Moving Cellular Materials

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Moving Cellular Materials
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Fluid Mosaic Model

• A mosaic is a structure made up of many
  different parts.
• The plasma membrane of a cell is composed of
  different kinds of macromolecules.

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Phospholipid bilayer
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Passive Transport

• PASSIVE TRANSPORT- DOES NOT require energy to
  move materials through the cell membrane

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3 types of passive transport

• Diffusion
• Facilitated diffusion
• Osmosis

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• 1. DIFFUSION- molecules of a substance will
  move from an area of high concentration to an
  area of low concentration, down the concentration
  gradient, until they reach equilibrium
•  

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• Diffusion occurs in cells when substances
  (O2,CO2, salts, sugars, amino acids) that are
  dissolved in H2O move from an area of higher
  concentration to an area of lower concentration.

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DIFFUSION
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• The rate of difussion will be higher or faster
  when diffusion
• Takes place in gas rather than in liquid
• Takes place at a higher temperature rather than
  at a lower temperature
• Involves small-sized molecules rather than
  larger-sized molecules
• Occurs over a steep concentration gradient

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Facilitated diffusion

• 2. FACILITATED TRANSPORT- requires transport
  proteins in the cell membrane to move materials
  into and out of the cell either because the
  molecules that are transported are too big or
  they are polar (act against the nonpolar fatty
  acid tail of the lipid bilayer)

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FACILITATED TRANSPORT
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• The ability of carrier proteins to change shape
  is regulated by the binding and the release of
  the transported molecules.
• Just like an enzyme that is specific for its
  substrate, a carrier protein is specific for the
  solute it transports but don not catalyse
  chemical reactions.

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Factors that effect diffusion

• Temperature The rate of diffusion increases
  with the increase of temperature
• Pressure- when pressure increases the rate of
  diffusion increases
• Concentration the rate of diffusion is effected
  by the concentration of the substances. It always
  takes place from higher to lower concentration.

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Your opinion

• Why is the rate of diffusion
• Faster in gas than in liquid?
• Faster when temperature rises?
• Faster for small molecules compared to large
  molecules?

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• A) The rate of diffusion is faster in gas because
  there is more space between molecules in a gas
  than in a liquid. Therefore, molecular collisions
  that can slow down movement of molecules occur
  less frequently in gaseous phase than in liquid.

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• B) Increase in temperature increases the rate of
  diffusion because heat energy gained is converted
  into kinetic energy for more rapid random
  movement of molecules.
• C) At the same temperature, smaller molecules can
  move faster than bigger molecules.

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Application of Diffusion

• Exchange of gases between alveoli in the lungs
  and blood
• Exchange of gases between leaf and atmosphere
• Absorption of mineral by root hair cells
• Exchange of gases by all living cells with the
  surrounding.
• And many more!

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Osmosis

• 3. OSMOSIS (diffusion of water)-the movement of
  water molecules through a semi-permeable membrane
  from an area of greater water concentration or
  pressure to an area of lesser water concentration
  or pressure down the concentration gradient

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OSMOSIS
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3 Types of concentration involved in osmosis

• Hypertonic- too much solute, not enough water if
  a cell is placed in this solution, cell will
  shrink wrinkle
• Hypotonic- too much water, not enough solute if
  a cell is placed in this solution, cell will
  swell up, expand
• Isotonic- equal parts water and solute water
  moves in out of the cell in dynamic equilibrium

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OSMOSIS
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3 Types of Passive Transport OSMOSIS
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Application of Osmosis

• Intake of water by root hairs and all other
  cells.

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WAIT!
How Cells Deal with Osmosis?
How Plant Deal with Osmosis?
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Cells Deal with Osmosis

• Some animals are only single celled organisms
  like the paramecium.
• The paramecium is a freshwater pond dweller.
• These paramecia are functioning in a hypotonic
  environment all the time so water is constantly
  diffusing into the organism.
• Paramecia have contractile vacuoles that remove
  excess water from their bodies.
• Sometimes when too much water is added, cells
  burst and this is called cytolysis.

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Plant Deal with Osmosis

• Since plants have a cell wall, osmosis affects
  them differently.
• When osmosis moves water into plant cells, the
  cell membrane swells but stops against the strong
  cell wall.
• This is called turgor pressure.
• When plants dont receive enough water,
  plasmolysis occurs which makes the plants wilt.
• The cell membrane shrinks away from the cell
  wall.

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Thank You!