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Notes Cell Membrane Diffusion

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Cell Boundaries
The Cell Membrane
The Cell Membrane



Thin, flexible barrier
Regulates what enters and leaves
Protects and supports
aka: Phospholipid Bilayer.
Consists of:
hydrophilic head
(water liking)
and a
hydrophobic tail.
(water avoiding)
Phospholipid Bilayer: Fluid Mosaic Model

Also has




Proteins – doorways
Carbohydrates – name tags
Cholesterol – keeps membrane flexible
Therefore referred to as a “fluid mosaic”
of different molecules.
Cell Boundaries
The Function of the
Plasma Membrane
The Cell Membrane



Cells want nutrients
Cells get rid of wastes
Two ways:


Passive Transport – No Cell Energy (ATP)
needed
Active Transport – Cell Energy (ATP)
required
Passive Transport - Diffusion
Passive Transport – Facilitated
Diffusion
Passive Transport - Osmosis


The diffusion of water molecules
through a cell membrane.
Concentration gradient depends on
amount of dissolved particles (like salt)
inside and outside the cell.
Isotonic Solution

Concentration of a dissolved substance
(solute) is the same inside and outside
the cell.

Isotonic = Dynamic equilibrium.

Cell stays same size.
Isotonic Solution
Hypotonic Solution

Concentration of the solute is low
outside the cell and higher inside the
cell.

Water moves INTO the cell.

Cell gets BIG like the
O in hypOtonic
Hypotonic Solution
Hypertonic Solution


Concentration of the solute is higher
outside the cell and lower inside the
cell.
Water


Exits the cell.
E
Think of the “E” in hyp rtonic
Cell shrinks.
Hypertonic Solution
Assignment


Draw and Label Figure 23, 24 and 25
on page 204-205.
Complete the Osmosis worksheet.
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