1. A. Cell Membrane Structure
1. Phospholipid bilayer
a. hydrophilic heads point out (phosphate)
b. hydrophobic tails in center (fatty acid)
c. not cemented together
d. spaces between
phospholipids can let
things into the cell

2. e) Selective Permeability (membrane selects what gets through)
F) Some molecules sneak between phospholipids and the cell can’t keep them out
i) small - H2O, O2, CO2,
ii) hydrophobic - Lipids)
G) Ions are small but can NOT cross
because they have a charge Na+ Cl-
H) ions and large hydrophilic molecules need help to cross membrane

3. 2. Cholesterol
a. found in animal cells
b. maintains membrane flexibility
c. is a lipid (steroid)

4. 3. Membrane Proteins
a. imbedded in membrane
b. can be tunnels
c. can be pumps

5. Fluid Mosaic Animation

6. B. 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

7. C) Types of Passive Transport all high conc.  low conc.
1) Diffusion
(any molecule, random motion)
2) Facilitated Diffusion
(diffusion through transport protein)
3) Osmosis
(diffusion of water through membrane)

8. Diffusion

9. Facilitated Diffusion
Molecules too big to fit btwn phospholipids
must go through transport protein

10. Osmosis
Diffusion of water
must cross a membrane

11. D) Types of Active Transport can be low conc.  high conc.
1) Protein pumps
(transport protein pushes molecules
against conc. gradient)
2) exocytosis
(cell membrane spits out molecules)
3) endocytosis
(cell membrane takes in molecules)

12. Protein Pumps
Protein pushes molecules into areas where they are in high concentration.
ATP is the
energy used

15. E) Terms for solute concentrations
substance dissolved in water (sugar)
2) Hypertonic solution =
high concentration
of solute
3) Hypotonic solution =
lower concentration

16. 4) Isotonic solutions =
same concentration of solute
if mol. can pass through membrane….
they will do so until equal conc. on each side

18. F) Homeostasis
1) homeostasis = maintaining a constant environment in your body
2) keeping cells in an isotonic solution =
major part of homoeostasis.