Post on 25-Dec-2015
Membranes
& Cell Transport
LE 3-1
Bonecell
Smoothmuscle
cell
Ovum Sperm
Neuron inbrain Fat cell
Cells liningintestinal tract
Bloodcells
LE 3-2
Cilia
Cytoplasm
Mitochondrion
Nuclearenvelope
surroundingnucleus
Secretoryvesicles
Plasma (cell)membrane
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
Carbohydratechains
Phospholipidbilayer
Cholesterol
Protein withgated channel CYTOPLASM
Proteins Hydrophilicheads
Cytoskeleton
Proteins
Cellmembrane
Hydrophobic tails
Proteinwith channel
LE 3-5
EXTRACELLULARFLUID
Lipid-soluble molecules, O2 andCO2 diffuse through membranelipids.
Plasma membrane Channelprotein
Largemoleculesthat cannot diffuse throughlipids cannot cross the membraneunless they are transported by acarrier mechanism
CYTOPLASM
Smallwater-solublemolecules andions diffusethroughmembranechannels
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
Watermolecules
Glucosemolecules
A B
Selectively permeable membrane
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).
LE 3-6-2a
Volumedecreased
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.
Volumeincreased
Diffusion & OsmosisAnimations
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 3-7bWater molecules
Hyp0tonic
LE 3-7c
Hypertonic
Solute molecules
Hypertonic
LE 3-8
Glucosemolecule
attaches toreceptor site
EXTRACELLULARFLUID
CYTOPLASM
Receptor site
Carrier protein
Change in shapeof carrier protein
Glucosereleasedinto cytoplasm
LE 3-9
EXTRACELLULAR FLUID
CYTOPLASM
Sodium–potassiumexchange
pump
3 Na+
2 K+ATP ADP
LE 3-10
EXTRACELLULARFLUID
Ligands bindingto receptors
ExocytosisLigand
receptors
CYTOPLASM
Coatedvesicle
Ligands
Endocytosis
Fusion
Lysosome
Fused vesicleand lysosome
Ligandsremoved
Detachment
LE 3-11
EXTRACELLULAR FLUID
Pseudopodium(cytoplasmicextension)
Foreignobject
Vesicle
CYTOPLASM
Undissolvedresidue
LysosomesCell membraneof phagocyticcell
LE 3-12
Microvillus
Microfilaments
Cell membrane
Mitochondrion
IntermediatefilamentsEndoplasmicreticulumSecretoryvesicleMicrotubule
LE 3-14a
Endoplasmic reticulum
Transportvesicle Golgi apparatus Membrane renewal
vesicles
Secretoryvesicles
Lysosomes
CYTOSOL
Vesicleincorporation incell membrane
Cellmembrane
EXTRACELLULARFLUID
LE 3-14b
Exocytosis
Transport TypesAnimations
• http://www.wiley.com/legacy/college/boyer/0470003790/animations/membrane_transport/membrane_transport.htm