Cool Cats Don’t Run
Cool Cats Don’t Run
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DNA 1/27/16
• Take out quiz photo and corrected responses for
acct check.
• Write analogies (like in yesterday’s activity) for
the following organelles. Continue on the same
sheet of paper from yesterday, so they are all in
one place:
1. Ribosome
2. Mitochondria
3. Cell Wall
Nucleus
Nucleolus
(made up of DNA)
Endoplasmic Reticulum
Vacuole
Ribosomes
Mitochondria
Chloroplast
Cell Membrane
Cell Wall
Share with Your Partner
1. What are some things that you bring into
your home because you need them?
2. What are some things that are not wanted in
your home so you keep them out?
3. What are some things that are sent out of
your house?
The Cell Membrane:
The Gatekeeper
of the Cell
What does Alice have to do with Cell Membranes?
Class Brainstorm
What properties could the cell membrane use to distinguish
between molecules?
Physical Properties
Chemical Properties
What is the cell membrane?
• Every cell is
surrounded and
protected by a plasma
membrane (aka cell
membrane)
• The cell membrane is
made mostly of lipids,
carbohydrates, and
some protein channels
What does the cell membrane do?
The cell membrane has two main jobs:
1. It separates the inside of the cell (the
intracellular space) from the outside of the
cell (the extracellular space)
2. It acts as a gatekeeper by only allowing
certain molecules in or out
Components of the Cell Membrane
• The cell membrane is made
of special lipids called
phospholipids
• Phospholipids have two
parts:
–Hydrophilic (waterloving), or polar heads
–Hydrophobic (waterfearing) or nonpolar tails
Drawing out phospholipids
DNA 1/28/16
Draw a phospholipid. Label the two parts of
phospholipids that make up the phospholipid
bilayer.
• Which part of the phospholipid is hydrophobic?
Which part is hydrophilic?
Announcements
• Tomorrow = last day of plant data collection
• Case study paragraphs due tonight at 11:59 PM.
• Plant data section due Tues at beginning of class. (hard copy in class
for peer review. No turnitin submission)
Today!
• There is a hiring symposium that I am sneaking
away to watch. Here is what to do:
• 1. Collect and record plant data.
• 2. Work on case study paragraphs (peer revise all
paragraphs in your group to make sure that the
reasoning makes sense for all 4!! Use the rubric!)
• 3. Make revisions to intro and methods section of
plant lab. (If I have not written your feedback yet,
look at someone’s feedback within your group.
There were a lot of common errors)
Other parts of the cell membrane
• Several types of proteins
are embedded in the cell
membrane.
• Two major ones are:
• Protein channels:
proteins that allow a
passage way into and out
of the cell
• Protein receptors: Binds
to a signaling molecule
outside of the cell that
causes a reaction inside
of the cell
Other parts of the cell membrane
• The cell membrane also
has carbohydrates on the
outer surface that play a
role in cell recognition
and cholesterol around
the lipid tails to regulate
membrane fluidity
Activity: Modeling the Cell Membrane
• Work together with your shoulder partner to make a
model of the cell membrane
• Make sure you READ each step carefully and WORK
together!
Q-tip = Phospholipid
String = carbohydrate
Straw = Protein channel
Cholesterol
Cotton ball = nucleus
Candle = protein receptor
Step 1: Identifying the phospholipid
• First identify which parts of the q-tip are the polar phosphate
head and the nonpolar lipid tail
• Which part does not want to come into contact with water?
Q-tip = Phospholipid
Step 2: Building the cell membrane
• Imagine that the surface of your desk is made up of water.
Arrange your q-tips in a way so that the minimum number of
hydrophobic (nonpolar regions) are exposed to water.
Step 3: Building the cell membrane
• Arrange your q-tips in a way that results in an inner
compartment that can also have water.
Water inside
Step 4: Building the cell membrane
• Add your protein receptor and channels to the membrane to
allow things to communicate and enter/exit the cell.
Straw = Protein channel
Candle = protein receptor
Step 5: Adding cholesterol and carbohydrates
• Snugly pack the cholesterol
strands between the lipid tails.
• These cholesterol molecules help
maintain membrane fluidity
• Add carbohydrates to the outer
layer of phospholipids.
Cholesterol
• These carbohydrates allow the
cells to be recognized by other cells
and molecules (and viruses yikes!)String = carbohydrate
Step 6: Nucleus
• Add your nucleus to the cell.
• Is this cell a eukaryotic or prokaryotic cell? How do you
know?
• What does the nucleus hold in these cells?
Cotton ball = nucleus
Drawing out our cell membrane
What does the cell membrane do?
• The cell membrane helps cells
maintain homeostasis by allowing
SOME things to enter/exit the cell
and not others – it is SEMIPERMEABLE
Questions:
• If ANYTHING could freely move in and out of the membrane, would it still be
called semi-permeable?
• If NOTHING could move in and out of the membrane, would it still be called
semi-permeable?
Semi-permeable
• Semi = Partially
• Permeable = Allowing
things to pass through
• Semi-permeable means
that some things can enter
and leave while other
things cannot