Membranes
Homework
Objectives
Be able to calculate a solution’s
concentration
Identify solutions as being hypertonic,
hypotonic, or isotonic
Learn how osmosis works
Study!
Key concepts so far this unit. If you can’t explain these
things, you need to study:
– How to recognize a lipid
– What shape a phospholipid is
– Hydrophilic vs hydrophobic, and which part of the phospholipid is
which
– Why phospholipids form a phospholipid bilayer, and which parts
are on the inside vs outside of the bilayer
– Why diffusion happens the way that it does
– The difference between simple and faciliated diffusion
Egg Lab
QuickTime™ and a
decompressor
are needed to see this picture.
Solutions
• Solution: a mixture of a solute dissolved
in a solvent.
• When talking about concentration on either
side of a membrane, we have names for
types of solutions.
Solutions
• Latin/Greek Parts Sheet out:
• Hyper
• Hypo
• Iso
Solutions
• Hypertonic: more concentrated than
the other solution
• Hypotonic: less concentrated than the
other solution
• Isotonic: equally concentrated as the
other solution
Solution Concentrations
• Concentration is not about the amount
of stuff. It’s like density: all about the
comparison between amounts.
• Concentration is written as amount of
solute divided by amount of solvent.
(Solute/Solvent.)
• What units do you think we would use for
it?
Solution Concentration
• Get one whiteboard per table!
• If I have 5 salt molecules and 5 water
molecules, what is the concentration?
• Show the math, and draw a diagram.
Solution Concentration
• If I have 1 g of salt and 1 mL of water,
what’s the concentration?
• Math and diagram
Solution Concentration
• If I have 100000 g of salt and 100000
mL of water, what’s the concentration?
• Math, and your diagram can be imprecise
Solution Concentration
• Which is more concentrated?
• 4 g of solute in 2 mL of solvent
• 400 g of solute in 400 mL of solvent
Solutions
1. If I have a solution that’s 5 g/mL on
Side A of a membrane and 10 g/mL
on Side B, what do we call the two
sides?
2. 50 g/mL on Side A and 100 g/mL on
Side B?
3. 6 g/mL on Side A and 6 g/mL on Side
B?
Solutions
1. If I have 5 salt molecules and 15
water molecules on Side A, and 10
salt molecules and 15 water molecules
on Side B, what do I call the two
sides?
2. Side A: 5 salt, 5 water. Side B: 5 salt,
5 water.
3. Side A: 10 salt, 5 water. Side B: 50
salt, 50 water.
Osmosis
• String = cell membrane.
• Left side = in cell, right side = outside.
• Popcorn = water. Water CAN diffuse
across the plasma membrane.
• Stones = solute, like salt or sugar. It
CANNOT diffuse across the plasma
membrane.
Osmosis
• Osmosis = the diffusion of water across
a selectively permeable membrane.
QuickTime™ and a
decompressor
are needed to see this picture.
Osmosis
• Each table, take a whiteboard,
whiteboard marker, and eraser.
• Use X for solute (like salt), O for solvent
(water).
Osmosis
• Divide the board as shown, drawing in
the table.
• Draw a diagram of a cell in a hypertonic
solution, and fill in the first part of the
table.
Osmosis
• Now draw what happens to that cell.
Fill in the rest of the table.
Osmosis
• Draw a diagram of a cell in an isotonic
solution.
Osmosis
• Draw a diagram of a cell in hypotonic
solution. Don’t erase it when you’re
done.
Osmosis
• Draw another diagram next to or below
it, showing what will have happened to
the cell because it was placed in that
hypotonic solution.
Osmosis
• If I put a cell in a hypertonic solution,
will the cell swell, shrivel, or stay the
same?
Osmosis
• Draw two diagrams, a before and an
after, showing what happens when you
put a red blood cell in a hypertonic
solution.
Osmosis
• Draw two diagrams, a before and an
after, showing what happens when you
put a red blood cell in a hypotonic
solution.
Osmosis
• What kinds of solutions were the red
blood cells in A, B, and C placed in?
QuickTime™ and a
decompressor
are needed to see this picture.
Osmosis
• A salt water fish, used to living in ocean
waters with high salt concentrations, is
mistakenly placed in a fresh water
aquarium. Draw two diagrams showing
what happens to the fish’s cells.
Osmosis
• Sprinkling salt on a leech or slug’s wet
skin causes serious damage to the poor
animal. Draw diagrams of a slug’s cell
showing why.
Osmosis
1. Sprinkling salt on a leech or
slug’s wet skin causes serious
damage to the poor animal.
Use osmosis to explain why.
2. Have your notebook and
macromolecule table ready.
Today’s Agenda
Active Transport
Finish Lipids part of macromolecule
table
Review
Osmosis
• http://highered.mcgrawhill.com/sites/0072495855/student_vie
w0/chapter2/animation__how_osmosis_
works.html
QuickTime™ and a
decompressor
are needed to see this picture.
Cell Membrane
• So we’ve seen 3 ways of moving stuff in
and out of a cell. Remind me what they
are:
• Simple Diffusion =
• Facilitated Diffusion =
• Osmosis =
Active Transport
• Active Transport = using proteins embedded
in the cell membrane to move things in or out
of the cell, costing the cell energy.
• Active Transport is exactly what it sounds like: the
cell actively pulls stuff in or kicks stuff out.
• http://www.youtube.com/watch?v=STzOiRqzzL4
Getting In/Getting Out
• Divide a piece of paper into four quadrants.
• In each quadrant, draw a labeled diagram or
image of the four ways that things move in
and out of cells.
• Beneath the drawing, briefly define or explain
the process.
• Check with a classmate if you’re not sure
you’ve done it right.
Quiz
• NOT BEING GRADED. This is just for
you and I to see how well you
understand what we’ve done so far.
• Take out a piece of paper, write your
name, put away your notes.
Egg Lab Report
Homework
 Egg Lab Due 10/26
 Test on Membranes & Diffusion coming
up
 Reminder: Virus Brochures due 11/13
Egg Lab
 GET MY HELP
 This is a chance for me to help you see the
level of writing I expect
 Use the checklist to be sure you’re including
everything
 Complete paragraphs. You don’t have to talk
about the topics in my order, put them in an
order that makes sense in the paragraph.
CONNECT THE IDEAS.