Passive Transport

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Passive Transport
Cell Transport
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Transport- Passive or Active

• Passive transport- the movement of materials
  across a cell membrane without the expenditure of
  cell energy
• Active transport- the use of cell energy to move
  materials across a cell membrane (against
  concentration gradient)

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PASSIVE TRANSPORT

• From high to low concentration
• Does not require energy from the cell
• Diffusion
• Osmosis
• Facilitated diffusion

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ACTIVE TRANSPORT

• From low to high concentration
• Requires energy from the cell
• Active transport proteins
• Endocytosis
• Exocytosis

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Types of Membranes

1. Permeable allows all (or most) things to cross
2. Selectively (semi-permeable) membrane allows
   some things to cross but not others (ie. water
   can cross but solutes like salt and sugar can
   NOT)
3. Impermeable membrane does NOT allow anything to
   cross

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Diffusion Osmosis
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DIFFUSION

• The NET movement of particles from an area of
  high concentration of particles to an area of low
  concentration of particles.

Q What is a concentration gradient??
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Dynamic Equilibrium

• At dynamic equilibrium there is no NET (overall)
  movement of particles.
• DYNAMIC implies movement
• EQUILIBRIUM implies a balance
• No longer a concentration gradient
• Particles move equally in all directions

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Dynamic Equilibrium
NOTE At dynamic equilibrium particles are still
moving, its just that overall, they will remain
mixed unless acted upon by another force. (So
no net movement overall).
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Diffusion occurs because particles move DOWN a
concentration gradient.From high to low.
Q How large would the concentration gradient be
at Dynamic Equilibrium?
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Diffusion
Diffusion will always be from an area
of ___________ concentration to an area
of ____________ concentration. It will continue
until _______________ _______________ is
reached.
HIGH
LOW
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Diffusion
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OSMOSIS

• Is special type of diffusion. The diffusion of
  WATER across a semi permeable membrane.

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What is the difference between diffusion and
osmosis?

• Diffusion is the NET movement of particles across
  a semi-permeable membrane from an area of high
  concentration to an area of low concentration.
• Osmosis is the NET movement of water across a
  semi-permeable membrane from an area of high
  water concentration to an area of low water
  concentration.

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Bozeman Podcast

• Cell transport

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What is Facilitated Diffusion?

• Facilitated diffusion (or facilitated transport)
  is a process of diffusion, a form of passive
  transport facilitated by transport proteins.

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Facilitated Diffusion

• The two types of proteins involved in facilitated
  diffusion are
• 1) Channel Proteins (or ion channels)
• 2) Carrier Proteins

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What molecules can pass easily across the cell
membrane?
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SOLUTIONS

1. Hypertonic
2. Hypotonic
3. Isotonic

Solute The substance that dissolves to form a
solution Solvent A substance, usually a
liquid, in which other substances are dissolved
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HYPERTONIC

• solutions are those in which more solute is
  present.
• concentration of dissolved substances is
  higher outside the cell than inside.
• (Water will move OUT OF THE CELL)

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HYPOTONIC

• solutions are those with less solute present.
• concentration of dissolved substances is lower
  outside the cell than inside.
• (Water will move INTO THE CELL)

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ISOTONIC

• solutions have equal (iso-) concentrations of
  dissolved substances. Solute concentrations are
  the same outside the cell and inside.
• (Equal amounts of water movement in and out of
  the cell, with a net flow of zero).

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Animal cell in different solutions
isotonic
hypotonic
hypertonic
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Plant cell in different solutions
isotonic
hypotonic
hypertonic
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Turgor pressure

• The pressure exerted by the cytoplasm (and water
  in the cell) against the non-living cell wall of
  plant cells.