hemoglobin Flashcards
hemoglobin (hb) is composed of
4 polypeptide subunits
2α and 2β
1 heme in every polypeptide
hemoglobin (hb) is exists in how many and which forms
2 forms
T form and R form
hemoglobin (hb) - T form properties
Taut form
deoxygenated
low affinity for 02
hemoglobin (hb) - R form properties
Relaxed
oxygenated
high affinity for 02 (X300)
hemoglobin (hb) - properties
- positive cooperativity
2. negative allostery
hemoglobin (hb) - positive cooperativity
tetrameric Hb molecule can bind 4 02 molecules and has higher affinity for each subsequent O2 molecule bound
substance that favor taut form over relaxed form (shift curve to right)
INCREASED CL-, H+, CO2, 2,3-BPG, TEMPERATURE
fetal hemoglobin subunits
2α and 2γ
fetal hemoglobin vs adult (about function)
loewer affinity for 2,3-BPG than adult hemoblobin and thus higher affinity for O2
hemoglobin aslo act as
a buffer for H+ ions
buffer for H+ ions
hemoglobin
hemoglobin modifications - types
- methemoglobin
2. carboxyhemoglobin
hemoglobin modifications lead to
tissue hypoxia from decreased O2 saturation and decreased 02 content
hemoglobin - normal iron status
resuced state Fe2+
FERROUS
ferrous hemoglobin
Fe2+
ferric hemoglobin
Fe3+
methemoglobin
oxidized form of Hb (ferric, F3+)
methemoglobin vs normal hemoglobin - iron status
normal: resuced state Fe2+ (FERROUS)
methemoglobin: oxidized state Fe3+ (FERRIC)
methemoglobin properties
- it does not bind 02 as readily
- it has increased affinity for cyanide
methoglobinemia may present with
- cyanosis 2. chocolate-colored blood
methoglobinemia can can be treated with
- methylene blue
2. vitamin C
how to treat cyanide poisoning (and the mechanism)
nitrites followed by thiosulfate
nitrites: hemoglobin –> methoglobin which bind cyanide
thiosulfate: to bind cyanide, forming thiocyanate , which is renally excreted
methoglobinemia may be used
to treat cyanide poisoning
substance that cause poisoning by oxidizing F2+ to F3+ (found in)
- nitrites (from dieaary intake or polluted/high altitude water)
- benzocaine
benzocaine poisoning
F2+ to F3+
nitrites poisoning
F2+ to F3+
methylene blue is used to
treat methoglobinemia
carboxyhemoglobin
form of hemoglobin bound to CO in place of o2
CO binds to Hb in the place of …
O2
carboxyhemoglobin causes
decreased oxygen binding capacity with left shift in oxygen hemoglobin dissociation curve
carboxyhemoglobin effect on curve
left shift in oxygen in oxygen-hemoglobun (and decreased plateau)
carboxyhemoglobin causes in tissues
decreased O2 unloading in tissues
CO vs O2 on Hb
CO binds competitively to Hb and with 200X greater affinity than
carboxyhemoglobinemia treatment
100% 02 and hyperbaric 02
how to treat methemoglobinemia
methylene blue
oxygen-hemoglobin dissociation curve -shape and why
sigmoidal shape due to positive cooperativity
Myoglobin - structure, properties
Myoglobin monomeric and thus does not show positive cooperativity
Myoglobin - oxygen-hemoglobin dissociation curve
curves lacks sigmoidal appearance
right shift of oxygen-hemoglobin dissociation curve causes
decreased affinity of Hb for O2
right shift oxygen-hemoglobin dissociation curve - purpose
facilitates unloading of 02 to tissue
oxygen-hemoglobin dissociation curve with fetal hemoglobin and mechanism
Fetal Hb has higher affinity for 02 than adult Hb, so its dissociation curve is shifted left
oxygen-hemoglobin dissociation curve shift factors
- H+ 2. CO2 3. Exercise 4. 2,3-BPG
- Altitude 6. Temperature
increased –> right shift
decreased –> left shift
02 content =
equation
O2 content = (O2 binding capacity x saturation) + disolved O2 = (1.34xHbxSaO2) + (0.003xPaO2) SaO2=arterial 02 saturation PaO2=partial pressure of 02 (0.003xPaO2) = dissolved oxygen (1.34xHb) = oxygen binding capacity
normally 1 g Hb bind …. 02
1.34 ml
normal amount of Hb in blood
15g/dL
cyanosis results when
deoxygenated Hb > 5 g/dL
02 binding capacity (calculation and result)
O2 binging capacity = normal amount of Hb in blood x 1.34 ml = 15g/dL X 1.34ml = 20.1 ml 02/dL
02 binding capacity (result) (normally)
20.1 ml 02/dL
decreased Hd –> O2 content of arterial blood?
decreased
decreased Hd –> O2 saturation?
no change
decreased Hd –> arterial PO2?
no change
02 delivered to tissues (equation)
02 delivered to tissues = cardiac output x O2 contain of blood
CO poisoning - Hb concentration?
normal
anemia - Hb concentration?
decreased
polycythemia - Hb concentration?
increased
CO poisoning - % saturation of Hd?
decreased
anemia - % saturation of Hd?
normal
polycythemia - % saturation of Hd?
NORMAL
CO poisoning - dissolved O2 (PaO2)?
normal
anemia - dissolved O2 (PaO2)?
normal
polycythemia - dissolved O2 (PaO2)?
normal
CO poisoning - total 02 content?
decreased
anemia - total 02 content?
decreased
polycythemia - total 02 content?
increased
polycythemia - % saturation of Hd?
NORMAL
CO vs O2 binding on Hb (affinity?)
CO has x200 greater affinity
Dissolved O2 in blood - equation
0.003 x PaO2