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TOPIC 8
Cell Membrane & Transport
@ NSBHS
KEY TERMS
1. Phospholipid
2. Fluid Mosaic
Model
3. Selective
Permeability
4. Passive Transport
5. Diffusion
6. Facilitated
Diffusion
7. Osmosis
8. Active Transport
9. Endocytosis
10. Exocytosis
LEARNING TARGETS… I will be able to…
1. Explain how both passive and active
transport move materials across the
cell membrane
2. Predict the impact to a plant or
animal cell if placed in various types
of solutions:
a. Hypotonic
b. Hypertonic
c. Isotonic
3. Explain why cells are limited in size
in terms of nutrient and waste
transport
4. Create a model to simulate how a
cell membrane works
New Smyrna Beach High School
2014-15
TEXTBOOK
Chapter 3, Cell Structure & Function
Why is studying the cell membrane so important?
Cell Membrane Diseases
Cell membrane diseases are life-threatening disorders that are genetic in nature, and they usually work against proteins in our body that
are key to ion channels and various receptors within the membrane. These diseases work by either disrupting the normal functions of the cells
or by simply affecting the cell membrane. Many of these disorders contain other components as well.




Hyaline Membrane Disease: Commonly associated with preterm infants, Hyaline membrane disease affects the lungs at the time of birth
causing respiratory distress. As a result, the lungs require abnormal levels of oxygen & carbon dioxide exchange after birth.
Alzheimer's Disease: The oxidative stress caused by Alzheimer's disease in the brain results in phospholipid altercations. Phospholipids are a
key component of our cell membranes. These altercations compromise the cell membrane, therefore disrupting the function of the brain
cells.
Cystic Fibrosis: is a disease that brings about an excessive production of fluid in the lungs due to a defective calcium-ion channel. This
channel contains a protein that is important to the cell membrane of our lungs. The channel controls the level of fluids and mucus in our
lungs. When this channel mutates into cystic fibrosis, it causes the mucus to build up in the lungs, thus making it hard to breath.
Duchenne Muscular Dystrophy: This disease affects dystrophin in the muscle cell. Dystrophin allows the muscle cell wall to connect with the
intracellular section. In the absence of dystrophin, the CM would be incapable of repairing itself, destroying it & bringing about MD.
How Muscle Cells Seal Their Membranes
ScienceDaily (Mar. 14, 2012) — Every cell is enclosed by a thin double layer of lipids that separates the distinct internal environment of
the cell from the extracellular space. Damage to this lipid bilayer, also referred to as plasma membrane, disturbs the cellular functions and may
lead to the death of the cell. For example, exercise like downhill walking tears many little holes into the plasma membranes of the muscle cells in
our legs. To prevent irreparable damage, muscle cells have efficient systems to these holes again. With a laser, the researchers burned tiny holes
into the plasma membrane of muscle cells and followed the repair of the holes under the microscope. They showed that membrane vesicles
together with two proteins Dysferlin and Annexin A6 rapidly form a repair patch. Researchers at Karlsruhe Institute of Technology (KIT) and
Heidelberg University have succeeded for the first time in observing membrane repair in real-time in a living organism. Researchers suggest that
the cell assembles a multilayered repair patch from the inside that seals off the cell's interior from the extracellular environment. It was also
found that there is a specialized membrane area that supplies rapidly the membrane that is needed for sealing the plasma membrane hole. The
results may contribute to the development of therapies for human myopathies (muscular diseases) and open up new possibilities in
biotechnology.
Chemists Synthesize Artificial Cell Membrane
ScienceDaily (Jan. 26, 2012) — Chemists have taken an important step in making artificial life forms from scratch. Using a novel
chemical reaction, they have created self-assembling cell membranes, the structural envelopes that contain and support the reactions required
for life. "One of our long term, very ambitious goals is to try to make an artificial cell, a synthetic living unit from the bottom up -- to make a living
organism from non-living molecules that have never been through or touched a living organism," Devaraj, an assistant professor at UCSB said.
"Presumably this occurred at some point in the past. Otherwise life wouldn't exist." By assembling an essential component of earthly life with
no biological precursors, they hope to illuminate life's origins. Nature uses complex enzymes that are themselves embedded in membranes to
accomplish this, making it hard to understand how the very first membranes came to be. They created the synthetic membranes from a watery
emulsion of an oil and a detergent. Alone it's stable. Add copper ions and sturdy vesicles and tubules begin to bud off the oil droplets. After 24
hours, the oil droplets are gone, "consumed" by the self-assembling membranes.
Mechanism of Sculpting the Plasma Membrane of Intestinal Cells Identified
ScienceDaily (Aug. 2, 2011) — The research group of Professor Pekka Lappalainen at the Institute of Biotechnology, University of
Helsinki, has identified a previously unknown mechanism which modifies the structure of plasma membranes in intestinal epithelial cells.
Typically, modifier proteins serving the cell typically twist the cell membrane into pipe-like, concave or convex structures. The parts protruding
and drawn in like this are vital for cell movement, shape transformation and nutrient intake. Unlike other proteins with a similar function, the
new protein -- named 'Pinkbar' -- creates planar (flat) membrane sheets. Further research investigates the potential connection of this protein
with various intestinal disorders. A dynamic plasma membrane surrounds all eukaryotic cells. Membrane plasticity is essential for a number of
cellular processes; changes in the structure of the plasma membrane enable cell migration, cell division, intake of nutrients and many
neurobiological and immunological events. Earlier research has shown that certain membrane-binding proteins can 'sculpt' the membrane to
generate tubular structures with positive or negative curvature, and consequently induce the formation of protrusions or invaginations on the
surface of the cell. These membrane-sculpting proteins are involved in various vital cellular processes and can control the shape of the plasma
membrane with surprising precision. Many of the membrane proteins have also been linked to severe diseases such as cancer and neurological
2
syndromes. In humans, Pinkbar is only found in intestinal epithelial cells where it may be involved in the regulation of intestinal permeability. In
the future, it will be important to identify the exact physiological function of Pinkbar in intestinal epithelial cells and to study the possible links of
this protein to various intestinal disorders
Concept Map
Types of Cell Transport
Directions: Given the following terms, complete the Concept map showing how these words are
related. Use the definitions on the screen for help:
Active transport, Endocytosis, Diffusion, Facilitated diffusion, Passive Transport, Osmosis,
Exocytosis, Pinocytosis, Phagocytosis, Transport through Cells
1.
2.
3.
4.
6.
5.
7.
8.
9.
10.
3
Transport Into and Out of the Cell
DIFFUSION, OSMOSIS & THE CELL MEMBRANE
Underline/Highlight the answers to the questions within the article
1. What is the
relationship
between transport
& the Cell
Membrane?
 All living things have certain requirements they must satisfy in order to remain alive.
These include exchanging gases (usually CO2 & O2), taking in water, minerals, &
food, & eliminating wastes. These tasks occur at the cellular level, & require that
molecules move through the plasma/cell membrane that surrounds the cell.
 This membrane is a complex structure that is responsible for separating the contents
of the cell from its surroundings, for controlling the transport of materials into & out
of the cell, & for interacting with the environment surrounding the cell.
2. What is Selective
Permeability &
how does it relate
to homeostasis?
 The membrane selects or chooses the materials it wants to pass into or out of the
cell. This is referred to selective permeability or the membrane being selectively
permeable. The membrane will ‘choose’ to let the ‘good stuff’ in and keep the ‘bad
stuff’ out or vice versa. Because it does so, it maintains stability or homeostasis in
the cell.
2 METHODS OF MOLECULE MOVEMENT in & out of the cell
Passive and Active Transport
3. How is PASSIVE
TRANSPORT like
“taking the easy
road”?
1. PASSIVE TRANSPORT does NOT require energy expenditure, spontaneous!
________________________________________________________________________
ACTIVE TRANSPORT requires that the cell use energy that it has obtained from food to move the molecules (or larger particles) through the cell membrane.
 Passive transport does not require energy & work. There are several different types
of this easy movement of molecules—the two major ones are Diffusion & Osmosis.
4. What is
DIFFUSION?
 The principle type of passive transport is diffusion. DIFFUSION is the movement of
molecules from an area in which they are highly concentrated to a area in which
they are less concentrated; like spraying perfume in an enclosed room. When the
molecules are even throughout a space - it is called equilibrium.
5. Draw the next 4
boxes showing
how the molecules
will move
throughout the
space until it finally
reaches
equilibrium.
6. Why do you think
that equilibrium
inside the cells is
important?
_____________________________________________________________________
_____________________________________________________________________
4
Passive Transport, Continued...
7. What is
OSMOSIS?


A second type of Passive Transport is Osmosis.
OSMOSIS is the diffusion of water—and water ONLY—(across a membrane)
from a higher concentration to a lower concentration.
·
Osmosis is a water specific process!!
 For a cell to survive, concentrations of many substances need to be the same on both
sides of the cell membrane. If the cell does not pump out all of its extra ions, for
example, to even out the concentrations, the water is going to move in. This can be very
bad. The cell can swell up and explode. The classic example of this type of swelling
happens when red blood cells are placed in water. The water rushes in to the cells, they
expand and eventually rupture!
 In the picture to the right, osmosis is
taking place: the water molecules
are moving across a selectively
permeable membrane.
Water molecules are the small shapes, and
the solute (solid particle) is the bigger circles.
Solute = _______________________________________
Solvent = ______________________________________
8. In the diagram at
the right, color
the water
molecules blue
and the sugar
molecules pink.
9. Since Osmosis is
water moving
from HIGH to
LOW amounts,
indicate with an
arrow which
direction the
water is moving
in the picture.
5
Passive Transport ,Continued...
THREE TYPES OF SOLUTIONS

"ISO" means the same —> An isotonic solution is one in which the amount
(concentration) of solute (salt) is equal on both sides, the water in the solution will move
back in forth but it won't have any result on the overall amount of water on either side.
EX: HypOtonic

HYPO" means less, in this case there are less solute (salt) molecules outside the
cell, since salt sucks, water will move into a cell
11. What happens
to plant cells
when water fills
the vacuole?
What happens
to animal cells
when water fills
the cell?

When water from the solution moves into the cell. The cell will gain water and
grow larger.
In plant cells, the central vacuoles will fill and the plant becomes stiff and rigid, the
cell wall keeps the plant from bursting. This pressure is called _________________
In animal cells, the cell may be in danger of bursting; organelles called contractile
vacuoles will pump water out of the cell to prevent this.
EX: ISOtonic
10. In an ISOtonic
solution,
indicate with
an arrow,
which way the
water moving?


12. In a hypotonic
solution,
indicate with
an arrow
which way the
water is
moving?
EX: Hypertonic
13. What happens
to plant cells
when water is
lost? What
about animal
cells?
14. In a hypertonic
solution,
indicate with
an arrow
which way the
water moving?

The word “HYPer” means more. In this case. There are more solute (salt)
molecules outside the cell, which causes the water to be sucked out of the cell



In plant cells, the central vacuole would lose water and shrink, causing wilting.
In animal cells, the cells shrink.
In both cases, the cell may die…. That is why it is dangerous to drink sea water – it
is a myth that drinking sea water will case you to go insane, but people marooned at
sea will speed up hydration (& death) by drinking sea water – SALTS SUCKS! —
That is also why “salting fields” was a common tactic during war, it would kill the
crops in the field, thus causing food shortages.
6
Active Transport
15. How is ACTIVE
TRANSPORT
like “Taking the
Hard Road”?
16. EX. of Active
Transport = The
Sodium
Potassium Pump

Active transport requires that the cell
use energy, because substances are
moving against the concentration gradient.

It is the opposite from passive transport
in that the amount of material moves from
a low amount to a high amount – like going
UPHILL, instead of downhill. The liquids
inside and outside of cells have different
substances. Sometimes a cell has to work
and use some energy to maintain a proper
balance of molecules.

Process that maintains balance of sodium inside cell and potassium outside of
cell; both substances are moving against the gradient (uphill) which requires ATP
(energy)

Active transport usually happens across the cell membrane. There are thousands
of proteins embedded in the cell's lipid bilayer. Those transport proteins do
much of the work in active transport. They are positioned to cross the membrane
so one part is on the inside of the cell and one part is on the outside. The
membrane proteins are very specific. One protein that moves glucose will not
move calcium (Ca) ions. There are hundreds of these membrane proteins in the
many cells of your body.

Many times, proteins have to work against a concentration gradient. That term means
they are pumping something (usually ions) from areas of lower to higher concentration….
Like going UPHILL. This happens a lot in neurons (nerve cells). The membrane proteins
are constantly pumping ions in and out to get the membrane of the neuron ready to
transmit electrical impulses.
17. Highlight the
arrows – why are
particles moving
back and
forth???
18. EX. of Active
Transport =
Proteins in the
Membrane
Protein channels
19. Color the Protein
Channels purple.
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Active Transport, continued...
20. EX: ENDOcytosis

Process by which the cell takes in / out? large particles by engulfing them
21. EX: EXOcytosis

Process by which the cell gets rid of particles; opposite of _______cytosis.

Even though proteins are working to keep the cell alive,
their activity can be stopped. There are poisons that
stop the membrane proteins from transporting their
molecules. Those poisons are called inhibitors.
Sometimes the proteins are destroyed and other times
they are just plugged up.
Imagine that you are a cell and have ten proteins
working to pump calcium into the cell. What if a poison
came along and blocked eight of them? You could not
survive with just two pumps working and would slowly
die. It would be like expecting you to breathe with your
mouth and nose plugged up!


Dynamic equilibrium occurs when 2 opposing actions occur at the same rate.
22. Label the part of
the diagram
showing
Endocytosis AND
Exocytosis
23. LOOK at the
diagram: What
kind of particles
would you want
your body to get
rid of? What kind
of particles would
your body WANT
to engulf?
24. Why is it important
to know what
Inhibitors do
25. Why is it better for
cells to be in
equilibrium?

If you were to poke a hole in the bottom of the bucket,
water would leak out. This system would not be at
equilibrium because there is action taking place water is leaking out - and the water level in the bucket
would drop.
However, if you were to begin pouring
water into the bucket at the same rate that it was
leaking out, the water level in the bucket would stay
the same because the rate at which the water is
entering the bucket is equal to the rate at which it is
leaking out. This is an example of dynamic
equilibrium. It means the cell is healthy!
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