AIM: How is the structure of the plasma
membrane related to its function?
DO NOW: What are some other names for
the cell membrane?
What does the cell
membrane do?
Functions
Helps to maintain balance or homeostasis
within the cell
Boundary between cell and its
environment
Selectively permeable: allows some to
pass and others are kept out
How is the cell membrane
constructed?
The cell membrane
Plasma membrane
Phospholipid bilayer
2 layers of
phospholipids
– Embedded with
proteins and
cholesterol molecule
Construction of the Cell
Membrane Wisconsin Online
Wednesday
AIM: How is the cell membrane selectively
permeable?
DO NOW: Explain the difference between
hydrophilic heads and hydrophobic tails.
Homework: Textbook read pages 201202. Review figure 7.20 and explain what
is happening. Define dynamic equilibrium
Structure of a phospholipid
Hydrophilic heads:
water loving
– Made up of phosphate
and glycerol
Hydrophobic tails:
do not like water
– Built from long
hydrocarbon fatty acid
tail
Why is it important for the
membrane to be partly
hydrophobic and partly
hydrophilic?
http://www.susanahalpine.co
m/anim/Life/memb.htm
How do membrane proteins and
cholesterol create a fluid
mosaic?
Cell Membrane - Video
Membrane proteins
Peripheral: at the surface of cell
membrane
– Fibrous proteins: receptors
– Glycoproteins: cell to cell recognition or
identification
Integral: occupy the length of the bilayer
– Pore proteins: passive transport
– Channel proteins: active transport
– Ion pumps
Why does the membrane need
cholesterol?
Helps stabilize the membrane
Cholesterol is lipid soluble
How does the structure of the
membrane relate to its function?
Friday 12/7/12
AIM: how does the structure of the cell
membrane relate to its function?
DO NOW: What do you think would
happen to a fresh water fish if you put it in
salt water and explain why you think that
HOMEWORK: Text page 183 questions 13
Fluid Mosaic model
Individual phospholipids
are not bonded
Fluid because
phospholipids move
At the same time,
proteins in the
membrane also move
among the
phospholipids
Proteins, cholesterol
and carbohydrates
create a mosaic model
Explain the difference between
an integral and a peripheral
protein.
Integral proteins are large enough to
span both layers of the phospholipid
bilayer
Peripheral proteins only span one layer
How does the cell membrane
maintain homeostasis?
By regulating and helping molecules enter or
leave the cell
Membrane proteins and hydrophillic heads
help molecules enter and/or leave the cell
Tuesday 12/11/12
AIM: How does the cell membrane
maintain homeostasis?
DO NOW: 1- The cell organelles
crossword puzzle
2- does the cell membrane function the
same in the plant and in the animal cell? If
so what is its function.
HOMEWORK: textbook page 169 and 170
questions 2,4,5,6,8,9,11
The structure of the cell membrane
helps it regulate homeostasis
HOW?
By being selectively permeable
This means it chooses certain molecules
to cross
NOT ALL MOLECULES CAN CROSS
THE CELL MEMBRANE
Use your notes to design a well organized
table using the parts and the functions that
build the plasma membrane
Thursday 12/13/12
AIM:how do molecules move across the
cell membrane?
DO NOW: Explain why the plasma
membrane is called a phospholipid bilayer.
Explain why the plasma membrane is
called a fluid mosaic
HOMEWORK:Text page 191 questions 15
Membrane proteins
Integral
– Carrier protiens
– Channel proteins
Peripheral
– Glycoproteins: part carbohydrate part protein
What are the functions of the Cell
Membrane?
Selective Permeability
Maintain homeostasis
Create a barrier
Structural support
The cell membrane
Regulates homeostasis by controlling
which molecules can enter and/or leave
the cell
Does the cell membrane let
ALL molecules across?
How does the cell membrane
choose which molecules to
cross?
Factors which effect permeability
Size of molecule
Solubility of molecule
– Does it dissolve in water
– Does it dissolve in lipid
Charge on molecule
Concentration gradient: amount or quantity
of molecules on either side of the
membrane
Transport
Passive: molecules move from a high to
low concentration
Active: molecules move from low to high
concentration
Assessment
Explain how concentration gradient is a
driving force of transport
Tuesday 12/18/12 pd 7
AIM: How do molecules move down the
concentration gradient?
DO NOW: 1- Draw the picture below\
2-which direction will molecules move and why?
HOMEWORK: Reading Comprehension handout
Essential Biochemistry Membrane Transport
Slides 1-6
Transport across the membrane
Cytoplasm has different
molecules and ions.
Some easily pass through
the plasma membrane
into the cell.
These include water,
oxygen, carbon dioxide,
glucose and sodium and
chloride ions.
Passive Transport
Small lipid soluble molecules move from a
crowded area to a less crowded area
Down the concentration gradient
No energy is required
Simple Diffusion
Facilitated Diffusion
Osmosis
These include water, oxygen, carbon dioxide,
glucose and sodium and chloride ions.
Passive transport
How do molecules know when to
stop moving?
Dynamic equilibrium: same amount of
molecules on each side of the membrane
Essential Biochemistry Membrane Transport
7-8
Simple Diffusion
Movement is driven
by concentration
gradient
Molecules move from
an area of high
concentration to low
concentration
Solute concentration
is equal
Facilitated diffusion
Some molecules are
too big to simply
diffuse
So they need the help
of carrier proteins
Transport is still
driven by a
concentration
gradient
AIM: Why is osmosis simple diffusion?
DO NOW: Explain why energy is not
needed to move glucose down the
concentration gradient of the cell.
Homework: Reading Comprehension
handout Cell transport: Read pages 111113. answer questions 1-5 on pages 11113. Questions 1-3 on Pages 115-116.
Period 2 Tuesday 12/18/12
AIM: How do water molecules move across the cell
membrane?
DO NOW: The cell transport handout page 111 Reading
toolbox: create a concept map connecting the following
terms: the cell membrane, concentration gradient,
cell transport, the plasma membrane, passive
transport, active transport, down, against,
molecules, move, high, low, ATP, ion pump, the
phospholipid bilayer, energy, simple diffusion,
facilitated diffusion, osmosis, equilibrium, carrier
proteins
HOMEWORK: The cell transport handout page 116
questions 4-6
How is simple diffusion similar from
facilitated diffusion?
Both are examples of Passive transport
So they both move molecules from high to
low concentration
We call that moving down the
concentration gradient
How is simple diffusion similar from
facilitated diffusion?
Both are types of passive transport
So they move molecules down the
concentration gradient
Which means molecules move from high
concentration (a lot) to low concentration (
a little)
How is simple diffusion different
from facilitated diffusion?
Facilitated diffusion uses a membrane
carrier protein
WHY?
Because some molecules are too big to
cross the membrane by itself
Wednesday 12/19/12
AIM: How does solute concentration
regulate osmosis?
DO NOW: 1- Take out your handout
2- explain the similarities between osmosis
and simple diffusion.
HOMEWORK: Read page 180. Explain
what happens to Red blood cells in
hypertonic, hypotonic and isotonic
environments
Simple diffusion and osmosis
Both move molecules from high to low
concentrations
DO NOT NEED ENERGY
Types of passive transport
Differences between simple
diffusion and osmosis
Osmosis is the simple diffusion of water
molecules ONLY
Simple diffusion moves small molecules
like oxygen and ions
The cell membrane is selectively
permeable
That means it picks and chooses which
molecules can cross
Osmosis
Simple diffusion of
water
Water molecules
move from a
concentrated area to
a less concentrated
area
Solute; dissolved
molecule
– Glucose, salt, ions
Activity
On a clean sheet of loose leaf, list and
briefly describe the similarities and
differences of each type of passive
transport.
Osmosis.mp4 - YouTube
Tonicity
Refers to the solute concentration on
either side of the cell membrane
Measures how many solute molecules are
dissolved inside of the cell and out side of
the cell
Isotonic: equal movement of water
into and out of cell
Hypotonic solution: net water
movement into the cell
Hypertonic: net movement of water
out of the cell
Assessment
In your own words, explain why you feel
dehydrated after eating a large bag of
salty potato chips
Osmosis in the kitchen YouTube
Osmosis in plant cells
Plasmolysis in Elodea YouTube
Plasmolysis
hypertonic
environment: cell
loses water
Cell membrane
separates from cell
wall
Friday 1/4/13
AIM: How does the cell membrane
regulate osmosis?
DO NOW: Why do you feel dehydrated
after eating a large salty popcorn and
drinking a sugary soda?
HOMEWORK: Textbook read pages:
1- DEFINE active transport
2- List and describe the different types of
active transport
KScience - Animations
Osmosis in plants (Red
Onion) - YouTube
Add salt solution (hypertonic)
If I add fresh water to
Cell A and let it sit for
an hour what will
happen?
Complete the drawing
of picture B and
explain what has
happened.
Hypotonic environment
Water rushes into the cell and the cell
swells
Lysis: the cell bursts
– Cannot stop water from entering
What happens to single celled organisms
like the ameba?
Contractile vacuole
Monday 1/7/13
AIM: How does the cell use energy to
transport molecules across the plasma
membrane?
DO NOW: Use the picture displayed to
explain how the molecules will move:
How does the concentration
gradient determine the
direction of molecule
movement across the cell
membrane?
Active transport
Movement of substances against a
concentration gradient
From low to high
Needs energy
Membrane proteins use energy to move
individual molecules
How does active transport differ
from facilitated diffusion?
What happens to a plant cell when I place
it in salt water?
How is active transport different
from passive transport?
Passive transport does
not need energy to move
molecules from high to
low concentration
Active Transport uses
energy to move
molecules against the
concentration gradient
Differences between Active
transport and facilitated diffusion
Active Transport
– Uses energy
– Moves molecules from
low to high
concentration
– Moves molecules
against the
concentration gradient
Facilitated diffusion
– Does not use energy
– Moves molecules from
high to low
concentration
– Moves molecules
down the
concentration gradient
Why is active transport necessary
for homeostasis?
Certain molecules need to enter or leave
the cell against their concentration
gradient
Ion Transport
Cotransport
movement of 2
solutes together
often moves 1 solute
passively & other
actively
Assessment
In your notebooks draw the picture
depicted below and explain how molecules
move in the direction of the arrows