MOVEMENT ACROSS CELL
MEMBRANES
Biology 9B - Dickson
Bio 9B: Friday, 12/9/11
Title: Movement Across Cell Membranes
Homework: None – have a great weekend!
Silent Do Now (in NB w/ date & title)
 What is the difference between “regular” diffusion and
facilitated diffusion?
 What do you think the cell membrane is made of?
 What does it mean for the membrane to be “selectively
permeable?
 What is one thing you learned from doing the StarLogo
computer lab?
Today’s Objectives


Describe how the structure of the membrane helps it to
function
Describe and explain the following terms:






Lipid Bilayer
Selective Permeability
Diffusion
Osmosis
Facilitated Diffusion
Active Transport
Agenda:
 Notes/Discussion
 Exit Ticket and Hand Back Work / Grades
Cell Membrane Structure
The cell membrane is made of…
 Lipid Bilayer
 Two
layers of lipids that form the
outer membrane of a cell.
 Flexible
 Strong
 Do

not Dissolve in water
Proteins in the lipid bilayer
 Help
transport molecules across the
membrane
Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Cell Membrane Function

Selective Permeability
 When
a membrane only allows
certain substances to pass across
the membrane (and not others)
 Based on the size, shape, and
charge (+/-/neutral) of the
substances
Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Methods for Materials to Enter/Leave the Cell
Diffusion

Diffusion
Movement of molecules from a
high concentration (more stuff) to low
concentration (less stuff)
 Spreading out so all areas have an
equal concentration


Osmosis
Osmosis

Diffusion of water through a
selectively permeable membrane
Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Methods for Materials to Enter/Leave the Cell

Facilitated Diffusion
 When
a substance diffuses through a
membrane by going through a protein
channel

Regular diffusion goes through the
lipid bilayer
Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Methods for Materials to Enter/Leave the Cell

Active Transport
When a substance is pumped across a
membrane from where there’s a low
concentration to where there’s a high
concentration (against the concentration
gradient)
 Opposite of diffusion
 Requires a pump (made of protein) and ATP
energy!

Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Bio 9B: Monday, 12/12/11
Title: Diffusion Lab
Homework:
Complete pages 3 and 5 of the lab packet.
 Silent Do Now:

Complete the worksheet.

Today’s Goals: You will be able to:
Form a well-reasoned hypothesis about diffusion across
membranes.
Test this hypothesis by following a lab procedure to perform
an experiment
Create a data table in order to organize and record your
results.
Lab:
Diffusion Across Cell Membranes
Model Cell
w/ Dialysis
Tubing
Membrane
Water
Objectives for Class:
 Design an experiment by drawing from your knowledge of starch, glucose, cell membranes, and
experimental indicators that test for the presence of starch and glucose.
Diffusion Lab:
Procedure Review – Part 1

Set-up Dialysis Bag





Rinse w/ tap water to wash excess
solution from outside of bag
Set-up Beaker



Moisten tube and tie one end
Add the starch & glucose solution to the
tube
Tie the top of the tube
Fill a 250 ml beaker ¾ of the way with
water
Add Iodine to water – mixture should be
orange
Put dialysis bag into beaker with water
Water and Iodine
and iodine
Objectives for Class:
 Design an experiment by drawing from your knowledge of starch, glucose, cell membranes, and
experimental indicators that test for the presence of starch and glucose.
Diffusion Lab:
Procedure Review – Part 3

Starch

How do we test for it?


How do we know starch has passed through
membrane?


Use Iodine
Iodine outside the dialysis bag turns from yellow-orange to
purplish- brown
Glucose

How do we test for it?


Boil it in Benedicts solution or use a glucose test strip
How do we know glucose has passed through the
membrane?

Glucose test strip will change color
Objectives for Class:
 Design an experiment by drawing from your knowledge of starch, glucose, cell membranes, and
experimental indicators that test for the presence of starch and glucose.
Expectations for Lab Work





Stay at your own table (no wandering)
Talk quietly with members of your own group
Stay focused on the lab!
Follow every step of the procedure
Stay safe – use materials as instructed, no messing
around
New Vocabulary
Diffusion, Osmosis and Selective Permeability In Action:
http://zoology.okstate.edu/zoo_lrc/biol1114/tutorials/Flash/Osmosis_Animation.htm
Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Bio 9B: Thursday 12/15/11
Title: Diffusion Lab – Analysis & Conclusions
Homework:
Read pages 956-960. Answer questions on the back of
the assignment sheet (write answers in notebook)
Silent Do Now (in notebook w/ title & date)
 Copy the table on the board into your notebook.
Make it huge (fill the whole page of your notebook).
 Fill in the first column (Results) by filling in each box with…
 Was

there a color change? If so, describe!
Take out your lab packet and check your data table on
page 4 if you can’t remember the results.
Today’s Objectives & Agenda:
You will be able to:








Explain the results of the diffusion experiment
Use the lab report rubric to identify mediocre versus
excellent examples of Background Info sections
Write or improve your own Background Info, Analysis, and
Conclusion sections of your lab report
Agenda:
Class Discussion of Results, Analysis, and Conclusions
Evaluate examples of Background Info
Class discussion & brainstorm for this lab’s Background Info
Time to type! And also to conference w/ Ms. Dickson about
past assignments.
Diffusion Across Cell Membranes:
Presenting the Data/ Results

Color Change?
Glucose Test Strip
changed color
Bag Turned
Purple/ Black
No Color Change to the Water
Water and Iodine
Objectives for Class:
 Use scientific vocabulary to explain how a cell membrane controls what enters and leaves a cell
Diffusion Lab: Analysis & Conclusions
RESULTS –
Was there a
color change?
Describe!
Dialysis
Bag
Turned from white
to purple
Water in
Beaker
Glucose
Test Strip
No change
(stayed orange)
Turned from
green to browngreen
ANALYSIS –
What does this
mean?
CONCLUSIONS
Why did this
happen? Does
it support our
hypothesis?
Today’s Objectives & Agenda








Discuss and analyze the results of the diffusion
experiment
Use the lab report rubric to identify mediocre versus
excellent examples of Background Info sections
Identify the strengths and areas for improvement in
your own background info section
Agenda:
Quick Class Discussion of Results
Evaluate examples of Background Info
Class discussion & brainstorm
Peer editing
Lab: Diffusion Across Cell Membranes
Writing Better Background Information Sections
Task 1 – Do this silently on your own:
• Read the two example Background Information
sections from the Denatured Enzyme Lab
• Grade them according to the rubric.
• Identify strengths and areas for improvement
Objectives for Class:
Use the lab report rubric to identify mediocre versus excellent
examples of Background Info sections
Sample Background Info sections
Example 1
Example 2
Strengths:
Contains scientific terms and
definitions
Things to improve:
Unclear definitions
Missing connections
Awkward wording
Topic sentence
Overall grade: Fair
Strengths:
State purpose
Explains all terms
Good connections & examples
“Because…”
“However…”
Things to improve:
Add more vocabulary
Overall grade: Excellent
Objectives for Class:
Use the lab report rubric to identify mediocre versus excellent examples of Background Info sections
Diffusion Lab Background Info
Turn your lab packet to page 5
 Your Tasks in A Small Group:
1.
Make sure everyone has descriptions of each word
2.
Make sure everyone has descriptions of two more words
3.
Fill in the Connections part for each word by writing how it
relates to at least one other word, or to the experiment
4.
At the bottom of that page, brainstorm some topic sentences
to start off your Background paragraph
5.
Number each term in the chart based on the order you think
you should introduce it in your Background paragraph
Your goal as a group is to help EVERYONE be ready to write an
excellent Background Info paragraph!

Quiet Independent Work Time
Tasks to Work On:
Continue writing your lab report (it is due Monday)
Do tonight’s HW (book reading & questions)
Conference w/ Dickson about past assignments or help on
the lab report
Small groups will come to work w/ Dickson on the Do Now
from earlier this week
Work quietly and professionally Stay focused on biology.
No internet – it slows down everyone’s laptop!
Bio 9B: Friday12/16/11
Title: Cell Membrane Vocabulary Application
Homework:
Typed & completed lab report due Monday.
Silent Do Now – On an index card, not in your notebook!
 Find the following definitions in your notebook and write
them on an index card (all definitions on same card):
Diffusion
 Osmosis
 Facilitated Diffusion
 Active Transport

Today’s Objective: Apply these vocabulary words to various
situations in living things – so that you can accurately
identify examples and pictures of each process.
Instructions




Spend 3 minutes at each station
Read the scenario, look at the pictures, read the
questions
Mark your answers on the answer sheet (do not
write on the station handouts)
Work with your assigned partner (next slide), talk
quietly on with them, and stay focused on the work.
Partners
Window Side of the Room
Cabinet Side of the Room





Justin—Jarred
Ritshly—Kira
Jenna—Skyeler—Tia
Ronica--Naidaliz
Sequoia—Steven—DJ





Noah—Priscilla
Nicole—Zak—Sara
Destinee—Emily
Aaron—Emperor
Tracey-Natalie-Elizabeth
Exit Ticket


Work silently on your own to correct or finish your
Do Now sheet from Monday
If you don’t get your Do Now sheet back, complete
the AP Biology test questions!