Human Function 3 Flashcards
(43 cards)
What is the p50 for Mb and what is it’s significance?
1 atm
Means it has a high affinity for oxygen
Which protein’s oxygen binding curve is hyperbolic?
myoglobin
What is the p50 for Hb?
26 torr
T vs R conformation of Hb
T: not bound by O2, low O2 affinity, more basic
R: bound by O2, high affinity for O2, more acidic
Hb’s sigmoidal curve signifies…
Positive cooperativity (more binding once something is bound) Allosteric effect (one binding communicates with another)
2 reasons for Hb’s lowered O2 affinity
1) curve is a combination of T and R forms
2) 23BPG binds only to T form; stabilizes T form; shifts curve to right
What/where does 23BPG bind?
23BPG is negative, so would want to bind to positive residues
- N term
- hisH+
- lysH+
- 1 on each β subunit (so 6 total)
Why (molecularly) does fetal Hb have a higher affinity to O2 than adult Hb?
There are less + on 23BPG binding site on γ subunit of fwtal Hb; 23BPG binds less tightly to fetal Hb; curve not as shifted to right
Why does a fetus never show signs of sickle cell anemia?
Sickle cell = Glu–> Val on β subunit; fetal Hb does not have β but γ
If you suffer from hypoxia (ex COPD), what can you do to overcome that?
Increase levels of 23BPG so curve shifts right and you lower your oxygen affinity
How is 15-20% of CO2 transported?
Bound covalently to Hb (generates H+)
80-85% of CO2 transported by
blood bicarbonate system (CO2/HCO3-)
Effect of CO2
Binds to T form Stabilizes T form Equilibrium to left Curve shifts right Lower affinity for O2
Effect of H+
Binds to T form of Hb
Pulls equilibrium to left
Shift curve right
Lower O2 affinity
Is there higher [H+] in lungs or tissues?
Tissues
When oxygen is released, does that increase or decrease H+ affinity?
Increase H+ affinity
- shift towards T state which has Hb not bound to O2, and then that Hb can bind to H+
What are the 2 classes of lipids and what are their functions?
- nonpolar: store energy as fat
- polar: cell membrane
Are natural double bonds cis or trans?
Cis
What increases melting point of a fatty acid?
Longer chain
Saturated chain
Structure of triglycerides / triacylglycerol
Glycerol + 3 FA
Structure of glycerophospholipid
Glycerol + phosphate + 2 FA
Structure of phosphatidyl esters
X-phosphate + glycerol + 2 FA
Difference between sphingosine and glycerol
Spingosine:
- amine on C2
- hydrocarbon on C3, not C3OH
Structure of ceramide
Spingosine + palmitate
