Download cell membrane and passive transport

Bell Work:
Draw a phospholipid bilayer (double
layer of phospholipids) and arrange the
tails on the inside
Membrane Structure and
Cell Transport
Chapter 5
Objectives:
CLE 3210.1.5 - Compare different models to
explain the movement of materials into and
out of the cell.
SPI 3210.1.8 - Compare active and passive
transport.
RLE 2010.2.1 - Recognize the importance of
homeostasis as a survival mechanism.
Choose with your shoulder partner:
Homeostasis
•
Define homeostasis:
A tendency toward a state of equilibrium
•
Macro example:
•
Micro example:
We maintain a stable body temperature.
Cells use the cell membrane to regulate what comes in
and out of the cell to keep steady levels of nutrients,
water and other substances.
Cell Membrane - Function
1.All cells have a cell membrane
2.Functions:
a.Controls what enters and
exits the cell to maintain
an internal balance called
homeostasis
b.Provides protection and
support for the cell
Cell Membrane - Structure
3.Structure of cell membrane
Lipid Bilayer -2 layers of
phospholipids
a.Phosphate head is polar
(water loving)
b.Fatty acid tails non-polar
(water fearing)
c.Proteins embedded in
membrane
Semi – Permeable
(Selectively Permeable)
•allows certain
molecules or
substances to pass
through it
•Keeps other
molecules out
•The structure helps it
be selective!
Frogs
Explain to
your lizard
what semipermeable
means
Demonstration
• Cornstarch
• Plastic bag (represents a cell with a
semi-permeable membrane)
• Beaker w/ water and Lugols Iodine
Prediction:
• Will Iodine be allowed to pass through
the membrane?
• How will we know?
Controlled via the Cell Membrane
Passive Transport
Active Transport
Does NOT require energy, moves from HIGH
concentrations to LOW concentrations
Diffusion
Moves small molecules,
like CO2 & O2 gases,
directly through the
membrane
Hypertonic
Water moves out of the
cell & it shrinks
Osmosis
Movement of water
across the membrane
3 Types of
Solutions
Isotonic
Water moves
equally in and
out of the cell;
it stays the
same size
Facilitated
Diffusion
Uses transport proteins
to move large molecules
through the membrane
WITHOUT energy
Hypotonic
Water moves into the
cell & it swells
DOES require energy, moves from LOW
concentrations to HIGH concentrations,
moves LARGE molecules (glucose) via
transport proteins
Protein
Pumps
Transport proteins that
require energy to do
work. Example: Sodium
/ Potassium Pumps are
important in nerve
responses.
Endocytosis
Materials ENTER the cell
through a vesicle
formed by the
membrane
Exocytosis
Materials EXIT the cell
through a vesicle
formed by the Golgi
Body
Cell Membrane Transport
•
Two main types of cell transport:
o
Passive:
the movement of
substances across
the cell membrane
without energy.
o
Weeee!!
!
high
low
Active:
the movement
of substances
across the cell
membrane with
the use of
energy.
This will
be hard
work!!
high
low
Lizards:
Explain to your
frogs the
difference
between passive
and active
transport
Types of Passive Transport
(No energy) (High to Low)
•
Diffusion
Movement of SOLUTES from high concentration to low
concentration.
•
•
Osmosis
Movement of WATER molecules from an area of high
water concentration to an area of lower water
concentration.
Facilitated Diffusion
Diffusion of molecules across a membrane using protein
channels or pores
Concentration
Concentration:
The amount of a substance in a given volume
Two parts needed to determine concentration:
Solvent:
•
•
• The substance with the greatest volume
• What the solute is dissolved in.
Solute:
• The substance with the smaller volume
• The substance(s) that are dissolved in the solvent.
Solute vs Solvent
Example: Salt water
Solvent? Water
Solute? Salt
•
•
Solute and Solvent
Example: Food coloring in water
Concentration Gradient
Passive Transport = High to Low
Why will things move from high concentration
to low concentration?
All molecules
are moving.
As they bump
into each other
they move faster
until there is
even space
between them.
Passive Transport Leads to
Equilibrium
Equilibrium:
When the
concentration of
molecules is the
same throughout
the space the
molecules
occupy.
Frogs:
Explain why
molecules
want to move
from areas of
high
concentration
to low
How does this affect cells?
Diffusion:
Lungs: can send CO2 out of the red blood cells and get O2 in
Cells: can get O2 into them and send out CO2
Osmosis:
When cells need more water to perform hydrolysis, can pull
water in from the blood.
If cells need to remove water that built up after many sets of c
tondensation, they can send water out to blood
• Remember:
All passive transport moves
from high to low concentration trying to create
an equilibrium
Facilitated Diffusion (Passive)
Definition:
• Diffusion with the help of carrier protein channels
• Usually for large molecules – like Glucose
Video - "Facilitated Diffusion”
Facilitated Diffusion (Passive)
•Some
molecules are
too big to
enter the cell
without help
Demonstration Check:
Record the results of the corn
starch in iodine experiment.
Passive Transport Review:
Three types:
small solutes (O2 or CO2) moving across the
Diffusion: membrane
Osmosis: movement of water across the membrane
Facilitated diffusion: larger solutes (glucose)
•
•
•
moving across the membrane
through channels or pores
Common Characteristics:
Don't use any energy
Move from high to low concentration
•
•
Lizards:
Summarize the
3 types of
passive
transport to
your frog
Exit Ticket
•Differentiate between diffusion and
facilitated diffusion?