Hydrophilic
head
WATER
Hydrophobic
tail
WATER
1
Phospholipid
bilayer
Hydrophobic regions
of protein
Hydrophilic
regions of protein
2
TECHNIQUE
RESULTS
Extracellular
layer
Proteins
Inside of extracellular layer
Knife
Plasma membrane
Cytoplasmic layer
Inside of cytoplasmic layer
3
Lateral movement
Flip-flop
(~107 times per second)
(~ once per month)
(a) Movement of phospholipids
Fluid
Unsaturated hydrocarbon
tails with kinks
Viscous
Saturated hydrocarbon tails
(b) Membrane fluidity
Cholesterol
(c) Cholesterol within the animal cell membrane
4
Membrane proteins
Mouse cell
Mixed proteins
after 1 hour
Human cell
Hybrid cell
5
Fibers of
extracellular
matrix (ECM)
Glycoprotein
Carbohydrate
Glycolipid
EXTRACELLULAR
SIDE OF
MEMBRANE
Cholesterol
Microfilaments
of cytoskeleton
Peripheral
proteins
Integral
protein
CYTOPLASMIC SIDE
OF MEMBRANE
6
EXTRACELLULAR
SIDE
N-terminus
C-terminus
CYTOPLASMIC
SIDE
α Helix
7
Signaling molecule
Enzymes
ATP
(a) Transport
Receptor
Signal transduction
(b) Enzymatic activity
(c) Signal transduction
(e) Intercellular joining
(f) Attachment to
the cytoskeleton
and extracellular
matrix (ECM)
Glycoprotein
(d) Cell-cell recognition
8
ER
1
Transmembrane
glycoproteins
Secretory
protein
Glycolipid
Golgi
2
apparatus
Vesicle
3
4
Secreted
protein
Plasma membrane:
Cytoplasmic face
Extracellular face
Transmembrane
glycoprotein
Membrane glycolipid
9
Molecules of dye
Membrane (cross section)
WATER
Net diffusion
Net diffusion
Equilibrium
(a) Diffusion of one solute
Net diffusion
Net diffusion
Net diffusion
Net diffusion
Equilibrium
Equilibrium
(b) Diffusion of two solutes
10
Lower
concentration
of solute (sugar)
Higher
concentration
of sugar
Same concentration
of sugar
H2O
Selectively
permeable
membrane
Osmosis
11
Hypotonic solution
H2O
Isotonic solution
H2O
H2O
Hypertonic solution
H2O
(a) Animal
cell
Lysed
H2O
Normal
H2O
Shriveled
H2O
H2O
(b) Plant
cell
Turgid (normal)
Flaccid
Plasmolyzed
12
50 µm
Filling vacuole (a) A contractile vacuole fills with fluid that enters from
a system of canals radiating throughout the cytoplasm.
Contracting vacuole
(b) When full, the vacuole and canals contract, expelling
fluid from the cell.
13
EXTRACELLULAR
FLUID Channel protein
Solute
CYTOPLASM
(a) A channel protein
Carrier protein
Solute
(b) A carrier protein
14
EXTRACELLULAR
FLUID
[Na+] high
[K+] low
Na+
Na+
Na+
Na+
Na+
Na+
Na+
Na+
CYTOPLASM
Na+
[Na+] low
[K+] high
P
ADP
2
1
ATP P
3
K+
K+
K+
K+
K+
P
K+
6
5
Passive transport 4
P
15
Active transport
ATP
Diffusion
Facilitated diffusion 16
–
–
ATP
EXTRACELLULAR
FLUID +
+
H+ H+ Proton pump
H+ –
+
–
CYTOPLASM
H+ H+ +
–
+
H+ 17
–
+
ATP
–
H+
H+
+
Proton pump H+
–
H+
H+
+
–
+
Sucrose-H+
cotransporter H+
H+
Diffusion
of H+
H+
Sucrose
–
–
+
+
Sucrose
18
PHAGOCYTOSIS 1 µm
EXTRACELLULAR
CYTOPLASM
FLUID Pseudopodium Pseudopodium
of amoeba “Food”or
other particle
Bacterium
Food
vacuole Food vacuole
An amoeba engulfing a bacterium
via phagocytosis (TEM) PINOCYTOSIS
0.5 µm Plasma
membrane
Pinocytosis vesicles
forming (arrows) in
a cell lining a small
blood vessel (TEM) Vesicle RECEPTOR-MEDIATED ENDOCYTOSIS Coat protein
Receptor
Coated
vesicle
Coated
pit Ligand A coated pit
and a coated
vesicle formed
during
receptormediated
endocytosis
(TEMs) Coat
protein
Plasma
membrane
0.25 µm 19