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Erythrocyte Biochemistry Flashcards

1
Q

Hemoglobin is made via ____ before extrusion of their nucleus

A

Normablast

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2
Q

List the events of O2 Binding to Heme

A

1) Fe2+ = out of plane 2) O2 Binds and brings Fe2+ into plane 3) Proximal F8 Histidine pulled down 4) Distal Histidine Stabilizes and Provides hydrogen bonds

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3
Q

Myoglobin has a ___ curve

A

Hyperbolic

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4
Q

Hemoglobin has a __ curve

A

Sigmoidal

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5
Q

Describe Positive Cooperativity

A

1) O2 binds to heme and facilitates more binding

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6
Q

How does exercise influence O2 delivery

A

1) Decreases PO2 in tissues –> more efficient delivery ** Remember O2 wants to go from high to low

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7
Q

What is 2,3 BPG made by? How does it have an effect on oxygen delivery?

A

Metabolizing Tissues Promotes delivery of O2 to Tissues

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8
Q

What is the Bohr Effect?

A

Lower pH –> better oxygen delivery

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9
Q

Discuss how 2,3 BPG has an effect on HbF and HbA

A

2,3 BPG effects HbA but not HbF –> HbF increased affinity for O2 vs mother

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10
Q

Describe the Sickle Cell Anemia Mutation

A

1) Position 6
2) Glutamic Acid (-) to Valine (hydrophobic)

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11
Q

What are the two storage forms of Iron?

A

1) Ferritin
2) Hemosiderin

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12
Q

What is hemosiderin

A

Iron Storage Complex that is composed of partially digested ferritin and lysosome

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13
Q

How does Fe2+ get into cell

A

Diffusion through membrane

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14
Q

How does Fe3+ get into cell?

A

1) Converted to Fe2+ via Duodenal Cytochrome B (Ferric Reductase) with aid of Vit. C
2) Fe 2+ enters via DMT1
3) To fates
- Storage: Converted to Fe3+ via Ferroxidase (cerruloplasmin) –> Ferritin
- Transported to blood via Ferroportin

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15
Q

What transports iron to the target tissues?

A

Transferrin

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16
Q

Starting with Fe2+ entering blood via Ferroportin, describe how iron gets to target tissues.

A

1) Fe2+ converted to Fe3+ via Ferroxidase
2) Fe3+ binds Transferrin
3) Transferrin binds TfR
4) Complex is internalized via clathrin mediated endocytosis
5) Complex is in Endosome –> decrease pH
6) Releases Transferrin from TfR
7) Endosome docks mitochondria and transfers iron to mito via DMT1

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17
Q

How does iron get into the mitochondria? (Channel)

A

DMT1

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18
Q

Ferroportin requires ___

A

Hephaestin

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19
Q

What negatively regulates Ferroportin?

A

Hepcidin

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20
Q

Nonheme iron is converted to Fe2+ via ___. What does this enzyme require?

A

1) Duodenal Cytochrome B (Ferric Reductase)
2) Vitamin C

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21
Q

When Hepcidin binds ferroportin what occurs?

A

Internalization and degradation via Lysosomes

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22
Q

What regulates Hepcidin (3x)

A

Transferrin

Hepcidin Receptor

HFE (Human Homeostatic Iron Regulatior Protien)

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23
Q

What is Hypochromic Microcytic Anemia caused by?

A

Iron Def.

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24
Q

How would you teat Hypochromic Microcytic Anemia ?

A

Dietary Supplement

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25
Characterize Hypochromic Microcytic Anemia
Small Pale RBC w/ decreased hemoglobin
26
What is Hereditary Hemochromotosis or HH)
Iron Overload
27
What Mutation occurs in Hereditary Hemochromatosis?
HFE (Hereditary hemochromatosis gene)
28
Where is iron accumlated in HH?
1) Heart --\> Heart Failure 2) Liver --\> Cirrhosis and Hepatocellular Carcinoma 3) Pancreas --\> Diabetes
29
What is the active form of folate?
THF
30
Folate is reduced to DHF via what? (This is also the same enzyme that is reduces DHF to THF)
Dihydrofolate Reductase
31
Function of Folate
DNA synthesis (Purines and Pyrimidine Thymine)
32
Def. Folate causes ....
Decreased DNA synthesis --\> Megaloblastic Macrocytic Anemia
33
Where is Folate Absorbed
SI
34
Where is Folate stored?
Liver
35
Folic acid is converted to ___ when absorbed which is the primary circulating form.
N5-methyl-THF
36
How does N5-methyl-THF convert to THF?
Vit. B12
37
What is the job of Vit B12 in converting N5-methyl-THF?
Transfers Methyl Group
38
What is the dietary form of folate?
DHF
39
Function of Methotrexate
Antineoplastic agent and inhibitor of DNA Synthesis
40
What enzyme does Methotrexate inhibit
Dihydrofolate Reductase
41
Another name for Vit B12
Cobalamine
42
How do humans get Vit. B12
Animal products
43
Where is Vit. B12 absorbed?
Ileum via Intrinsic Factor
44
How is the Intrinsic Factor - Vit. B12 complex carried through the blood?
Transcobalamin II
45
How is Intrinsic Factor - B12 complex taken up by cells
Receptor Mediated Endocytosis
46
Pernicious anemia is caused by
Def. B12
47
Pernicious Anemia is normally caused by \_\_\_
Destruction of Gastric Mucosa
48
Total Serum Folate and Serum B12 in Pernicious Anemia
1) Folate: \<3ng/mL 2) \< 350pg/mL
49
Schilling Test importance
Determining cause of PErnicious Anemia
50
How is Schilling Test Formed
Radioactive B12 ingested
51
if Radioactive B12 present in urine what does that mean
Normal Absoprtion and Pernicious Anemia due to B12 Deficient Diet
52
Location of Biosynthesis opf Heme
Liver and Erythroid cells of bone marrow
53
Where does Heme Production occur with in the cell?
Mitochondria and Cytosol
54
How many Phases are in Heme Biosynthesis? List their Location as well with in cell.
1) Phase I: Mitochondria 2) Phase 2: Cytosol 3) Phase 3) Mitochondria
55
Describe the Rxn in Phase I in Heme biosynthesis.
Rxn: Glycine + Succinyl CoA --\> d-aminolevulinic acid (ALA) Enzyme: ALA Synthase (Vit B6)
56
What is the end product of Phase I
ALA
57
What is the goal of Phase II of heme biosynthesis
Coproporphyrinogen III Generation
58
List the rxns of Phase 2 without the enzymes added
RXN: 1) 2x ALA --\> Phorphobilinogen (PBG) 2) Porphobilinogen --\> Hydroxymethylbilane 3) Hydroxymethlybilane --\> Uroporphyrinogen 4) Coproporphyrinogen Generation
59
Function of ALA Synthase, ALA Dehydratase, and Porphobilinogen Deaminase
1) ALA Synthase: Glycine + Succinyl CoA --\> ALA 2) ALA Dehydratase: 2x ALA --\> Porphobilinogen (PBG) 3) Porphobilinogen Deaminase: Porphobilinogen --\> Hydroxymethylbilane
60
What is the Goal of Phase III?
Generation of Protoporphyrin and introduction of iron to form heme
61
How does Protoporphyrin IX get converted into heme in Phase II of heme biosynthesis
Ferrochelatase
62
What does ALA synthase require
Vit B6 (Pyridoxial Phosphate)
63
What occure with Vit B6 def. (3x)
Heme Syntesis is deminished RBCs are pale Ironstore increase
64
What are the two Isoforms of ALA Synthase
ALAS I (Ubiquitous) ALAS II (Erythroid Cells)
65
ALAS I and ALAS II are inhibited by... (2x)
1) Heme 2) Hemin
66
ALAS II increases its transcription and translation in the presence of \_\_\_
Iron
67
Lead Poisoning: Lead inhibits what two enzymes?
1) ALA Dehydratase (contains Zn) and Ferrochelatase (Contains Fe)
68
Lead Poisoning: If ALA Dehydratase is inhibited then what would you expect to see in the patient?
1) Increased ALA 2) Neurotoxicity and Neurological Symptoms due to ALA being a Neurotoxin
69
Lead Poisoning Effects: 4x
1) Neurological Symptoms 2) Decreased Heme Production 3) Prescence of Hypochromic Microcytic anemia 4) impacted ATP and Energy Metabolism
70
What are Porphyrins?
Inherrited Metabolic Disorders with defects in heme synthesis
71
What are the two categories of Porphyrins. Describe symptoms.
1) Actue Hepatic: Neurological 2) Erythropoietic: Skin and Photosensirivity
72
Congenital Erythropoietic Porphyrin Cause
Defective Uroporphrinogen III Synthase (Erythrocytes)
73
Symptoms of Congenital Erythropoietic Porphyrin
1) Photosensitivity 2) Red Color Urine and teeth 3) Hemolytic Anemia
74
Results of Congenital Erythropoietic Porphyrin
1) Increased Uroprophyrinogen I and its red color - Air oxidation production of urporphyrin I
75
Cause of Celebrity Porphyrias (Varigate Porphyrin)
Protoporphyrinogen IX oxidase Def.
76
Symptoms of Celebrity Porphyrias (Varigate Porphyrin)
1) Photosensitivity 2) Neurological Symptoms 3) Developmental Delay in Children 4) Hallucinations, Delulsions, Convulsions
77
What system is heme degraded by?
Reticulo-endothelial system
78
Describe Heme Degradation RXN and Enzymes
RXN: Heme (Porphyrin Ring) --\> Biliverdin --\> Bilirubin (Tetrapyrrole Ring) Enzymes: -----Heme Oxygenase + O2--\> Biliverdin + CO -----Biliverdin Reductase + NADPH
79
Heme Oxygenase reduces Ferrous iron to \_\_\_\_
Ferric
80
What is the rate limiting step in Conjugation of Bilirubin
UDP Glucuronyl Transferase
81
How is Bilirubin and Albumin Complex removed from blood
Liver Uptake
82
Mechanism of BR Conjugation
1) UDP-Glucose Dehydrogenase: UDP Glucose --\> UDP-Glucuronate 2) Bilirubin EDP Glucuronyltransferase: 2UDP-glucuronate + Bilituin IXa --\> Bilirubin Diglucuronide
83
Why is Bilirubin Congugated?
B/C its insouble and needs to be converted to be safely excreted
84
List the steps in heme degradation
1) Heme oxygenase: Coverts Heme to Biliverdin (green pigment) 2) Biliverdin Reductase: Biliverdin --\> Bilirubin 3) Bilirubin complexed w/ albumin released to blood 4) Congugation occurs in liver and released into gall bladder 5) SI microbes reduce Bilirubin to urobilinogen 6) Two Fates of Urobilinogen - Resorbed and converted to Urobilin via kidneys - Further Microbe reduction to Stercobilin (found in feces)
85
Jaundice is cause by \_\_\_
Hyperbilrubinemia
86
3 Types of Jaundice
1) Pre Hepatic 2) Intra Hepatic 3) Post Hepatic
87
What type of BR is increased in Pre Hepatic Jaundice
Unconjugated
88
Cause of Pre Hepatic Jaundice (2x)
Excess Hemolysis due to hemolytic Diseases Internal Hemmorage
89
Glucose 6-P dehydrogenase Def. causes __ Jaundice
Pre Hepatic
90
Intrahepatic Jaundice is due to
Impaired hepatic uptake, conjugation, or secretion of conjugated BR
91
Disease Examples associated with Intra Hepatic jaundice
1) Criggler - Najjar Syndrome 2) Gilberts Syndrome
92
Post Hepatic Jaudice is caused by (3x)
1) Obstruction to biliary tree 2) Cholangiocarcinoma 3) Gall Stones
93
What type of BR is increased in Post Hepatic Jaundice
Conjugated
94
Relative lab values and symptoms of Post Hepatic Jaundice
1) Increased blood conjugated BR 2) Dark Urine 3) Pale Stool (No Sterobilin) 4) Increased Alkaline Phosphate (ALP)
95
UDP- GT- Related Disorders:
1) Type I Criggler - Najjar Syndrome 2) Type II Criggler - Najjar Syndrome 3) Gilberts
96
Cause for Type I Criggler
Complete Absence of UDP-GT gene
97
Results of Type I Criggler
1) Severe Hyperbilirubinemia - Accumulates in brains of babies --\> encephelopathy (Kernicturus)
98
Type II Criggler cause
Mutant UDP GT gene (enzyme has 10% activity)
99
Cause of gilberts Syndrome
Reduced activity of UDP-GT (25% activity)
100
What is Hepatitis
Inflammation of liver leading to liver dysfunction
101
What type of BR is elevated in hepatitis?
Unconjugated and Conjugated
102
Causes of hepatitis (3x)
1) Viral Infections 2) Alcoholic Cirrhosis 3) Liver Cancer
103
Symptoms of Hepatitis due to BR accumulation
1) Yellow Discoloration of skin and sclera 2) Dark, Tea colored Urin
104
List the Colors of Bruises and their culprit
1) Red - Heme 2) Green - Biliverdin 3) Orange - Bilirubin 4) Reddish Brown - Hemosiderin
105
Cause of Neonatal (Physiologic) Jaundice
Unable to conjugate and excrete bilirubin due to UDP-GT def.
106
Treatment of Neonatal Jaundice (2X)
Phototherapy Inhibition of Heme Oxygenase
107

CPR (18 decks)

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