Download - 5.6 Facilitated Diffusion
5.6 Facilitated Diffusion
• Type of passive transport (no energy!)• High to low concentration
• For molecules that cannot diffuse across the membrane on their own.
• Transport proteins are used
5.6 Facilitated Diffusion
– Transport proteins are specific for the substrate,
– The substrate can be sugars, amino acids, ions, and even water
5.6 Facilitated Diffusion
• Channel Protein: becomes a hydrophilic tunnel for passage
5.6 Facilitated Diffusion– Carrier protein: binds to its passenger, changes
its shape, and releases its passenger on the other side
5.7 TALKING ABOUT SCIENCE: Auquaporins
• Peter Agre researched membrane proteins • Led to discovery of aquaporins
5.7 TALKING ABOUT SCIENCE:
Auquaporins
– Aquaporin: allows for rapid diffusion of water into and out of cells (plant cells, kidney cells, RBCs)
5.8 Active Transport
• Cells have a mechanism for moving a solute against its concentration gradient
– Requires energy (ATP)
– The mechanism alters the shape of the membrane protein through phosphorylation using ATP
Transportprotein
Solute
Solute binding1
Transportprotein
Solute
Solute binding1 Phosphorylation2
Transportprotein
Solute
Solute binding1 Phosphorylation2 Transport3
Proteinchanges shape
Transportprotein
Solute
Solute binding1 Phosphorylation2 Transport3
Proteinchanges shape
Protein reversion4
Phosphatedetaches
5.8 Active Transport
• Cells actively transport Ca2+ out of the cell.• Is calcium more concentrated inside or outside of
the cell?
5.8 Active Transport
5.9 Exocytosis
– used to export bulky molecules, such as proteins or polysaccharides
• material to be transported is packaged within a vesicle that fuses with the membrane
• Example: the excretion of insulin by cells within the pancreas into the bloodstream
5.9 Endocytosis
– used to import substances useful to the livelihood of the cell
• material to be transported is packaged within a vesicle that fuses with the membrane
• There are 3 kinds of endocytosis
Phagocytosis
EXTRACELLULARFLUID
Pseudopodium
CYTOPLASM
Foodvacuole
“Food” orother particle
Foodbeingingested
Phagocytosis:
– engulfment of a solid particle by wrapping cell membrane around it, forming a vacuole
Pinocytosis
Plasmamembrane
Vesicle
Plasma membrane
Pinocytosis
– is the same thing except that fluids are taken into small vesicles
Coatedvesicle
Coatedpit
Specificmolecule
Receptor-mediated endocytosis
Coat proteinReceptor
Coatedpit
Material boundto receptor proteins
Plasma membrane
Receptor-mediated endocytosis
– is where receptors in a receptor-coated pit interact with a specific protein, initiating formation of a vesicle
