1.3 & 1.4 Cellular
Membranes
• What do you know?
• What questions do you
have?
Read & Consider 1.3.1 – 1.3.3
Cells are surrounded
by water inside and
out. Membrane
behavior is dictated by
interactions with
water.
• Polar
• Nonpolar
The diagram should
include:
 Phospholipid bilayer
 Cholesterol
 Glycoproteins
 Integral proteins
 Peripheral proteins
academic.brooklyn.cuny.edu
 Watch – History of Cell Membrane up to Gorter and
Grendel’s 1925 discovery
“Insights into cell membranes via dish detergent”
 Davson and Danielli’s “Fat Sandwich Model” – accepted
until 1972
 Singer and Nicolson’s “Fluid Mosaic Model” – accepted
today
• What do you know?
• What questions do you have?
• Compare and contrast diffusion and osmosis.
Read & Consider 1.4.1-1.4.2
Diffusion: passive movement of particles from a
region of high concentration to a region of
low concentration.
Osmosis: passive movement of water
molecules from a region of lower solute
concentration to a region of higher
concentration.
Isite.lps.org
Simple Diffusion –there is no expenditure of
energy in moving the molecules across the
membrane.
Facilitated Diffusion – larger
molecules move passively
through the membrane via
channel proteins.
sjcabiology.wikispaces.com
Kenpitts.net
Video
Molecules moving from low to high
concentration must be actively moved.
A transport mechanism for the movement of
large quantities.
Exocytosis: vesicle membrane fuses with the
plasma membrane.
Endocytosis: a vesicle is formed by the in
folding of the plasma membrane.
Material Transport
o Phospholipid molecules can change places in
the horizontal plane (creates fluidity).
o Molecule exchange in the vertical plane DOES
NOT occur (maintains integrity).
Video
Inner Life of a Cell
2007 – the President and Fellows of Harvard College
Tissue or organs to be used in medical procedures must be bathed
in a solution with the same osmolarity as the cytoplasm to prevent
osmosis. Complete the exploration phase for the lab with the
following aim:
To determine the osmolarity of an unknown
substance by bathing samples in hypotonic and
hypertonic solutions.