Hemoglobin Flashcards
What does Hepcidin do?
It inhibits Fe transport from mucosal cell. Because Fe levels are too high.
What is HbF vs HbA.
Fetal hemoglobin (small amount of adults still have). Adult hemoglobin (most prevalent type in adults).
What is hemoglobin comprised of? Explain chains, bonds, etc.
It is made of 4 proteins: 2 alpha-beta dimers. Each dimer is made of globin chains, which can each attach a heme prosthetic group. So there are 4 heme per Hb. Each chain is bonded by hydrophobic interactions while the dimers are held together by ionic bonds.
What is transferrin? What is it’s relationship to apotranserrin?
It carries Fe in the blood and delivers it to cells via receptor-mediated endocytosis. Apotransferrin is transferrin when unbound by Fe.
What does bilirubin glucuronyl transferase do?
It conjugates bilirubin into 2 molecules that are then transported into bile. All of which occurs during heme degradation.
Why is buildup of iron or heme bad?
The buildup of free iron=heme is bad because pathogens like free iron. This can cause infection. Also, buildup of heme in the body makes reactive O2 species, which can hurt membranes.
What is the significance of the sigmoidal shape of the O2 Dissociation Curve? List 2 answers.
- The curve shows how hemoglobin is responsive to small changes in the partial pressure of O2, or the concentration of O2 in the tissues. It is not as responsive to small changes in the lungs. This allows for efficient unloading in the tissues.
- The curve also suggests allosteric regulation.
What is the Bohr Effect?
This is the idea that if hydrogen ions are increased in the tissues, or acidity is increased, then the equation: Hb + 4O2 Hb(O2)4 + nH+ , is shifted to the left and more O2 is released. Thus, the affinity for O2 has decreased. So H+ is a type of negative effector molecule/allosteric inhibitor for hemoglobin.
What does carbonic anhydrase do?
This enzyme uses CO2 and H20 to produce the bicarbonate ion in RBC.
What are the negative effector molecules/allosteric inhibitors that affect hemoglobin?
1) 2,3-Bisphospoglycerate (2,3-BPG)
2) H+ (hydrogen ions)
3) CO2
4) Temperature
5) Microenvironment of exercising muscle
What is cooperative binding and how does it affect hemoglobin?
Cooperative binding is the binding of molecule A onto a site of molecule B and the induced affect A has on another site of B. When O2 is bound to hemoglobin, Fe is pulled in and there is no more puckering. Additionally, there is added strain. The strain is released when Hb goes from the T to R form and the movement of globin chains is transferred to other chains on the Hb unit. This transfer causes future binding of O2 onto these other chains to be easier. In other words, O2 affinity is increased with each successive binding of O2.
What are the T and R forms of Hemoglobin?
The T form stands for tight or taut. It has a lot of ionic bonds and is the deoxygenated form of Hb. And it has a low affinity for O2. The R form is the relaxed form. It has few ionic bonds and is bound by O2, and thus has a high affinity for O2. Transition between these forms (T to R) allows for cooperative binding.
What are 2 kinds of Porphyrias? What is it a defect of?
It is a defect in heme synthesis.
- Acute Intermittent Porphyria: asymptomatic unless precipitating factors
- Porphyria cutanea tarda: chronic, photosensitive, people with alcoholism or liver damage
What is thalassemia? And what is the different between the alpha and beta forms?
Thalassemia is a hemoglobinopathy in which there is a partial or total loss of globin chains. Alpha Thalassemia has one or more globin genes deleted. Beta Thalassemia has an accumulation of precipitation of alpha chains that causes hemolysis and anemia
What is the difference between Bart’s Syndrome and Hemoglobin H disease?
Bart’s syndrome is characterized by a deletion of 4 alpha globin genes while Hemoglobin H disease has a deletion of 3 alpha genes.
