Chapter 6 The Chemistry of Life

1
Chapter 6 The Chemistry of Life 6.2 Water and
Diffusion Review Vocabulary homeostasis
regulation of the internal environment of a cell
or organism to maintain conditions suitable for
life.
2
Water and Its Importance 1. metabolic processes
via ion movement 2. transport of blood, plant
sap, etc. 3. 70 95 of most organisms
3
Water Is Polar What do you think about when you
hear the word polar?
4
When you think of polar as an unequal pull, as in
the polar Earth example, you can get a good idea
of what a polar bond is. A polar molecule is a
molecule with an unequal distribution of charge
that is, each molecule has a positive end and a
negative end. Water is such a molecule.
5
The picture on the left shows why there is an
unequal pull of forces after hydrogen has
bonded with oxygen, there are still 6 non-bonded
electrons available on the oxygen end.
6
Nature often takes advantage of this polar
property of water. For example, plants use
capillary action for water transport from roots
to leaves and certain insects use surface tension
as an advantage for mobility.
7
Also, this polar characteristic of water can
dissolve many ionic and covalent
compounds. Ionic table salt (NaCl), salt
substitute (KCl), and toothpaste, aka stannous
fluoride (SnF2)
8
Covalent table sugar, aka sucrose (C11H22O11),
nitrogen oxide and sulfur dioxide (NOx and SO2),
the two main compounds in acid rain.
9
Water is also attracted to other water molecules
via hydrogen bonds.
10
Water Resists Temperature Changes This fact is
extremely important to life as water functions as
an aqueous environment for all cells. This in
turn helps cells maintain homeostasis.
11
Freezing Water Expands This property helps break
rocks apart over time and helps with the process
of soil formation.
12
Diffusion Defined gradual mixing of molecules of
two or more substances due to random motion.
13
Predict how long it would take for diffusion to
take place if we took a drop of blue food
coloring and placed it in water
14
Brownian Motion In 1827, Scottish scientist
Robert brown used a microscope to observe pollen
grains suspended in water. He noticed the grains
moved constantly in little jerks, as if being
struck by invisible objects.
In 1827, using this single-lens microscope,
Scottish botanist Robert Brown first observed
what came to be called Brownian motion among
grains of pollen from a North American wildflower
suspended in water.
15
For almost 85 years Brownian motion was argued
about but never explained, until in Albert
Einstein's "miraculous year" of 1905 -- the same
year he proposed the special theory of relativity
and the quantum nature of light -- Einstein, who
was only distantly acquainted with Brown's work,
published a theory giving precise formulas for
predicting the behavior of small particles of a
given size suspended in liquid at a given
temperature.
http//www.aip.org/history/einstein/brownian.htm
16
Process of Diffusion The net movement of
particles from an area of higher concentration to
an area of lower concentration is of particular
interest to biologist. Three key factors affect
the rate of this movement 1. concentration 2.
temperature 3. pressure What relationship do
you believe exists between these 3 factors and
the rate?
17
The Results of Diffusion Dynamic equilibrium is
the end result of the process of diffusion. This
occurs when no further change in concentration
will occur, even though there is still random
movement of the particles.
http//www.chemistry.wustl.edu/courses/genchem/Tu
torials/Kidney/diffusion_movie.html
18
(No Transcript)
19
Diffusion in Living Systems
Concentration Gradient is an unequal
distribution of particles. Ions and molecules
within cellular processes move from an area of
higher concentration to an area of lower
concentration. This is know as, moving with the
gradient.
20
(No Transcript)
21
Life would not exist without the process of
diffusion. Each single cells life of each
organism depends on diffusion for movement of
molecules in and out of the cell membrane. This
movement provides the following 1.
nutrition 2. excretion of wastes 3.
homeostasis 4. other metabolic processes such as
gas exchange from bloodstream to lungs
22
(No Transcript)
23
(No Transcript)