4. Isolate the cell’s contents from the external envi
ronment
Regulate traffic in and out of the cell
Communicate with other cells
5. The phospholipid bilayer
1. Impermeable to water-soluble and polar molecules, ions
2. Permeable to small and nonpolar molecules
3. Lipids oriented with polar heads facing out
8. Membranes are “fluid mosaics” with proteins e
mbedded in or attached to the membrane
Proteins can move within the fluid lipid bilayer
9. extracellular fluid (outside)
cytoplasm (inside)
protein filaments
recognition protein receptor protein transport protein
binding site
phospholipid
bilayer
phospholipid cholesterol
carbohydrate
10. 1. Transport proteins
◦ regulate the movement of water-soluble molecul
es across the membrane
Ion Channel proteins, Pumps, Receptors
Carrier proteins, Enzymes, Cell adhesion Mol
ecules
11. 2. Receptor Proteins
◦ trigger cellular response when specific mo
lecules bind to them
Nervous system
Endocrine system
12. Passive transport is a function of molecular si
ze, lipid solubility, and size of the concentrati
on gradient
1. Simple diffusion
13. 1 A drop of dye is
placed in water.
2 Dye molecules
diffuse into the
water; water
molecules diffuse
into the dye.
drop of dye
pure water
3 Both dye molecules
and water molecules
are evenly dispersed.
16. (a) isotonic solution (b) hypertonic solution (c) hypotonic solution
10 micrometers
equal movement of water
into and out of cells
net water movement
out of cells
net water movement
into cells
19. (extracellular fluid)
(cytoplasm)
Carrier protein
has binding sit
e for molecule
.
amino acids,
sugars,
small proteins
(c) facilitated diffusion through a carrier
carrier
protein
Molecule enter
s binding site.
Carrier protein changes
shape, transporting molecule
across membrane.
Carrier protein res
mes original shap
24. (extracellular fluid)
Transport protein
binds ATP and Ca
2+.
Transport protein uses e
nergy from ATP to chan
ge shape and move
ion across membrane.
Transport protein
resumes original
shape.
(cytoplasm)
transport protein
ATP bin
ding sit
e
recognition
site
ATP
Ca2+
