Download Cells & Their Environment

Chapter 4
Cells & Their
Environment
DO NOW
• 1) Grab a Chapter 4 packet
• 2) Try to answer questions 1 & 2 on
page one
• 3) Wait quietly to begin
Learning Targets
• 1) I can – predict the direction of
substance movement into and out of the
cells in terms of diffusion
• 2) I can – describe the importance and
role of ion channels and facilitated
diffusion in passive transport
Remember – Homeostasis?
• Passive
Transport
• Homeostasis
• Cells do this by controlling the
movement of substances across
their cell membrane
• Diffusion:
• Movement across the cell membrane
• Passive Transport = No cellular
energy required
• Try This: Write a sentence
using the word “diffuse”
•Diffusion:
•Movement of a substance from an area
of higher concentration to an area of
lower concentration
•Don’t have to use energy
Diffusion
Concentration
Gradient
• A difference in concentration of a
substance across a space – moving
from high to low concentration down
concentration gradient
• Equilibrium• When the substances are equally
divided among all areas then they
have reached equilibrium
• When concentration of a substance
is equal throughout a space
Diffusion Across the Cell
Membrane
• Diffusion
• *Remember – Does the cell
membrane just let anything
through? (what do we call this)
• Many molecules and ions enter or
exit the cell by diffusing across
the membrane
• They move DOWN concentration
gradient (high to low)
• Cell membrane is selectively
permeable
•
STAND UP!
Let’s try to model DIFFUSION
down a concentration gradient
and EQUILIBRIUM
Back to Learning Target
• ✔I can – predict the direction of
substance movement into and out of the
cells in terms of diffusion
• 1) Grab an index card.
• 2) Write a description of your
movement. Use the new terms you just
learned such as – diffusion, high to low
concentration, concentration gradient,
and equilibrium
• 3) Stand up and share with others
Crossing the Cell Membrane
• What
crosses the
cell
membrane?
• Usually only nonpolar or very small
molecules diffuse well through
nonpolar lipid bilayer
• But most polar molecules and ions
cannot pass through the lipid bilayer
• Thanks to transport proteins called –
channels – passageways are made
so polar molecules & ions can move
across the cell
Crossing the Cell Membrane
• Ion
Channels
• Each channel allows only a
specific substance to pass
through
• This is how the cell controls
what enters and leaves!
• Allows important ionic
substances to flow into cell
without contacting nonpolar
membrane parts
Crossing the Cell Membrane
• Ion
Channels
• Some channels remain open,
others are gated
• Ion channels include : Sodium
(Na), potassium (K), & Calcium
(Ca) that are important to cell
functions
• No energy needed (passive
transport)
Crossing the Cell Membrane
• Electrical
charge and
ion
transport
• 1. Ion charge can determine how it
moves across cell membrane
• 2. Inside of cell is usually negative
• 3. Positive ions tend to move into cell
more readily (opposites attract)
• 4. Negative ions move out of cell (like
charges repel)
• Ex: Na+, Cl-, K+, Ca2+
Crossing the Cell Membrane
• Facilitated
Diffusion
• 1. Carrier proteins are used to bind
to & carry amino acids and sugars
into the cell
• 2. Called “Facilitated” because the
carrier proteins “help” the amino
acids and sugars
• 3. Still no energy required, passive
• 4. Carrier proteins shield substances
from nonpolar interior of membrane
Back to Learning Target
• ✔I can – describe the importance and
role of ion channels and facilitated
diffusion in passive transport
• Numbers 1 & 2: Imagine you are a Na+
ion, describe how an ion channel works
for you
• Numbers 3 & 4: Imagine you are an
amino acid, describe how facilitated
diffusion works for you
Demonstration
• 1) Each group will need:
• Beaker with water
• Iodine solution
• A baggie with water and cornstarch
• Iodine is a “starch indicator” - when it
comes into contact with starch it turns
dark purple
• Starch is a large, complex sugar
• Iodine is a small, I- ion
DO NOW
• 1) Take out your Chapter 4 packet and
grab your textbook
• 2) Answer DO Now #1 questions on
page
• 3) Wait quietly to begin
Learning Targets
• 1) I can – describe the movement of
water in and out of the cell in terms of
osmosis
• 2) I can – differentiate between a
hypertonic, hypotonic, and isotonic
solution
Demonstration
• 1) Each group will need:
• A cup of distilled water
• A cup of salt water (place two spoonfuls of
salt in the other cup of water to make)
• Two small potato slices
• 2) Find a safe place in the room for your
cups, we will come back to them at the
end
Osmosis
• Osmosis
• Water molecules are small and
can diffuse through the cell
membrane
• 1. Diffusion of water through a
selectively permeable
membrane
• 2. Passive transport (no cellular
energy)
• 3. Water moves from high to
low concentration
Osmosis
• Osmosis
• 4. Water flows toward area with
high concentration of dissolved
particles
Osmosis – Three Types of
Solutions
• Osmosis –
Three
types of
Solutions
• The direction of water movement
depends on the concentration of
“free” water molecules inside
and outside the cell
• There are three solutions that
describe the movement of water
• Hypertonic
• Hypotonic (Think HIPPO)
• Isotonic
Osmosis – Three Types of
Solutions
• Osmosis –
Three
types of
Solutions
• Use page 77 in your textbook to
research each type
• When you finish, practice
explaining the difference
between each
• Hypertonic
• Hypotonic (Think HIPPO)
• Isotonic
Learning Targets
• ✔I can – describe the movement of water in
and out of the cell in terms of osmosis
• ✔I can – differentiate between a hypertonic,
hypotonic, and isotonic solution
• 1) Grab your cups from earlier and
observe your potatoes.
• 2) In your notes on p. describe the
solution your potato was in and the
movement of water
Solutions
• Hypertonic
Solution
• If the fluid outside the cell has:
• More dissolved particles than the
cytoplasm (higher concentration)
• Water diffuses:
• Out of the cell
• Effect on Cell
• Cell Shrinks
• Ex: Ever have a sore throat? – Salt
Water
Solutions
• Hypotonic
Solution
• If the fluid outside the cell has:
• Less dissolved particles than the
cytoplasm
• Water diffuses:
• Into the cell
• Effect on Cell
• Cell Swells
• Ex: Swollen doors on a humid day?
Solutions
• Isotonic
Solution
• If the fluid outside the cell has:
• The same dissolved particles as
the cytoplasm
• Water diffuses:
• Into and out of the cell at equal
rates
• Effect on Cell
• Cell stays the same size
Solutions
• Cell
bursting
can be
prevented
by:
• 1. Rigid cell walls in plants and
fungi
• 2. Contractile vacuoles in some
unicellular eukaryotes
• 3. Animal cell mechanisms
remove extra dissolved particles
in cell
DO NOW
• 1) Take out your Chapter 4 packet
• 2) Answer DO Now #2 questions on
page
• 3) Wait quietly to begin
Learning Targets
• 1) I can – describe the importance and
role of the sodium – potassium pump
and receptor proteins
• 2) I can – differentiate between
endocytosis and exoytosis
• 3) I can – compare active transport with
passive transport
Active Transport
• Active
Transport
• 1. Transport of substances
across membrane against
concentration gradients
• 2. Moves large sugars, amino
acids in or out of cell from low to
high concentration when
necessary for cell
Active Transport
• Active
Transport
• 3. Requires energy (ATP)
• 4. Carrier proteins bind to and
pump substances from one side
of the cell to the other from low
to high concentration
Active Transport
• SodiumPotassium
Pump
• 1. Keeps sodium, potassium
levels in and out of cell
balanced
• 2. Prevents sodium buildup in
cell because it continuously
diffuses in through ion channels
• 3. Excess sodium may cause
the cell to burst
• 4. Requires energy (ATP)
Active Transport
• Movement
in Vesicles
• Many proteins and
polysaccharides are too large to
be transported by carrier
proteins
• 1. Endocytosis- movement of
very large proteins and
polysaccharides into the cell
through vesicles
• Membrane forms a pouch around
substance that pinches off
Active Transport
• Movement
in Vesicles
• 2. Exocytosis- substance
moved by vesicle, to outside
cell, by binding to membrane
Active Transport
• Membrane
receptor
proteins
• Your body sends out “signal
molecules” to communicate to
all parts of the body ex:
hormones
• Receptor proteins in cell
membranes bind to specific
signal molecules, so cell can
respond to signal
• Allows distant cells to
communicate through release of
signal molecules
Active Transport
• Membrane
receptor
proteins
• When a signal molecule binds to
a receptor protein, its signal can
cause the cell to do 3 things:
• 1. Causes ion channels to open or
close their gates so ions do or do
not pass
• 2. Trigger second messengers
that carry out the signal’s
message within the cell
• 3. Activate enzymes to speed up
cellular reactions
Active Transport
• Membrane
receptor
proteins
• 4. Many drugs act by blocking
proper binding or signal
molecules to receptor proteins
• Bad: Heroin
• Good: Heart monitoring drugs
Back to Learning Targets
• ✔I can – describe
the importance and
role of the sodium –
potassium pump
and receptor
proteins
• ✔I can –
differentiate
between
endocytosis and
exoytosis
• Interview Questions:
• 1) What type of
active transport are
you?
• 2) How do you allow
movement to occur
in the cell?
• 3) Why is this good
for the cell? (What
does it
prevent/allow?)
Back to Learning Targets
• ✔) I can – compare active transport
with passive transport
• 1) Complete the t-chart comparing
active and passive transport
• 2) Compare your charts with other
students to see if you should
add/remove and information
Practice
• Create a pictionary of the main types of
passive transport and types of active
transport mechanisms. Define each,
state the method of movement, give
examples and make drawings to
illustrate each mechanism. Try to
complete this activity without your
notes- later you can go back and check
your work against your notes and the
textbook.
Real World Connection
• Drinking too much
water can be just as
bad as not drinking
enough water.
• Can cause
hyponatremia.
• This is because there’s
not enough sodium
(salt) in the cells.
• Drinking Gatorade can
help.