, but
  screens out toxins and bacteria
• Substances allowed to cross include
• water, CO2, Glucose, O2, Amino Acids, Alcohol,
  and antihistamines. HIV and bacterial meningitis
  can cross the barrier.

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Solutions

• Solutions are made of solute and a solvent
• Solvent The liquid part. It does the
  dissolving.
• Solute The thing being dissolved. Salt and
  sugar are solutes.

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Methods of Transport Across Membranes

• 1. Diffusion
• 2. Osmosis
• 3. Facilitated Diffusion
• 4. Active Transport

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Methods of Transport Across Membranes

• 1. Diffusion -passive transport - no energy
  used
• 2. Osmosis - Passive transport of water
  across membrane
• 3. Facilitated Diffusion Needs a helper to get
  things across
• 4. Active Transport- requires energy to
  transport molecules against a concentration
  gradient energy is in the form of ATP

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Diffusion

• Movement of molecules from an area of high
  concentration to an area of low concentration.
• Movement from one side of a membrane to another,
  without help.

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Diffusion
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Diffusion of Liquids
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Diffusion through a Membrane
Solute moves DOWN concentration gradient (HIGH to
LOW)

Cell membrane
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Facilitated Diffusion

• Does NOT require energy
• Uses transport proteins to move things from high
  to low concentration
• Examples Glucose or amino acids moving from
  blood into a cell.

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Facilitated Diffusion
Molecules will randomly move through the pores in
Channel Proteins.
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Facilitated Diffusion

• This is a helper.

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Active Transport

• Requires energy (ATP)
• Moves materials from LOW to HIGH concentration
  AGAINST the concentration gradient.

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Osmosis

• Diffusion of water across a membrane.
• Moves from HIGH water amount (low solute) to LOW
  water amount (high solute).

Diffusion across a membrane
Semipermeable membrane
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You could think of it this way

• In osmosis, water FOLLOWS salt!! This is
  sometimes an easier way to remember this concept.

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Where is the water moving?

• The water is moving out of the cell.
• Why?
• Remember wherever salt is water follows!

Salt
SALT
SALT
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Light blue SaltDark blue water
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There is a lot of salt outside of the cell. What
will happen? Why?
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What will happen if there is a lot of salt inside
of the cell?
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Red Onion Cells

• Normal

• In Salt Water
• What happened to the cytoplasm and cell membrane?

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Diffusion of H2O Across A Membrane
High H2O potential (amount) andLow solute
concentration
Low H2O potential (amount) andHigh solute
concentration
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Osmosis Draw this
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Three Forms of Transport Across the Membrane
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Question

• Why does eating popcorn make you thirsty?
• Popcorn is very salty and may cause water to
  leave the cells of your mouth and through due to
  diffusion. This makes a person thirsty.

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When a sea urchin egg is removed from the ocean
and placed in freshwater, the egg swells and
bursts. Which of these causes water to enter the
egg?

1. Coagulation
2. Sodium Pump
3. Active Transport
4. Osmosis

D
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The picture shows a cell model and the solutions
associated with it. In this situation the cell
model will

1. Gain mass
2. Shrink
3. Increase in solute content
4. Start to vibrate

B
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Which of these best explains why a freshwater
aquarium would be a dangerous habitat for
saltwater fish?
A The tissues of the saltwater fish would absorb
too much acid. B The cells of the saltwater fish
would lose too much water. C The organ systems
of the saltwater fish would consume too much
energy. D The cells of the saltwater fish would
gain too much water.
D
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On a hot summer day, a road-crew worker perspires
and then feels thirsty as her body temperature
increases. This response is an example of

1. Releasing enzymes
2. Maintaining homeostasis
3. Decreasing respiration
4. Assimilating proteins

B
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Think/Pair/Share

• Work with a partner to create different
  situations that can be classified as diffusion.
• Do the same for osmosis.

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Active Transport Video http//www.iteachbio.com/L
ife20Science/LifeFunctionsandTheCell/ActiveTransp
ort.mov
Diffusion Video http//www.iteachbio.com/Life20S
cience/LifeFunctionsandTheCell/Diffusion.mov
Another Video http//www.youtube.com/watch?vML-S
We5bRaE