1. Origin of Eukaryotes

2. Cytoplasm (inside of cell)
Membrane Structure
● The plasma membrane separates the living cell from its nonliving surroundings.
(a) Phospholipid bilayer of
membrane
(b) Fluid mosaic model of
Outside of cell
Hydrophilic
head
Hydrophobic
tail
region of
protein
regions of
Phospholipid
bilayer
Proteins
Cytoplasm (inside of cell)

3. Membrane Structure

4. Membrane Structure Phospholipids are amphipathic molecules
● Phospholipid structure
Phospholipids are amphipathic molecules

5. Membrane Structure

6. Membrane Structure
Membrane Models:
1935
Today
*Membranes are fluid

7. Membrane Structure
Membranes are fluid

8. Membrane Structure ● Some functions of membrane proteins
Fibers of
extracellular
matrix
Cytoskeleton
Cytoplasm
Attachment to
cytoskeleton and a b
Cell signaling c d
Enzymatic activity
Transport e
Intercellular
joining f
Cell-cell
recognition
● Cell surface – Extracellular Matrix

9. Membrane Structure

10. Membrane Transport

11. Membrane Transport
Diffusion – a process in which molecules move from an area of high concentration to an area of low concentration
Molecules of dye
Membrane
(a) Passive transport of one type of molecule
Net diffusion
Equilibrium 11

12. Membrane Transport Animal cell H2O H2O H2O H2O Normal Lysing Shriveled
Plasma
membrane
Plant cell
H2O
H2O
H2O
H2O
Flaccid (wilts)
Turgid
Shriveled
(a) Isotonic
solution
(b) Hypotonic
solution
(c) Hypertonic
solution

13. Membrane Transport
Facilitated diffusion

14. Membrane Transport
Active transport requires energy to move molecules across a membrane.
Lower solute concentration
Solute
ATP
Higher solute concentration 14

15. Membrane Transport
*Active transport
Example: sodium-potassium pump

16. Membrane Transport *Voltage *Membrane potential
*Some ion pumps generate voltage across membranes
Electrogenic pump:

17. Membrane Transport
*Each cell membrane has characteristic set of carrier proteins

18. Facilitated diffusion Osmosis Higher solute concentration
MEMBRANE TRANSPORT
Passive Transport
(requires no energy)
Active Transport
(requires energy)
Diffusion
Facilitated diffusion
Osmosis
Higher solute concentration
Higher water concentration
(lower solute concentration)
Higher solute
concentration
Solute
Solute
Solute
Water
Solute
ATP
Lower solute concentration
Lower water concentration
(higher solute concentration)
Lower solute
concentration

19. Traffic of Large Molecules
Exocytosis is the secretion of large molecules within vesicles.
Outside of cell
Plasma
membrane
Cytoplasm 19

20. Traffic of Large Molecules
Endocytosis takes material into a cell within vesicles that bud inward from the plasma membrane. 20

21. Transport of large molecules
Exocytosis
Types of endocytosis found in animal cells:
Endocytosis
*Phagocytosis
*Pinocytosis
*Receptor-mediated endocytosis