Cell membrane and Transport

1. The Cell Membrane
Aka: Phospholipid bilayer
http://study.com/academy/lesson/polar-molecule-definition-examples.html

2. Warm Up!
Part A
Using the image provided answer the followings questions:
1. How many layers make up the cell membrane?
2. What is a phospholipid made up of?
3. Would the tails of a phospholipid attract or repel water?
4. What fluid is found on the interior and exterior of the
cell?
Part B
Think of 1 question you have about the cell membrane
based on the image.

3. Structure of cell membrane

4. The Cell (Plasma) Membrane
• Separates the interior of a cell from it’s surroundings
• Controls the traffic of chemicals in and out of the cell
• How the membrane works is due to its structure
• The plasma membrane is made of proteins and lipids
• The lipids are called phospholipids

5. Phospholipids
• The head is made of phosphate
• Head: HydroPHILIC, POLAR
• LOVE WATER
• Tails are made of 2 fatty acid molecules
• Tails: HydroPHOBIC, NON-POLAR
• HATE WATER
https://www.youtube.com/watch?v=moPJ
kCbKjBs

6. Think Time!
If you were to drop 10 phospholipids into the
water, what would happen? Draw your
prediction.
X 10
https://www.youtube.com/watch?v=QQgXfuFyKM4

7. Cell (Plasma) membrane
• Also called a phospholipid bilayer
• Phosphate heads face the watery
inside and outside of the cell
• Fatty acid tails are shielded from
the water
• Form barrier
• POLAR molecules GET IN
– Exp. Carbon Dioxide and
Oxygen
• NON POLAR molecules and LARGE
molecules DO NOT GET IT
– Exp. Ions: Na+ (charged atoms),
and sugar

8. Membranes regulate the traffic of molecules
• Lots of molecules move across
the PM
• Two-way traffic, moving in and
out of cell
• One way molecules move across
the PM is by diffusion
• Diffusion is the net movement
of the particles of a substance
from where they are more
concentrated to where they are
less concentrated
• Examples: perfumes, cordial in a
glass of water
• Diffusion

9. Model Diffusion
• High to Low concentration
• You will have 3 minutes to discuss within
the class how to model diffusion and
prepare to show it to the teacher.
• Work together and communicate!

10. Type of
Transport
Transport
Protein
Used?
Direction of
movement
Requires Energy
input from cell?
Classification of
transport?
Types of
Substances
Simple
Diffusion
Facilitated
Diffusion
Active
Transport
Complete the chart for your notes:

11. Transport Through the Membrane –
Passive method
• Simple
Diffusion
• Facilitated
Diffusion
• Active
Transport

12. Simple Diffusion
• No transport protein used
• Movement WITH the
concentration gradient
(high to low)
• No additional cell energy
required
• PASSIVE
• Examples: water, carbon
dioxide and oxygen

13. Concentration Gradient - when there is a
difference in concentrations
• High concentration: more particles
• Low concentration: fewer particles
• In diffusion, particles move from high to low concentration to
reach an equal concentration (equilibrium) on each side.

15. Passive Transport
• Sugars can not cross the PM easily
• They are helped across by transport proteins
• This is called facilitated diffusion
• In this way ions and small polar molecules can
cross
• Facilitated diffusion
http://click4biology.info/c4b/2/cell2.4.htm#diff

16. Type of
Transport
Transport
Protein
Used?
Direction of
movemen
t
Requires
Energy
input from
cell?
Classification
of
transport?
Types of
Substanc
es
Simple
Diffusion
NO With
concent.
gradient
NO PASSIVE WATER,
CO2, O2
Facilitated
Diffusion
Yes:
Channel
Proteins or
Carrier
Proteins
With
concent.
gradient
NO PASSIVE GLUCOSE
Active
Transport

17. Carrier Proteins

18. Channel Proteins

19. Osmosis
• Osmosis is the passive transport of water across a
selectively permeable membrane from an area of high
conc to low conc
• Imagine a sealed bag containing a sugar solution in a
beaker of pure water
• Water can pass through the bag (membrane)
• Sugar molecules can’t
• Solution with higher concentration of solutes – hypertonic
• Solution with a higher concentration of water – hypotonic
• What will happen?
• Isotonic?
• Osmosis
http://www.youtube.com/watch?v=DpVbcJY4am
A

20. Comparing Passive & Active Transport

21. Type of
Transport
Transport
Protein
Used?
Direction of
movement
Requires
Energy
input from
cell?
Classification
of
transport?
Type of
Substan
ce
Simple
Diffusion
NO With
concent.
gradient
NO PASSIVE WATER,
CO2, O2
Facilitated
Diffusion
Yes:
Channel
Proteins
or Carrier
Proteins
With
concent.
gradient
NO PASSIVE GLUCOSE
Active
Transport
Yes:
Carrier
Proteins
Against
concent.
gradient
YES ACTIVE Na+ and
K+ ions

22. Active Transport
• When a cell uses energy to move molecules
or ions across a membrane, it is called Active
Transport
• Transport pumps are needed. These are
made from….
• Protein
• From area of low concentration to an area of
high concentration
• Need energy in the form of ATP
• Na+ is pumped out of the cell and K+ is
pumped in by this process
• Large molecules use vesicles – small

23. Active Transport

24. Other Types of Active Transport
• Endocytosis – the process of taking
material into the cell by folding in pockets of
the cell membrane into pouches called
vesicles
– Phagocytosis – endocytosis involving large
solid particles
– Pinocytosis – endocytosis involving liquid
• Exocytosis – the process of removing
material out of the cell where vesicles merge
with the cell membrane to release contents

25. 25
EX: Sodium-Potassium Pump
3 Na+ pumped in for every 2 K+ pumped out

26. • Exocytosis - moving
materials out
• Endocytosis: Moving
materials in
26
Too large  Must be packaged in membrane sacs
called vesicles
• It requires energy
Moving the “Big Stuff”

27. Endocytosis is the case when a molecule causes
the cell membrane to bulge inward, forming a
vesicle.
Phagocytosis is the type of endocytosis where
an entire cell is engulfed.
Pinocytosis is when the external fluid is
engulfed.
27

28. 28

29. Endocytosis and Exocytosis