Download 03a_plasma membrane

Membranes
& Cell Transport
LE 3-1
Cells lining
intestinal tract
Blood
cells
Smooth
muscle
cell
Ovum
Bone
cell
Sperm
Neuron in
brain
Fat cell
LE 3-2
Cilia
Secretory
vesicles
Cytoplasm
Mitochondrion
Plasma (cell)
membrane
Nuclear
envelope
surrounding
nucleus
Chromatin (DNA)
What do membranes do?
•Form the boundary between the intracellular
compartment and the extracellular environment.
•“Traffic Cop” - Regulate what enters and leaves the
cell = “selective permeability.”
•Respond to substances that come in contact with
the membrane. Ex: insulin, glucagon, & other
hormones
•Secrete (=squeeze out) substances that are synthesized
inside the cell.
•Compartmentalize and organize the interior of the cell.
Ex: mitochondria, E.R., various vesicles
Early evidence for the bi-layered structure of the plasma membrane
came from transmission electron micrographs.
This is the plasma membrane of a RBC.
A phospholipid bilayer –
This is NOT a functional
membrane
Here is a detailed
picture of the way
six phospholipid
molecules interact
with each other
and their
surroundings to
form a
phospholipid
bilayer.
Phospholipid Animation
(Click Here)
LE 3-3
EXTRACELLULAR FLUID
Carbohydrate
chains
Phospholipid Protein
bilayer with channel
Hydrophobic
tails
Proteins
Cell
membrane
Cholesterol
Protein with
gated channel
Proteins Hydrophilic
heads
Cytoskeleton
CYTOPLASM
LE 3-5
EXTRACELLULAR
FLUID
Lipid-soluble molecules, O2 and
CO2 diffuse through membrane
lipids.
Plasma membrane
Large
CYTOPLASM
molecules
that cannot diffuse through
lipids cannot cross the membrane
unless they are transported by a
carrier mechanism
Channel
protein
Small
water-soluble
molecules and
ions diffuse
through
membrane
channels
LE 3-4
Diffusion = spreading of molecules from a
place where the concentration [ ] is higher to
a place where it’s lower.
OSMOSIS = diffusion of
H2O, across a membrane,
from a region of higher
[H2O] to a region of lower
[H2O].
“[ ]” means “concentration of…”
Gray dots represent solute particles. Solute
= anything dissolved in the water.
LE 3-6-1
Two solutions containing different
solute concentrations are separated by
a selectively permeable membrane.
Water molecules (small blue dots)
begin to cross the membrane toward
solution B, the solution with the higher
concentration of solutes (larger pink
circles).
A
B
Water
molecules
Glucose
molecules
Selectively permeable membrane
LE 3-6-2a
At equilibrium, the solute
concentrations on the two sides of
the membrane are equal. The volume
of solution B has increased at the
expense of that of solution A.
Volume
increased
Volume
decreased
Diffusion & Osmosis
Animations
http://www.biologycorner.com/bio1/diffusion.html
http://www.tvdsb.on.ca/westmin/science/sbi3a1/Cells/Osmosis.htm
http://www.stolaf.edu/people/giannini/flashanimat/transport/osmosis.swf
LE 3-7a
Isotonic
Water molecules
LE 3-7b
Hyp0tonic
Water molecules
LE 3-7c
Solute molecules
Hypertonic
Hypertonic
LE 3-8
Glucose
molecule
attaches to
receptor site
EXTRACELLULAR
FLUID
Change in shape
of carrier protein
Receptor site
Carrier protein
CYTOPLASM
Glucose
released
into cytoplasm
LE 3-9
EXTRACELLULAR FLUID
3 Na+
Sodium–
potassium
exchange
pump
2 K+
ATP
ADP
CYTOPLASM
LE 3-10
EXTRACELLULAR
FLUID
Ligands binding
to receptors
Ligands
Endocytosis
Exocytosis
Ligand
receptors
CYTOPLASM
Coated
vesicle
Lysosome
Ligands
removed
Fused vesicle
and lysosome
LE 3-11
Cell membrane
of phagocytic
cell
Lysosomes
Vesicle
Foreign
object
Pseudopodium
(cytoplasmic
extension)
EXTRACELLULAR FLUID
CYTOPLASM
Undissolved
residue
LE 3-12
Microvillus
Microfilaments
Cell membrane
Mitochondrion
Intermediate
filaments
Endoplasmic
reticulum
Secretory
vesicle
Microtubule
LE 3-14a
Endoplasmic reticulum
EXTRACELLULAR
CYTOSOL FLUID
Lysosomes
Cell
membrane
Secretory
vesicles
Transport
vesicle
Golgi apparatus
Membrane renewal
vesicles
Vesicle
incorporation in
cell membrane
LE 3-14b
Exocytosis
Transport Types
Animations
• http://www.wiley.com/legacy/college/boyer/04
70003790/animations/membrane_transport/me
mbrane_transport.htm