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