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MLS Heme Lec 11
| Question | Answer |
|---|---|
| Where does globin chain synthesis occur and what what cell stages are involved | RBC ribosome pronormoblast to reticulocyte |
| Globin chain synthesis is directed by | 8 genetic loci per haploid genome |
| How many types of globin chains are produced by genes and what are the names | 7, Zeta, Epsilon, Gamma-A, Gamma-G, Delta, Beta, and Alpha |
| What processes are involved for DNA replication | transcription, translation, and codons |
| Location of genes | Chromosome 16= Zeta (embryonnic), Alpha Chromosome 11= Epsilon (embryonic), Gamma, Delta, Beta |
| Activation of globin genes progress from | Zeta to Alpha on chromosome 16 Epsilon to gamma, delta, beta on chromosome 11 |
| Which chains only appear during embryonic development | epsilon and zeta chains, produced up to 3 month following conception |
| Once produced, which chain is always present | alpha |
| Embryonic hemoglobin | hemoglobin gower 1 (zeta2, epsilon2) hemoglobin gower 2 (alpha2, epsilon2) hemoglobin portland (zeta2, gamma 2) |
| Production of gamma chains is active from what point and which hemoglobin is it | third fetal month until 1 yr postnatally fetal hemoglobin (alpha2, gamma2) |
| By age 2 how much fetal hemoglobin is left | <2% |
| What occurs postnatally between 3 and 6 months | beta chain rises gradually and reaches adult percentages |
| What is the shape of normal adult hemoglobin | tetramer consisting of 2 alpha chains 2 non-alpha chains- beta, delta, or gamma hydrogen bonds and salt bridges |
| Alpha2, Beta2 -hemoglobin A- is found in what percentage in both adults and newborns | 95-97% Adult 30% Newborn |
| Alpha2, Delta2 -hemoglobinA2- percentage in both adults and newborns | 2-3% Adult 1% Newborn |
| Alpha2, Gamma2 -hemoglobinF- percetage for both adults and newborns | 1-2% Adult 70% Newborn |
| Hemoglobin production | 1. heme is inserted into globin chains 2. amino acids become twisted in a helical shape and coil like a pretsel 3. comprises 33% of cell (2.8 million hemoglobin molecules/RBC) |
| If amino acid sequence changes what can happen | the hemoglobin will not coil and the red cell is no longer pliable |
| Hemoglobin function | delivery and release of oxygen to tissue facilitation of carbon dioxide excretion |
| One of the most important controls of hemoglobin affinity for oxygen is | RBC organic phosphate 2,3-diphosphoglycerate (2,3-DPG) Produced in the Leubering-Rapaport Shunt |
| Deoxyhemoglobin | hemoglobin when 2,3-BPG is present |
| Describe hemoglobin when 2,3-BPG is present | it widens the space between the beta chains, forming an anionic salt bridge |
| Oxyhemoglobin | occurs in the lung, hemoglobin when 2,3-BPG is absent |
| Describe hemoglobin when 2,3-BPG is absent | the salt bridge is broken and the hemoglobin will carry more oxygen |
| Salt bridge in doxyhemoglobin causes | a lower affinity for oxygen |
| Absent salt bridge in oxyhemoglobin causes | beta chains to be pulled together which expels 2,3-BPG |
| Hemoglobin affinity for oxygen determines the | proportion of oxygen that is released to the tissues or loaded onto the cell at a given oxygen pressure (PO2) |
| Increased oxygen affinity | hemoglobin has a high affinity for oxygen, does not readily give up oxygen (in lungs) |
| Decreased oxygen affinity | hemoglobin has a low affinity for oxygen, releases oxygen more readily |
| Oxygen affinity for hemoglobin is usually expressed as | PO2 at which 50% of the hemoglobin is saturated with oxygen (P50) |
| P50 is normally | 26 mm Hg |
| Hemoglobin-Oxygen Dissociation Curve | sigmoid curve that results from hemoglobin-oxygen saturation is plotted vs partial pressure of oxygen (PO2) |
| PO2 | partial pressure of oxygen |
| Hemoglobin-Oxygen Dissociation Curve description | a physiological curve shape of a curve permits a considerable amount of oxygen to be delivered to the tissues with a small drop of oxygen tension |
| What is the oxygen tension in the lungs | near 100 mm Hg 100% saturated |
| As RBCs circulate, oxygen is released when | PO2 drops to 40 mm Hg 25% of oxygen is released at this point |
| P50 occurs around | 22 mm Hg |
| Right shift in curve | Hypoxia- reduction of oxygen supply to tissues Increased 2,3-BPG Anemia Acidosis Fever |
| Oxygen affinity is decreased | more oxygen is released to the tissues |
| Decreased oxygen delivered to the tissues causes a oxygen tension drop | 12% is released at 40mm Hg |
| Left shift in a curve | Decreased 2,3-BPG Alkalosis Increased quantity of abnormal Hgb Multiple transfusions Fetal hemoglobin- red cells have high affinity for oxygen |
| During a Left Shift | pH increases Temperature decreases 2,3-BPG decreases |
| During a Right Shift | pH decreases Temperature increases 2,3-BPG increases |
| Acquired Nonfunctional Hemoglobins | hemoglobin molecules have been altered |
| Altered hemoglobin causes | compromised oxygen transport and consequences |
| Hypoxia | inadequate amount of oxygen at tissue level |
| Cyanosis | bluish color of skin due to presence of high amounts of deoxyhemoglobin in blood |
| 3 nonfunctional hemoglobins | Carboxyhemoglobin Methemoglobin Sulhemoglobin |
| Carboxyhemoglobin | occurs when hemoglobin is exposed to carbon monoxide, can be fatal |
| Hemoglobins affinity for carbon monoxide vs oxygen is | >200 times greater than affinity of oxygen |
| Smokers can have a carbon monoxide level up to | 12% |
| Methemoglobin | hemoglobin with iron in the ferric (+3) state |
| Methemoglobin is incapable of | binding to oxygen |
| Increased levels of methemoglobin are formed | when exposed to certain oxidizing drugs or chemicals |
| What age group is more susceptible to methemoglobin production | Infants, HbF more readily converts |
| Sulfhemoglobin | Irreversible change in hemoglobin molecule |
| Sulfhemoglobin structure | Sulfur atom combines with each of the four heme groups and binds to the oxygen |
| Sulfhemoglobin affinity for oxygen vs hemoglobin | 1/100 |
| Senescence | cell aging |
| Aging is characterized by | Decline in glycolytic enzyme which decreases ATP production |
| During aging the cell loses the ability to | Maintain shape Deformability Membrane integrity |
| Senescence results in what type of cells | Spherocyte Rigid Burr |
| What removes senescent cells | macrophages of the RE system |
| Transferrin returns | iron to the BM or liver where it is stored as ferritin |
| Globin is broken down into | amino acids and recycled |
| Protoporphyrin ring breaks down into | toxic bilirubin which is carried to the liver by albumin |
| Where and why is bilirubin conjugated | In the liver to make is more soluble and excretable |
| What is conjugated bilirubin converted into and why | Urobilinogen by bacteria which is then excreted in the stool and a small amount in the kidney |
| 90% of extravascular erythrocyte destruction takes place in the | Spleen Liver Bone Marrow or Histocytes |
| 10% of erythrocyte destruction is intravascular and results from | RBC hemolysis |
| RBC hemolysis | RBC ruptures in the blood vessels and hemoglobin is released directly into the bloodstream |
| RBC lifespan | 120 days |
| Function of haptoglobin | Picks up the alpha & beta dimers from ruptured RBC and takes them to the liver |
| How does haptoglobin prevent kidney damage | Becomes a larger molecule that cannot be excreted by the kidney |
| The dimers are converted to | bilirubin |
| Percent of RBCs removed daily | 1% |
| The 1% is replaced by | Reticulocytes from the bone marrow pool |
| What analysis is performed on a blood smear | 100 cell differential of WBC RBC morphology examined Platelet estimation performed |
Created by:
mlrlemons
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