Download Chap 5 – Transport Across Membranes

Figure 5.1
CYTOPLASM
Enzymatic
activity
Fibers of
extracellular
matrix (ECM)
Phospholipid
Cholesterol
Cell-cell
recognition
Receptor
Signaling
molecule
Transport
Attachment to the cytoskeleton
and extracellular matrix (ECM)
Signal
transduction
ATP
Intercellular
junctions
Glycoprotein
Microfilaments
of cytoskeleton
CYTOPLASM
Passive transport
 Passive transport = diffusion across cell
membrane
– No energy required!!
– No transport protein required!!!
 Moves WITH concentration gradient
 Examples:
– Urea, CO2, O2, Water, small hydrophobic
Animation: Diffusion
Animation: Membrane Selectivity
© 2012 Pearson Education, Inc.
Figure 5.3A
Molecules of dye
Membrane
Pores
Net diffusion
Net diffusion
Equilibrium
Figure 5.3B
Net diffusion
Net diffusion
Equilibrium
Net diffusion
Net diffusion
Equilibrium
Osmosis =
diffusion of
water
across a
membrane
Lower
Higher
concentration concentration
of solute
of solute
Equal
concentrations
of solute
H2O
Solute
molecule
Selectively
permeable
membrane
Water
molecule
Solute molecule
with cluster of
water molecules
Osmosis
© 2012 Pearson Education, Inc.
Figure 5.5
Hypotonic solution
H2O
Isotonic solution
H2O
H2O
Hypertonic solution
Crenation
H2O
Animal
cell
Normal
Lysed
Plasma
membrane
H2O
H2O
Shriveled
H2O
Plant
cell
Turgid
(normal)
Flaccid
Turgor pressure = pressure of cell membrane
and vacuole against plant cell wall
Shriveled
(plasmolyzed)
plasmolysis
Osmoregulation = Water Balance
 Osmoreguatation = all organisms must regulate
internal water concentrations
– Remove excess water:
– Contractile vacuoles - protists
– Freshwater organisms – kidneys, gills
– Prevent water loss:
– Guard cells in plants (close stomates in leaves to prevent
water loss)
– Kidneys; our skin
© 2012 Pearson Education, Inc.
Video: Chlamydomonas
Video: Plasmolysis
Video: Paramecium Vacuole
Video: Turgid Elodea
Facilitated Diffusion = Passive diffusion of solute
using a transport protein
Solute
molecule
Transport
protein
Only moves solutes with concentration gradient!
Examples: ion channels, aquaporin, GLUT1 (glucose) transporter
5.7 SCIENTIFIC DISCOVERY: Research on
another membrane protein led to the discovery
of aquaporins
 Dr. Peter Agre received the 2003 Nobel Prize in
chemistry for his discovery of aquaporins.
 His research on the Rh protein used in blood
typing led to this discovery.
© 2012 Pearson Education, Inc.
Figure 5.7
Active Transport (using transport protein)
 In active transport, a cell
– must expend energy to
– move a solute against its concentration gradient.
 Primary active transport = ATP used as direct energy source
– Ex: Na-K-ATP Pump
 Secondary active transport = ATP used indirectly
– H+ Pump; Na-Glucose Cotransporter
 The following figures show the four main stages of
active transport.
Animation: Active Transport
© 2012 Pearson Education, Inc.
Figure 5.8_s4
Transport
protein
Solute
1
Solute binding
2
P
ATP
ADP
Phosphate
attaching
P
Protein
changes shape.
3
Transport
Phosphate P
detaches.
4
Protein
reversion
Na-K-ATP Pump
3 Na+ OUTSIDE CELL
Net effect:
High [Na+] built up outside cell
High [K+] built up inside cell
ATP
hydrolysis
2 K+ INSIDE CELL
Na-Glucose Cotransporter
Found in small intestine
3 Na+
OUTSIDE
CELL
Uses potential energy of [Na+]
to drive glucose INTO cell,
against glucose [ ] gradient.
ATP
hydrolysis
2 K+
INSIDE
CELL
Na+ is
allowed to
come
back INTO
cell,
following
its [ ]
Glucose
pumped INTO
cell
H+ Pumps
 Use energy of moving electrons to transport H+
against [ ] gradient
H+ can be pushed AGAINST [ ]
gradient to one side of a membrane
or the other
High energy electrons
ELECTRON SLIDE
Low energy electrons
5.9 Exocytosis and endocytosis transport large
molecules across membranes
 There are three kinds of endocytosis.
1. Phagocytosis = cell eating (cell takes in solids by vesicle)
2. Pinocytosis = cell drinking (cell takes in fluids by vesicle).
3. Receptor-mediated endocytosis receptors on surface
bind molecule and bring in inside cell thru a vesicle.
Animation: Exocytosis and Endocytosis Introduction
Animation: Exocytosis
Animation: Pinocytosis
Animation: Phagocytosis
Animation: Receptor-Mediated Endocytosis
© 2012 Pearson Education, Inc.
Figure 5.9
Phagocytosis
EXTRACELLULAR
FLUID
Pseudopodium
CYTOPLASM
Food
being
ingested
“Food” or
other particle
Food
vacuole
Pinocytosis
Plasma
membrane
Vesicle
Plasma membrane
Receptor-mediated endocytosis
Coat protein
Receptor
Coated
vesicle
Coated
pit
Specific
molecule
Coated
pit
Material bound
to receptor proteins