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Biology 3rd Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Date: October 5, 2007
Drill

What did the onion cell do when it was exposed to salt water? It shriveled upo Why did it do this? Because the water was at a lower concentration outside the cell
o Draw a picture illustrating what happened.
 What did the onion cell salt water do when it was exposed to DI water? It expanded back
o Why did it do this?
o Draw a picture illustrating what happened.
Selectively Permeable Membrane- Membrane which allows some things to pass through but not all.
Selective Permeable: a cell permits only certain substances-mainly oxygen, water, and food molecules to diffuse into the cell.
Passive Transport: no energy required
Diffusion- Movement of molecules from higher concentration to areas of lower concentration
Diffusion: Molecules moving from high concentration to a low concentration
movement from a high concentration to a low concentration until equilibrium is met
Molecule Movement: temp up molecules move faster, cold temperature the molecules move slower.
Concentration gradient The relation of two given areas, where the concentration of a particular substance differs
between those areas. Diffusion will result in this substance moving along a concentration gradient until the
concentration of the two areas becomes equal.
This movement of concentration along a gradient is common in many biological processes, which are elaborated upon
in the cell biology tutorial involving the biological cell which mentions the various ways how substances can pass
through a cell membrane.
http://www.northland.cc.mn.us/biology/Biology1111/animations/transport1.html
Good site for active and passive transport demonstration
H
L
-Concentration=# of molecules in an area
-Equilibrium=an even amount of molecules
dye in water
Biology 3rd Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
high concentration
movement
low concentration
Movement of molecules is random
*
Motion creates uniform distributions
*
Molecules move from regions of high concentration to low concentration
*
Molecules will passively move "down" a concentration gradient
OsmosisDiffusion of water across a membrane.
Never totally a full equilibrium
4) Osmosis -diffusion of water

the flow of a solvent by diffusion through a semi-permeable membrane from a more concentrated solution to a less
concentrated one, until the concentrations are equalized. It is a major factor in

Brownian Movement:



random movement of molecules or particles
Solids: tight
Liquids: a little spread out
Biology 3rd Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
 Gases: very spread out
Movement of the balloon around the room to represent an atom
•
•
•
1.
Hypertonic- Having a higher solute concentration
Hypotonic- Having a lower solute concentration
Homeostasis- Cell and it’s surroundings are at equilibrium
V.
Hypertonic, Hypotonic, Isotonic
Hypertonic Solution
i. Solute concentration in the environment is higher than that in the cell
VI.
In this diagram, the solution on the left side of the membrane has a higher solute concentration than the solution on
the right side of the membrane. The solution on the left is said to be hypertonic compared to the one on the right.
The higher solute concentration on the left reduces the flow of water molecules from left to right, causing a net flow
of water from the right to the left. If the right side represented a cell placed in a hypertonic solution, water would
leave the cell causing it to dehydrate and collapse.
2.
HYPOTONIC SOLUTION
a. Solute concentration in the environment is lower than in the cell
In this diagram the solution on the left side of the membrane has a lower solute concentration than the solution on
the right side of the membrane. The solution on the left is said to be hypotonic compared to the one on the right.
The lower solute concentration on the left allows for increased flow of water molecules from left to right, causing a
net flow of water from the left to the right. If the right side represented a cell placed in a hypotonic solution, water
would enter the cell causing it to swell and perhaps burst.
3. Isotonic Solution
a. A Solute CONENTRATION IN THE ENVIRONMENT THAT IS EQUAL TO THAT IN THE CELL.
Biology 3rd Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
An isotonic cellular environment occurs when an equal solute concentration exists inside and outside the cell. Molecules flow in
and out at an equal rate by osmosis, causing the cell size to stay the same. It will not lose or gain any solutes. Plant cells in an
isotonic environment are flaccid (they lack firmness) and they will wither. The equilibrium of water movement is unable to provide
plant cells with internal pressure for structural support.
An isotonic solution has an equal amount of dissolved solute in it compared to the things around it. Typically in humans and most
other mammals, the isotonic solution is 0.9 weight percent (0.009 g/ml) salt in aqueous solution, this is also known as saline, which
is generally administered via an intra-venous drip. It is a medium between hypotonic and hypertonic solutions.
http://en.wikipedia.org/wiki/Isotonic
Because the solute concentrations are the same on both sides of the membrane, water molecules move through the
membrane equally well in both directions. There is no net flow of water in either direction.
Osmosis: A special type of diffusion in which water moves from High to Low through a
membrane. A semipermeable or differentially permeable membrane allows water or
other small molecules to pass through because the openings in the membrane are of the proper
size. If the molecules, like starches and proteins, are too large, they can't pass through.
Label the fluid compartments of the following Red Blood Cells and watery environments. Use the
terms:
Hypotonic- Higher concentration of water, lower concentration of dissolved substances (solutes).
Hypertonic- Higher concentration of dissolved substances, lower concentration of water.
Isotonic- Equal effective concentration of water and solutes inside and outside the cell
Salty & Fresh water fish
Freshy is hypertonic
Salty is hypotonic –swelling up
III.
Parts of a Solution
a. Solute =item being dissolved
b. Solvent=item doing the dissolving
c. Solution=solvent + solute
Passive transport-no energy required by the cell
Diffusion fueled by Brownian Motion
Active Transport- Transport, which requires energy (ATP) to take place
Biology 3rd Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher
Factors which control what crosses the cell membrane
1. hydrophobic/Hydrophilic
2. too big-polysaccharides, big lipids, big proteins
Facilitated Diffusion-Diffusion with the help of carrier molecules
Endocytosis
pinocytosis- cell drinking
Phygocytosis-cell eating
Exocytosis=using energy to remove items from the cell (cell vomiting) a vesicle out of the cell
membrance
i. Golgi Apparatus
http://bio.winona.msus.edu/bates/chapter3.htm
Biology 3rd Block Room 128
Mr. R. Bair Biology Teacher
Mrs. MV Smith Resource Teacher