Download Section 7.3 Cell Transport

Activating Prior Knowledge
Define the term homeostasis.
2. Give the function of each of the following organelles:
1.
 Cell membrane –
 Lysosome –
 Golgi Apparatus –
3. How does the cell membrane maintain homeostasis?
4. Label and describe as many parts/features of the cell
membrane as you can.
5. Distinguish between peripheral and integral proteins.
Put in diagram above.
1) Define HOMEOSTASIS
 Maintaining a relatively constant or stable internal
environment, even when external conditions change
dramatically
2) Give the function of each of the
following organelles
 Cell (plasma) membrane
 a flexible boundary between a cell and its environment
 allows nutrients into the cell no matter what the external
conditions are.
2) Give the function of each of the
following organelles
 Lysosome
 Clean up crew – break down organelles that have
outlived their usefulness
 Break down lipids, carbs, proteins
 Golgi Apparatus
 Modifies, sorts and packages proteins and other
materials from the ER for storage in cell or release
outside of cell
3) How does the cell membrane
maintain homeostasis?
 Cell membranes help organisms maintain
homeostasis by controlling what substances may
enter or leave cells
4) Label and describe as many parts/features of the cell
membrane as you can:
Components of Cell Membrane:
Plasma Membrane (5:15)
Key Terms Associated with
Transport:
 Concentration Gradient - difference in
amount of molecules across space
 Down the concentration gradient:

Higher Concentration  Lower Concentration
 Up the concentration gradient:

Lower Concentration Higher Concentration
 Equilibrium - when the concentration is the
same throughout
Concentration Gradient:
Types of Transport:
 Passive Transport– movement of
molecules down their concentration
gradient without the use of energy
 Active Transport- movement of
molecules up their concentration
gradient with the use of energy
Biology Cell Transport 2:02
Passive and Active Transport
Structure Of The Cell Membrane - Active and Passive Transport (6:52)
Passive Transport:
 Determining Factors
 Size
 Type of Molecule
 Chemical Nature of
membrane
 Small, nonpolar,
hydrophobic molecules
 4 Types of Passive
Transport
 Diffusion
 Osmosis
 Facilitated Diffusion
 (Diffusion) Ion channels
Diffusion:
Diffusion:
 Process by which molecules tend to move from an area
where they are more concentrated to an area where
they are less concentrated (passive)
Osmosis:
 Diffusion of water through a selectively permeable
membrane (passive)
 from an area of higher water concentration to an area
of lower water concentration
Osmosis:
How Osmosis Works (1:40)
Solutions Can Be:
 ISOTONIC - solute concentration SAME on each
side of membrane
 Water diffuses in and out of the cell at the same rate
 Effect: No net change in cell size
Water Out
Cell size stays
the same
Water In
Solutions Can Be:
 HYPOTONIC - Solution with a solute
concentration lower than cell
 Water will diffuse INTO cell until equilibrium
 Effect: The cell swells and may burst
Cell size gets
LARGER
Water In
Solutions Can Be:
 Hypertonic - Solution with a solute
concentration higher than the cell
 Water will diffuse OUT cell until equilibrium
 Effect: The cell shrinks
Water Out
Cell Size gets
SMALLER
Effects of Osmosis:
 Water diffuses from a hypotonic to a
hypertonic solution
Egg Demo:
 Water
 Hypotonic solution
 Corn Syrup
 Hypertonic solution
The Sci Guys: Science at Home - SE1 - EP14: The Naked Egg and Osmosis
Dealing with Osmosis:
 Plants (root cells) swell in a hypotonic environment
 The swelling stops when the cell membrane is pressed against the
cell wall

The cell wall is strong enough to resist the pressure, called turgor
pressure

(pressure exerted against the cell wall in a hypotonic environment)
Cytolysis and Plasmolysis
 Cytolysis – In a hypotonic solution, cells can swell
and eventually burst
 Plasmolysis - In a hypertonic environment, water
leaves the cell and the cell shrinks away from the cell
wall as turgor pressure is lost
Contractile Vacuole
 Unicellular freshwater organisms (Paramecium) live in a
hypotonic environment
 Contractile Vacuole - collects excess water and pumps it
out of cell
Review Questions:
1.
Toward what condition does diffusion eventually lead, in the
absence of other influences?
2. How is osmosis related to diffusion?
3.
If the concentration of solute molecules outside a cell is lower than
the concentration in the cytoplasm, is the external solution
hypotonic, hypertonic, or isotonic to the cytosol?
4. Sea water has a higher concentration of solutes than do human
body cells. Why might drinking large amounts of sea water be
dangerous to humans?
Facilitated Diffusion
 Movement of specific molecules across cell
membranes through protein channels
 Passive transport
 diffusion of materials across a cell membrane assisted
by carrier proteins
Facilitated Diffusion (1:18)
Facilitated Diffusion
 Move molecules, (that cannot diffuse easily), down
their concentration gradient
 Move into or out of cell
 Examples: Glucose, Amino Acids, Ions,
Polar molecules (water)
 Assisted by carrier proteins on the membrane
 Specific to one type molecule
 More protein=faster diffusion
Protein Channels and
Carrier Proteins
carrier proteins allow molecules to
pass through when their shape
changes
molecules pass through
channel proteins that span
the membrane
the carrier protein changes shape
and releases the molecule to the
side of the membrane that has the
lower concentration
Gated Channels are able to
regulate the passage of particles
by opening and closing gates
that prevent passage
Some gated channels open in response to the difference in ion concentration
across the membrane. Other gated channels open when a specific substance
binds to the channel protein.
Facilitated Diffusion of Glucose
through a carrier protein:
Ion Channels—Na , K , Ca
+
 Provide protein channels
for ions to diffuse
 Specific to Ion
 Two types
1.
2.
Open
Gated—open and
close in response to
specific stimuli
+
2+,
Cl-
Passive and Active Transport
Structure Of The Cell Membrane - Active and Passive Transport (6:52)
Membrane Transport in Cells
Symport, Antiport, Cotransport 5:59
Active Transport:
 Cells use energy to move up concentration gradient
 ATP supplies energy
 Carrier proteins act as pump
Active and Passive Transport (6:12)
SODIUM-POTASSIUM PUMP:
 In animal cells transport Na+ and K+ up
the Concentration Gradient
 3 Na+ moved outside of cell
 2 K+ moved inside cell
 Builds up a chemical and electrical
gradients for each ion.
 These gradients can be used to drive other
transport processes.
 In nerve cells these gradients are used to
propagate electrical signals that travel
along nerves.
 Therefore the action of nervous tissue
requires ATP to generate resting potentials.
Membrane Transport : Animation 3:18
ATP – Adenosine Triphosphate
• Cells release energy from ATP molecules by subtracting a
phosphate group
• The energy of ATP is locked in the bonds between the
phosphate groups.
• When the terminal phosphate group of the ATP molecule
is removed by hydrolysis, energy is released and adenosine
diphosphate (ADP) and phosphate are formed.
Steps for Transport
1.
3 Na+ bind to carrier
protein in cytoplasm
 Carrier protein splits
phosphate group from ATP
2. P group binds with
carrier protein—shape
changes—releases Na+
3. Now protein can pick
up 2 K+ on outside
4. Carrier protein changes
shape releases K+
Sodium Potassium Exchange Pump
Exocytosis and Endocytosis:
 Transport large molecules across membrane
 Transport a large amount of small molecules
 Energy (ATP) used
Endocytosis and Exocytosis
Exocytosis
 Exporting large molecules
outside of cell
 Process
 Packaged in Golgi Apparatus
 Vesicle transports to cell
membrane
 Vesicle fuses to membrane


Contents released
Vesicle becomes part of
membrane
Endocytosis and Exocytosis
Endocytosis
 Cells take in (ingest) substances
 Process
 Depression in cell membrane folds in enclosing material
from outside of the cell
 Pinched off forming a
membrane-bound vesicle


Vesicle fuses with lysosomes
Fuse with other organelles
3 Types of Endocytosis:
 Pinocytosis—”Cell Drinking”
 Ingestion of tiny droplets
 Phagocytosis-”Cell Eating”
 Engulfs large, solid molecule or whole cells
(like bacteria)
 Receptor-mediated—Specific
 Ingestion of specific substances that bind to receptor
proteins on specialized areas of cell membrane
3 Types of Endocytosis:
Review Questions:
1.
Explain the difference between passive and active transport.
2. What provides the energy that drives the sodium-potassium
pump?
3.
Explain the difference between phagocytosis and pinocytosis.
4. During intense exercise, potassium tends to accumulate in the
fluid surrounding muscle cells. What membrane protein helps
muscle cells counteract this tendency? Explain your answer.