Resp - Physio (Hemoglobin & Oxygen) Flashcards
Pg. 597-598 in First Aid 2014 Sections include: -Hemoglobin -Hemoglobin modifications -Oxygen-hemoglobin dissociation curve -Oxygen content of blood
What are the components of Hemoglobin?
Hemoglobin (Hb) is composed of 4 polypeptide subunits (2 alpa and 2 beta)
How many forms of (normal adult) Hemoglobin are there, what are they, and what distinguishes/defines each?
Exists in 2 forms: (1) T (taut) form has low affinity for O2 (2) R (relaxed) form has high affinity for O2.
What kind of cooperativity and allostery does Hb exhibit?
Hb exhibits positive cooperativity and negative allostery.
What 5 conditions favor taut over relaxed form of Hb? What effects does this have?
Increased (1) Cl- (2) H+ (3) CO2 (4) 2,3-BPG and (5) temperature favor taut form over relaxed form (shifts dissociation curve to right, leading to increased O2 unloading)
Where are the taut versus relaxed forms of Hb found in the body?
Taut in Tissues, Relaxed in Respiratory Tract
How does Fetal Hb differ from adult Hb in terms of structure?
Fetal Hb (2 alpha and 2 gamma subunits); (adult) Hemoglobin (Hb) is composed of 4 polypeptide subunits (2 alpa and 2 beta)
How does Fetal Hb differ from adult Hb in terms of affinity?
Fetal Hb (2 alpha and 2 gamma subunits) has lower affinity for 2,3-BPG than adult Hb and thus has higher affinity for O2
In general, what is the effect of hemoglobin modifications?
Lead to tissue hypoxia from decreased saturation and decreased O2 content
What is Methemoglobinemia? What distinguishes it from normal hemoglobin in terms of function?
Oxidized form of Hb (ferric, Fe3+) that does not bind O2 as readily, but has increased affinity for cyanide
What is the normal state of iron in Hb?
Iron in Hb is normally in a reduced state (ferrous, Fe2+); Think: “just the 2 of US: ferroUS is Fe2+”
What are 2 ways that Methemoglobinemia may present?
Methemoglobinemia may present with cyanosis and chocolate-colored blood
How is cyanide poisoning treated, and why?
To treat cyanide poisoning, use nitrites to oxidize Hb to methemoglobin, which binds cyanide. Use thiosulfate to bind this cyanide, forming thiocyanate, which is renally excreted.
How can Methemoglobinemia be treated?
Methemoglobinemia can be treated with methylene blue.
How do nitrites cause poisoning?
Nitrites cause poisoning by oxidizing Fe2+ to Fe3+
What is Carboxyhemoglobin? What distinguishes it from normal hemoglobin in terms of function?
Form of Hb bound to CO in place of O2. Causes decreased oxygen-binding capacity with a left shift in the oxygen-hemoglobin dissociation curve. Decreased O2 unloading in tissues.
What change does Carboxyhemoglobin cause to the oxygen-hemoglobin dissociation curve? What change does it have in the tissues?
Causes decreased oxygen-binding capacity with a left shift in the oxygen-hemoglobin dissociation curve. Decreased O2 unloading in tissues.
What is the shape of the oxygen-hemoglobin dissociation curve, and why?
Sigmoidal shape due to positive cooperativity (i.e., tetrameric Hb molecule can bind O2 molecules and has higher affinity for each subsequent O2 molecule bound).
How does the oxygen-myoglobin dissociation curve differ from the oxygen-hemoglobin one?
Myoglobin is monomeric and thus does not show positive cooperativity; curve lacks sigmoidal appearance
What occurs with a shift to the right on the oxygen-hemoglobin dissociation curve?
When curve shifts to the right, decrease affinity of Hb for O2 (facilitates unloading of O2 to tissue).
What factors cause shifts of the oxygen-hemoglobin dissociation curve, and what conditions cause which shifts?
Think: “BAT ACE: BPG (2,3-BPG), Altitude, Temperature, Acid, CO2, Exercise; An increase in all factors (including H+) causes a shift of the curve to the right; A decrease in all factors causes a shift of the curve to the left
What shift on the oxygen-hemoglobin dissociation curve does Fetal Hb cause, and why?
Fetal Hb has a higher affinity for O2 than adult Hb, so its dissociation curve is shifted left.
Graph the oxygen-hemoglobin dissociation curve, including myoglobin and normal blood curves. On the normal blood curve, label oxygenated blood leaving the lungs versus blood returning from tissues.
See p. 598 in First Aid 2014 for first graph
Graph normal blood versus 50% CO Hb in terms of pCO2 in mmHg (x axis) and O2 bound to Hb in mL O2/100 mL (y axis).
See p. 598 in First Aid 2014 for second graph
Define O2 content.
O2 content = (O2 binding capacity x % saturation) + dissolved O2
How much O2 can 1 g of Hb normally bind?
Normally 1 g Hb can bind 1.34 mL O2
What is the normal Hb amount in blood?
Normal Hb amount in blood is 15 g/dL
Under what condition does cyanosis result?
Cyanosis results when deoxygenated Hb > 5 g/dL
What is the typical value for O2 binding capacity?
O2 binding capacity ~ 20.1 mL O2/dL
Which of the following factors decrease as Hb falls: O2 content of arterial blood, O2 saturation, arterial PO2.
O2 content of arterial blood decreases as Hb falls, but O2 saturation and arterial PO2 do not
What is the equation for O2 delivery to tissues?
O2 delivery to tissues = cardiac output x O2 content of blood
What changes (if any) to the following measurements occur with CO poisoning: (1) Hb level (2) % O2 sat of Hb (3) Dissolved O2 (PaO2) (4) Total O2 content?
(1) Normal (2) Decreased (CO competes with O2) (3) Normal (4) Decreased
What changes (if any) to the following measurements occur with Anemia: (1) Hb level (2) % O2 sat of Hb (3) Dissolved O2 (PaO2) (4) Total O2 content?
(1) Decreased (2) Normal (3) Normal (4) Decreased
What changes (if any) to the following measurements occur with Polycythemia: (1) Hb level (2) % O2 sat of Hb (3) Dissolved O2 (PaO2) (4) Total O2 content?
(1) Increased (2) Normal (3) Normal (4) Increased
