+
February 7, 2014
 Objective:
 To
create a model of the cell membrane
 To explain the structure of the cell
membrane
 Journal: What
does it mean to have a phobia
of something? What is an example of a
phobia?
+
Key Terms
What
do you think are the
definitions of the following words?
Hydrophobic
Hydrophilic
+
Key Terms Defined
 Hydrophobic:
 Literally
means fear of water
 Molecules that are hydrophobic repel
water and try to stay away from water
 Hydrophilic:
Literally means water loving
 Molecules that are hydrophilic are
attracted to water and tend to be found
next to water

+
Phospholipids
 The
structure of the phospholipid molecule
generally consists of two hydrophobic tails
and a hydrophilic head.
+
Phosphate Head
 Hydrophilic
 Polar
(has a charge)
 Made
of phosphate
+
Two Fatty Acid Tails
 Hydrophobic
 Nonpolar
 Made
(doesn’t have a charge)
of fatty acids
+
Structure of the Cell Membrane
Phospholipids
make up the cell
membrane of cells.
+
Phospholipid Cell Membrane Activity
 Both
inside and outside the cell contain
water, so how do you think phospholipids
are arranged to make a cell membrane?
 Keep
in mind that phospholipids contain
hydrophilic heads and hydrophobic tails.
+ Cell Membrane Structure
 Phospholipids
form a double
layer called a Phospholipid
Bilayer with the phosphate
groups on the outside and
the fatty acid tails in the
middle
 This
happens because there
is water inside and outside of
the cell, so the water loving
phosphate end is always by
the water
+
Structure Determines Function
 The cell
membrane structure helps it regulate what
can and cannot pass through the phospholipid
bilayer
+
Selectively Permeable
 The cell
membrane is selectively permeable,
meaning that not everything can go across it.
 Only certain things can get into the cell and
only certain things can leave the cell
+
What can pass through the membrane?
 This allows only small,
nonpolar substances to
pass directly through the phospholipid bilayer
 All
other substances are repelled by the
nonpolar fatty acids, so they cannot go directly
through the phospholipid bilayer
+
Other Ways to Pass Through the
Phospholipid Bilayer
 The
cell needs to let other things in and out
of the cell so it uses membrane proteins to
allow specific substances across the
membrane at specific times
 Membrane
proteins can be found on top of
or within the phospholipid bilayer
 http://www.youtube.com/watch?v=LKN5sq5d
tW4
+
Types of Membrane Proteins
+ Receptor Proteins
 Found
on the outside of your
cells
 Enable a cell
to sense its
surroundings by binding
substances outside the cell
 Allows the cell to react to its
surroundings
Cell-Surface
Proteins
+
 Similar to a
nametag
 Protein attached
to a chain of carbohydrates attached to
the cell membrane used to identify each type of cell
+
Transport Proteins
 Allows certain
necessary substances that cannot
pass through the cell membrane into and out of
the cell
+
Transport Proteins
 Channel
Proteins: Serve as a tunnel through
the lipid bilayer that allow SPECIFIC ions,
sugars, and amino acids to pass through the
membrane
 Ex: The channel for sodium ions does not
allow sugars to pass through
+
Transport Proteins
 Carrier
Proteins: Only transport substances that fit
within their binding site through the cell membrane
 Carrier protein binds to a specific substance on one
side of the cell membrane, changes shape and allows
the substance out on the other side of the cell
membrane
+
Daily Activities
 Day
1 – Egg Lab
 Begin
Cell Membrane Model
 Homework:
 Cell
Membrane Labeling Worksheet
+
February 7, 2014
 Objectives:
 To
differentiate between osmosis and diffusion
 To describe how molecules can move down a
concentration gradient
 Journal:
 What
do you think the following words mean?
 Equal
 Concentration
 Diffuse
 If the Monksville dam broke, what would happen
to the water in the Monksville Reservoir?
+
Cell Transport
+
Passive Transport Vocabulary
 Equilibrium:
when there is an equal number of
molecules on both sides of the cell membrane
 Concentration:
the amount of a particular
substance in a given volume
 Concentration
Gradient: When there is a higher
concentration of a substance on one side than the
other
 Diffusion:
When a substance moves from an area
of higher concentration to an area of lower
concentration
+
Types of Transport
 Passive
Transport: does not require energy to
move substances across the cell membrane
 Active
Transport: requires energy to move
substances across the cell membrane
+
Passive Transport
 When
substances enter or leave the cell by
diffusing across the cell membrane down their
concentration gradient
 The
direction the substances move depends on
the concentration gradient
+
Types of Passive Transport
 Simple
Diffusion
 Facilitated
 Osmosis
Diffusion
+
Simple Diffusion
 When
small, nonpolar (uncharged) substances
pass directly through the phospholipid bilayer
from an area of higher concentration to an area
of lower concentration
 Ex:
If there is more oxygen outside the cell than
inside the cell, it will diffuse across the lipid
bilayer and into the cell.
+
+ Facilitated Diffusion
 Substances
that cannot pass directly through
the membrane are helped to diffuse through the
membrane using transport proteins
+
Osmosis
 Facilitated
diffusion of water
from an area of higher
concentration to an area of
lower concentration
 Allows
the cell to maintain
water balance as their
environment changes
+
Water Channels
 Since
water is a polar substance, it does not
directly diffuse across the cell membrane
 So
the cell has specific protein channels that
only allow water to pass through called
aquaporins
+
Predicting Water Movement
 The
direction the water moves depends on the
concentration of the cell’s environment
+
Hypertonic
 Water
moves out of the cell
 There
is more solute outside the cell than
inside the cell
 The
cell loses water and shrinks
+
Hypotonic
 Water
moves in
 There
is more solute inside the cell than
outside the cell
 Cell
gains water and expands
+
Isotonic
 There
is the same concentration of water inside
the cell and outside the cell
 Equilibrium
 Cell
is reached
stays the same size
+
Daily Activities
 Egg
Lab Day 2 – Place eggs in various
solutions
 Finish
Cell Membrane Model
+
February 11, 2014
 Objectives:
 To
differentiate active transport from active
transport
 To describe how active transport moves
molecules
 Journal:
 How
is active different than passive?
+
Active Transport
 Transport
of substances against their
concentration gradients
 Requires
energy usually in the form of ATP
+ Use of Carrier Proteins as Pumps
 Carrier
proteins require energy to pump
substances across their concentration gradient
+
Sodium-Potassium Pump
 Sodium
ions inside the cell bind to the carrier
protein which changes shape and releases sodium
ions outside the cell membrane
 As
a result a phosphate group is released from the
pump, returning the channel protein to its original
shape, and releasing potassium ions inside the cell
 For
every three sodium ions pumped out, two
potassium ions are brought inside
 This
prevents sodium from building up inside the
cell, which would cause the cell to burst due to
osmosis bringing in too much water
+
Vesicles
 Large
substances are too big to cross the
membrane in channel proteins so they use
vesicles
 Vesicle
membranes are lipid bilayer, so they
can bud off from the cell membrane or fuse
with it to move large substances in or out of the
cell
+
Endocytosis
 The
movement of large substances into a cell
using a vesicle
 The
cell membrane forms a pouch around the
substance that closes and then pinches off
inside the cell
 Pinocytosis: also known as cellular drinking,
engulfing liquid particles
 Phagocytosis: engulfing solid particles
+
Exocytosis
 The
movement of large substances out of a cell
using a vesicle
 Vesicles
inside the cell fuse with the cell
membrane and are released outside the cell
 Used
to transport proteins modified by the
Golgi apparatus, excrete wastes, or remove
bacteria
+
Daily Activities
 Day
3 – Finish Egg Lab