This document summarizes different types of cell transport mechanisms. It describes passive transport mechanisms like diffusion, facilitated diffusion, and osmosis which move particles down concentration gradients without energy. Active transport mechanisms like the sodium-potassium pump use energy to move particles against concentration gradients. Endocytosis and exocytosis are described as mechanisms to move larger particles in and out of cells. The cell membrane, made of a phospholipid bilayer, regulates these transport processes to maintain homeostasis.

1. Section 8.3
Cell Transport

2. Diffusion & Osmosis
Diffusion
Movement of particles from an
area of high concentration to low
concentration
Osmosis
Diffusion of water across a
selectively permeable membrane

3. Selectively Permeable Membrane
Only certain
molecules can
pass and at
certain times

4. Solutions
Hypotonic Solution
Concentration of dissolved
substances is lower on the
outside of the cell
Isotonic Solution
Concentration of dissolved
substances is the same as the
outside of the cell
Hypertonic Solution
Concentration of dissolved
substances is higher on the
outside of the cell

5. Animal Cells in Solutions
Hypotonic Solution
Osmosis causes too much
water to move into the cell
Isotonic Solution
Osmosis does not occur.
Cell stays the same
Hypertonic Solution
Osmosis causes water to
move out of the cell
Lysed Normal Shriveled

6. Plant Cells in Solutions
Hypotonic Solution
Osmosis causes too much
water to move into the cell
Isotonic Solution
Osmosis does not occur.
Cell stays the same
Hypertonic Solution
Osmosis causes water to
move out of the cell
Turgid Normal Plasmolysed

7. Section 4.1
Membrane Structure

8. Plasma Membrane

9. Plasma Membrane
• Is selectively
permeable
• Maintains
homeostasis
• Consists of
phospholipid bilayer
structure

10. What on earth is a phospholipid bilayer?!?
• Contains phosphate groups (heads) and fatty acid
chains (tails)
• The phosphates are hydrophilic –meaning, they love
water
• The fatty acid chains are hydrophobic –meaning, they
hate water

11. Hydrophilic
phosphate head
Hydrophobic
fatty acid tails
I LOVE water!
We don’t!!

12. Phospholipid Bilayer
•Phospholipid
sandwich!
•Phosphate heads
are the bread
•Fatty acid tails are
the meat
Water passes easily past hydrophilic heads, however, they can’t move
through the hydrophobic tails

13. Fluid Mosaic Model
”Fluid” because it is flexible
“Mosaic” because of all the
small embedded
proteins/molecules that
make one big picture

14. Embedded Proteins & Molecules
• Cholesterol: Adds structure to the membrane
• Transport proteins: Create a passageway in the membrane

15. The Cell Membrane & Homeostasis
• The cell membrane is responsible for
maintaining homeostasis within the cell
• Homeostasis is a stable, internal environment
• The cell membrane maintains homeostasis
through balancing the pH, temperature,
glucose (sugar intake), water balance
• It does this through active and passive
transport
In homeostasis, everything is PERFECT

16. •Diffusion is the movement of small particles across the
cell membrane like the cell membrane until homeostasis
is reached.
• Facilitated diffusion requires the help of carrier and
channel proteins
These particles move from an area of high concentration
to an area of low concentration.
outside of cell
inside of cell

17. Transport Across Membranes
Passive Transport
Definition: Movement of materials across a
membrane that requires no energy
Subtypes:
1. Simple Diffusion
2. Facilitated Diffusion
3. Osmosis
Active Transport
Definition: Movement of materials across a
concentration gradient that requires energy
and may use carrier proteins
Subtypes:
1. Endocytosis
2. Exocytosis

18. NO ENERGY NEEDED:
Diffusion
Osmosis
Facilitated Diffusion
ENERGY NEEDED:
Active Transport
ANALOGY:

20. Passive Transport: Simple Diffusion
Movement of materials from areas of
high concentration to areas of low
concentration
Passive Transport
Definition: Movement of
materials across a membrane
that requires no energy
Subtypes:
1. Simple Diffusion
2. Facilitated Diffusion
3. Osmosis

21. Passive Transport: Facilitated Diffusion
Movement of sugars and amino
acids driven by transport proteins
Passive Transport
Definition: Movement of
materials across a membrane
that requires no energy
Subtypes:
1. Simple Diffusion
2. Facilitated Diffusion
3. Osmosis
These particles move from an area of high concentration to an area of low concentration.

22. Passive Transport: Osmosis
Movement of WATER from areas of high
concentration to areas of low concentration
Passive Transport
Definition: Movement of
materials across a membrane
that requires no energy
Subtypes:
1. Simple Diffusion
2. Facilitated Diffusion
3. Osmosis

23. Active Transport
Active Transport
Definition: Movement
of materials across a
concentration gradient
that requires energy and
may use carrier proteins

24. Active Transport: The Sodium Potassium Pump
• Cell membrane
typically polarized
• Unequal distribution
of positive and
negative ions
• K+ and Na+ are
redistributed in an
effort to balance the
cell

25. Movement of Large Particles
Endocytosis
Definition: Cell creates vesicle to trap and take
in particle
Exocytosis
Definition: Release of material from the cell

26. Types of Endocytosis
Phagocytosis
Definition: Taking solid substances inside cell
Cell EATING
Pinocytosis
Definition: Taking liquid substances inside cell
Cell DRINKING