Module 5 - Hemoglobin Allostery, Transport Proteins, and Actin-Myosin Flashcards
How does pH compare in the lungs and tissues?
higher in the lungs, lower in tissues
What are the positive and negative allosteric effectors?
positive - oxygen
negative - 2,3-BPG, CO2, and H+
What happens to CO2 in the tissues?
it is hydrolyzed by carbonic anhydrase to form carbonic acid or bicarbonate and H+ (making the tissues more acidic)
What is the Bohr effect?
fractional saturation decreases as CO2/H+ increase and pH decreases
What is 2,3-BPG?
2,3-bisphosphoglycerate binds to hemoglobin and stabilizes the T state by interacting with multiple residues in the center of the tetramer
How does fetal Hb compare to adult, and what impact does this have on oxygen binding?
fetal Hb is a2y2 instead of a2b2. It has lower affinity for 2,3-BPG and therefore shifts toward the R state more often and binds oxygen preferentially to maternal hemoglobin
How does altitude effect O2 binding?
at higher altitudes the body synthesizes more BPG to increase O2 unloading. Even though less O2 binds, the delivery is so much more efficient that the decrease in binding is actually offset/cancelled out.
Describe sickle cell anemia and how it happens. What is one “side effect” of heterozygous sickle cell?
A Glu-Val mutation causes a hydrophobic surface on each hemoglobin where there was not supposed to be one. Therefore, the hemoglobin residues form polymers and sickled red blood cells.
People who are heterozygous for sickle cell appear to be resistant to malaria.
What is oubain?
Na+K+ ATPase transporter proteins are knocked out, results in the heart muscle contracting but not being able to relax to produce another contraction.
What are the two main categories of membrane transport proteins? What are the 4 mechanisms, and how do they differ in rate as solute concentration increases?
passive and active
simple diffusion (passive) increases as solute increases
facilitated diffusion through a channel (passive) increases as solute increase
facilitated diffusion through a carrier (passive) increases hyperbolically and reaches a max when the transporter is saturated
active transport through a carrier (active) increases hyperbolically and reaches a max when the transporter is saturated
What determines is a molecules crosses passively or actively?
if free energy change is negative dG then it can use passive transport, but if the free energy change is positive dG then it requires active transport (ATP must be used to move it)
How can the dG for membrane transport be calculated? What does each variable stand for?
dG = RTln(C2/C1) + ZFdV
R= gas constant
T= temp in K
C2=concentration on the side where it is going (pdt side)
C1=concentration on the side where its coming from (reactant side)
Z=charge of the solute molecule (if zero, then entire term is eliminated)
F=faraday constant, 96.5 kJ/mol
dV=membrane potential across the membrane in volts
What is gramicidin A?
an antibiotic that functions as an ion channel permitting Na+ and K+ to leak out from bacterial cells
What is a porin?
A passive transport protein that share the structure called a B barrel. The hole in the barrel is lined with polar resides while the residues that face the membrane are nonpolar.
Some porins have binding sites for substrate carrier proteins that take cargo to primary active transporters on the inner bacterial membrane.
The Omp32 protein is selective for anions over cations because of many positively charged arginine residues in the channel.
What is a K+ channel protein?
A passive transporter protein that has a selectivity channel. In the channel, carbonyl oxygens provide favorable desolvation energy for K+ ions because they have 8 water molecules but not Na+ ions that only have 6. This results in a 10,000:1 selectivity of K+ over Na+ ions.
