Exam 2 Part 1 Flashcards
small, non-polar molecules
O2, CO2, N2, steroid hormones
small enough to pass through membrane
small, uncharged polar molecules
H2O, ethanol, glycerol
can pass through membrane, but not very well
larger uncharged polar molecules
amino acids, glucose, nucleosides
very, very small amount can pass through membranes
ions
cannot pass through membranes
membrane transport
simple diffusion, channel-mediated, transport-mediated (active and passive)
transporters
are active or passive -
specific for a certain ion
energy for active transport
ATP
electrochemical gradients
Light
(help regulate the gradients)
passive transport
facilitated diffusion
uses the concentration gradient
passive transport of ions
must account for concentration gradient AND membrane potential
active transport
must couple to something providing free energy
active transport pump types
coupled pump (indirectly uses energy)
ATP-driven pump
Light-driven pump
Na+/K+ pump
active transport
“pay it forward” NEED the electrochem gradient to power other processes
ATP-mediated phosphorylation drives conformation changes
P-type transporter
P-type transporter
Transient ATP-mediated phosphorylation drives conformation changes
transporter types
uniport, symport, antiport
coupled transport
symport and antiports - couples two ions across the membrane -usually using the favorable energy of one ion to help the other across
uniport
1 molecule transported across
glucose in some places
symport
2 molecules transported from the same side
Na+ and glucose
antiport
2 molecules transported from opposite sites
Na+/Ca++
Na+/H+
Glucose/Na+ symport
Indirectly uses Na/K energy -intestine
tight junctions
keeps proteins from interacting and maintains polarity of the epithelial cells
Glucose takeup
Glucose actively transported with Na/glucose symport
facilitatively diffuses across cell
glucose passively pumped into extracellular fluid
ATP-mediated pumps
P-type, V-type, F-type
V-type pump
vesicle pumps
