Topic 2: Cells

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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

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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.

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

Molecules moving from low to high concentration must be actively moved.

Video

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.

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