lecture 14

Question 1

What is the relationship between dG and concrentrations/voltage potentials across the membrane

Question 2

what are the structure and properties of valinomycin?

Answer 2

Its an ionophore
Its has four subunits
K+ fits perfectly in the middle, peptide carbonyl displaces H2O hydration c=shell

Question 3

what are the structure and properties of ion channels (KcsA)?

Answer 3

Help ions move down gradient
gated, important I transmitting electrical impulse in neurons
has a selectivity filter, a helices with 8 trans membrane helices
backbone carbonyls become crossed when K+ is bound

Question 4

what are the structure and properties of aquaporins?

Answer 4

C4 symmetry
tetramer w 4 2.8 angstrom pores
only H2O can bind via electrostatic repulsion and single-filey

Question 5

what are the structure and properties of glucose transporters (glut 1)?

Answer 5

glut 1 is found in erythrocytes
is either open in or out, no two way
molecule binds in center and causes conformational change

Question 6

transport rates of flux of passive diffusion versus fascilliated diffusion?

Answer 6

facilitated diffusion increases permeability and is highly selective
if all membrane proteins saturated with molecules, transport rate decrease
Passive diffusion has low linear trend
facilitated diffusion increases rapidly then plateaus

Question 7

what are the structure and properties of P-Type ATPase?

Answer 7

bidirectional with ATP hydrolysis
used to maintain Ion gradients
can phosphorylate and lead to a conformational change
example: SERCA (2Ca2+/2H+ out)
NA+/K+ ATPase: 3 NA+ in/2KT out
open out when phosphorylated, open is when dephosphorylated

Question 8

what are the structure and properties of ABC transporters?

Answer 8

ATP bonding domains triggers change from outer->inner state
transports aa, peptides, metal ions, lipids, etc

Question 9

what secondary transport?

Answer 9

One solute moving down its concentration drives another tp move against its concentration

Question 10

difference between symporter and anti porter?

Answer 10

symporter: two molecules move the same way
antiporter: two molecules move in opposite direction

Question 11

what are the structure and properties of GPCRs?

Answer 11

signal amplification and production of second messengers, cAMP, ion channels and phospholipase C

Question 12

what are the structure and properties of receptor tyrosine kinases?

Question 13

What are common features of moving across a membrane?

Answer 13

modularity: adapt to different signals
specificity: specific response to a specific ligans
amplification: one ligand binding event can activate many genes
termination: turning off a signal