Topic 2: Cells


1.3 & 1.4 Cellular


• 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

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.

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.

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).


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.