1. Cell Membrane Strucutre
1. Phospholipid bilayer
a. hydrophilic heads point out (phosphate)
b. hydrophobic tails in center (fatty acid)
c. amphipathic (both philic and phobic)
c. held together by hydrophobic interactions
d. capable of
rapid lateral movement

2. Selective Permeability
A) Molecules can pass through membrane phospholipids on their own
i) small or non-polar (H2O, O2, CO2, Lipids)
ii) Large polar molecules get through only
very slowly (glucose) or via transport proteins
iii) ions seldom cross on their own
B) More rapid transport requires proteins

3. Cell Membrane Structure
2. Cholesterol
a. found in animal cells
b. maintains membrane fluidity
1. high temp restrains p-lipid movement
2. low temp:
prevents
close packing

4. Cell Membrane Structure
3. Membrane Proteins
a. Integral (penetrate into CM)
some are transmembrane
b. Peripheral
May be held in
Place by cytoskeleton
Or ECM
(Extracellular
matrix)

5. Membrane Proteins (p97) 1. Membrane Enzymes a. often grouped in teams
b. active in metabolism
c. bind to cytoplasmic substrates

6. Membrane Proteins 2. Attachment proteins a. bind to ECM
b. bind to cytoskeleton
c. maintain cell shape and location
d. non-covalent bonds

7. Membrane Proteins 3. Recognition proteins/lipids
a. sort cells in embryo
b. immune system self-recognition
c. often glycoproteins (glycolipids)
d. differ between species, individuals, cell types
e. A B O blood types

8. Membrane Proteins 4. Intercellular Joining a. gap junctions
b. adhering junctions

9. Membrane Proteins 5. Receptor Protiens aid Signal Transduction
a. receptors – bind to chemical messenger
(hormones, cAMP)
b. binding signal molecule changes protein shape
c. signals inside of cell by binding cytoplasmic protein causing transduction

10. Receptor Protein example

11. G protein example

12. Membrane Proteins 6. Transport proteins
a. channel proteins (aquaporin)
b. carrier proteins (glucose transporter &
protein pumps)
c. all are specific

13. 2 Types of Cellular Transport
1) Passive Transport = no energy needed
mol. flow high concentration  low conc.
2) Active Transport =
takes energy
molecules pumped
Low conc.  high conc.
Exocytosis/endocytosis

14. 3 Types of Passive Transport all high conc.  low conc. due to…
a) potential energy of concentration gradient
b) thermal energy causing Brownian motion .
1) Diffusion
(any molecule, random motion)
2) Facilitated Diffusion
(diffusion through channel protein)
3) Osmosis
(diffusion of water through membrane)

15. 1. Diffusion
Dynamic equilibrium = no net movement

16. 2. Facilitated Diffusion
Molecules too big /polar / charged
must go through transport protein. Either
Channel protein or carrier protein
(aquaporin) (glucose carrier)
Some channel proteins gated

17. 3. Osmosis
Diffusion of water
must cross a membrane

18. Tonicity =
Ability of surrounding solution to make a specific cell gain or lose water
No net movement =
isotonic (same solute)
Water moves into cell =
hypotonic solution (less solute in solution)
Water moves out =
hypertonic solution (more solute in solution)

21. Osmoregulation
Control of solute and water concentrations inside a cell
Contractile vacuoles
aquaporin

22. Diffusion Rates Affected by:
1. concentration
2. size of molecule
3. temperature
4. electric gradient
5. pressure gradient
6. # pores

23. 3 Types of Active Transport can be low conc.  high conc.
All require energy input
Pumps move individual molecules
Endo/exocytosis do ‘bulk transport’

24. 1. Protein Pumps Transport proteins that require energy
Protein pushes molecules into areas where they are in high concentration.
ATP is the
energy used
Proton pumps
Pump H+ ions

25. 2. Exocytosis How cells secrete materials like hormones
a. transport vesicle buds from
golgi body
b. vesicle moved to C.M. by motor protein
c. vesicle fuses with CM
d. contents spill out into extracellular space

27. Endocytosis Cell takes in molecules by forming new vesicles at CM
a. phagocytosis = takes in food
b. pinocytosis = takes in water
c. receptor mediated = triggered by molecule binding to membrane receptor
* helps concentrate rare molecules