The document summarizes the fluid mosaic model of cell membranes. It describes how phospholipids form a bilayer that acts as a fluid "lake" in which various proteins are embedded or float. This bilayer allows for selective permeability and passive diffusion of small molecules through the membrane. The document also discusses different types of membrane proteins, mechanisms of passive and active transport, and large molecule transport via endocytosis and exocytosis.

1. Chapter 6 – Cell Membranes

2. Fluid Mosaic Model
Phospholipids form a bilayer which is like a
“lake” in which a variety of proteins “float.”

3. Phospholipids Bilayer
Forms Spontaneously in water
Vary in fatty acid chain length, degree of saturation, and phosphate
groups
Membranes may be up to 25 percent cholesterol
Flexible allowing lateral movement
of molecules
Fluidity depends on temperature
and lipid composition.

4. Components of the Fluid
Mosaic Model
• Lipids
– Phospholipids/ Cholesterol
• Proteins
– Intergral
– Peripheral
• Carbohydrates

5. Membrane Bounds Proteins
Two types of membrane proteins:
• Peripheral membrane proteins lack
exposed hydrophobic groups and do
not penetrate the bilayer.
• Integral membrane proteins have
hydrophobic and hydrophilic regions
or domains.

6. Transmembrane Proteins
• Type of integral
protein
• Extend all the way
through the
phospholipid
bilayer.

7. Selective Permeability
Some substances can Passive transport:
pass through, but not no outside energy
others required (diffusion).
What can pass:
- Small Active transport:
- Uncharged energy required
Examples?

8. Diffusion
The process of
random movement
toward equilibrium
It is the net movement
from regions of
greater concentration
to regions of lesser
concentration.

9. What Controls the Speed of
Diffusion?
- Diameter of the molecules or ions
- Temperature of the solution
- Concentration Gradient
- Electrochemical Gradient
- When a cell is involved you also have
to consider movement across a
membrane.

10. Simple Diffusion
Small molecules pass directly through
the lipid bilayer.
Water and lipid-soluble molecules can
diffuse across the membrane.
Electrically charged and polar molecules
can NOT pass through easily.

11. Osmosis
The Diffusion of Water
Osmosis depends on the number of
solute particles present, not the type of
particles.

12. Hypertonic Solutions: High
Solute Concentrations
Cell Shrinks

13. Hypotonic Solutions: Low
Solute Concentrations
Cell Lyses in Animal Cells
Swells in Plant Cells (Turgor Pressure)

14. Isotonic Solutions: Equal
solute/water concentration
Cell Remains the Same

15. Facilitated Diffusion
Passive Transport across a membrane using
an integral membrane protein
Channel proteins: have a central pore lined
with polar amino acids.
Carrier proteins: membrane proteins that bind
some substances and speed their diffusion
through the bilayer.

16. Channel Proteins
Specificity
Best Example are
Ion Channels
Most are “Gated”
Ligand-Gated Rate and direction of ion movement
through channels depends on the
concentration gradient and the
distribution of electrical charge.
Voltage Gated

17. Membrane Potential
A charge imbalance across a membrane.
Represents lots of potential energy
Signals volatge-gated channels to open
Critical to ATP production during Cellular
Respiration or Photosynthesis

18. Carrier Proteins
Passive Transport
Directly binds to
molecule
Then Changes shape
to move the
molecule across the
membrane

19. Active Transport
Require Energy
Move molecules
AGAINST the
concentration gradient
Uniporters
Symporters
Antiporters

20. Large Molecule Transport
Endocytosis: bring Exocytosis: Move
material into the cell material out of the cell
using vesicles using vesicles

21. Endocytosis
3 TYPES
Phagocytosis: Engulf
large molecules or even
whole cells making
hagosomes
Pinocytosis: Cellular
Drinking (small vesicles)
Receptor Mediated
Endocytosis: binds
specific targets