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Biochem > Heme > Flashcards

Heme Flashcards

1
Q

Carbon Monoxide Poisoning

A

Carbon monoxide binds tightly but reversible to iron hemoglobin.

  • replaces oxygen
  • traps hemoglobin in relaxed form
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2
Q

how does carbon monoxide poisoning look on a graph?

A
  • shifts saturation curve to HYPERBOLA

- oxygen is not released in tissue

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3
Q

Embryonic Hemoglobin has a higher affinity to oxygen than HbA due to what? and what is the significance of this feature?

A

weak binding of 2,3 BPG by HbF

-facilitates transfer of oxygen across placenta from mother to fetus

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4
Q

alpha gene family

A

occurs at chromosome 16 on a single chromosome.

-diploid has 4 copies of 2 active genes.

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5
Q

Beta gene chromosome

A

occurs at chromosome 11

-1 copy of beta gene and diploid 2 copies.

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6
Q

How does goblin gene expression occur and where?

A

in RBC precursors
Transcription->
splicing->translation into globin protein

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7
Q

Alpha Hemoglobin stabilizing protein (AHSP)

A

binds and stabilizes excess alpha hemoglobin

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8
Q

Sickle Cell Disease.

what type of point mutation, AA and location of mutation

A

autosomal, recessive disorder

  • point mutation in beta globin
  • GAG to GTG
  • leads to a single AA change 6th position of hemoglobin beta protein val to glu
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9
Q

Sickle Cell Disease. What does the HbS fibers do to erythrocte. What is the role of microinfarcts?

A

HbS form fibers distorting erythrocyte.

  • elongated erythocytes occlude blood flow in capillaries.
  • microinfarcts produce tissue anoxia resulting in severe pain.
  • increase susceptibility to infections, acute chest syndrome, stroke, splenic and renal dysfunction
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10
Q

What is the selective disadvantage of sickle cell disease?

A

heterozygotes are less susceptible to malaria.

-shorter life span for RBCs prevent P. falciparum from completing its life cycle

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11
Q

Hemoglobin C Disease. where does point mutation occur? what type of AA?

A

Point mutation in beta globin gene.

-leads to single amino acid change in 6th position of hemoglobin beta protein glu to lys.

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12
Q

What happens to homozygous individuals that have hemoglobin C disease?

A
  • mild, chronic hemolytic anemia.
  • No infarctive crises
  • no treatment necessary
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13
Q

Hemoglobin SC disease. what happens to beta globin chains?

A

beta globin chains carry HbS and some carry HbC mutations

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14
Q

methenoglobinemia

A 
contains ferric (3+) instead of ferrous (Fe2+)
-methemoglobin can't bind oxygen
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15
Q

in methenoglobinemia what are the causes when methemoglobin can’t bind oxygen?

A
  • oxidation of iron by drugs (nitrates)
  • deficiency of NADH-cytochrome B5 reductase
  • (NADH methemglobin reductase reduces Fe3+ to Fe2+)
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16
Q

Thalassemias

A

imbalance in synthesis of globin chain.

-reduced rate of production of one globin

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17
Q

alpha thalassemias

A

4 alpha globins
-one altered gene for globin (silent)
-2 alter gene: alpha t. trait
-3 altered genes: HbH disease with mild hemolytic anemia
4 altered: hydrops fetaliz: causes fetal death

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18
Q

beta thalassemias

A

altered expression in thalassemias trait (minor)

2 altered: majpr

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19
Q

What are the storage proteins and what do they carry?

A

Albumin: carry protein

transferrin: transport ferric iron
ferritin: iron storage protein

20
Q

Albumin transports

A

divalent( Ca2+) and trivalent cations (Fe3+)

  • hydrophobic molecules: fatty acids, sterols, bilirubin
  • drugs: penicilin and warfarin etc.
21
Q

Hemosiderin

A

derivative of Ferritin used to store iron in liver, spleen and bone marrow
-insoluble in aq solution

22
Q

ceruloplasmin

A

transports copper (Cu2+) liver to peripheral tissue

  • regulates iron transport
  • increase in cerulosplasmin concentration is observed in liver disease and tissue damage
23
Q

wilson’s disease

A

low ceruloplasmin
elevated serum copper
elevated excretion of urine
metabolic defect is in excretion of copper in bile and its reabsorption in kidney

24
Q

Myoglobin describe the structure and the AA within

A
  • 150 AA
  • 8 alpha helixes (a-H)
  • AA with NP inside
  • AA charged groups at the surface
  • bound to Heme
25
Q

Heme structrue

A

-protoprophyrin IX and ferrous (Fe 2+) iron
-prosthetic group: non protein factor needed for enzyme activity. covalently attached enzyme
-iron forms 6 bonds
four with N of protoporphyrin

26
Q

Heme binds with

A
  • one proximal histidine to F helix

- oxygen stabilized by distal histidine

27
Q

What happens to the structure of hemoglobin when oxygen binds in hemoglobin?

A

iron moves to plane of hemoglobin

28
Q

What are the functions of Heme

A
  • carries oxygen of hemoglobin and myoglobin
  • carries electrons for redox reactions and cytochrome
  • breaks down hydrogen peroxide
29
Q

Hemoglobin A

A

carries oxygen, CO2 and protons.

found in RBCs

30
Q

What is the structure of Hemoglobin? What type of bonds attach to subunits?

A

heteroteramer:
2 alpha chains,2 beta chains
-subunits attach by hydrophobic interactions

31
Q

How do alpha and beta dimers interact?

A

hydrophobic and ionic interaction

32
Q

-dimers interact through

A

ionic and hydrogen bonds

33
Q

Tense or taut form has what type of infinity?

A

deoxygenated form -low oxygen affinity

34
Q

Relaxed form

A

oxygenated form, high oxygen affinity

35
Q

Hemoglobin exhibits __. What does the term mean? What is the shape of curve

A

Cooperatively: as one oxygen binds, the affinity for another oxygen is increased.
-sigmodal dissociation curve

36
Q

Hemogloblins affinity for the 4th oxygen is how many more times than the first 1?

A

300x

37
Q

What does the dissociation curve is steepest at the oxygen concentrations that occur in where?

A

Tissues. allows oxygen delivery to respond to small changes in pO2

38
Q

Oxygen binding hemoglobin is Allosterically effected by and release of oxygen is enhanced how?

A

pH: released of oxygen is enhanced by decreasing pH
pCO2:release of Oxygen is enhanced by increase C02
2,3-BPG

39
Q

2,3-BPG

A

synthesized from intermediate in glycolysis.

-stabilizes taut form of Hb

40
Q

What is the Bohr effect and Give example.

A

increase in [H+] lowers that affinity of hemoglobin for oxygen.
Ex: pH 7.6 in alveoli of lungs has a higher affinity than tissues pH (7.2)

41
Q

CO2 + H2O -> H2CO3

A

carbonic anhydrase catalyzes the formation of carbonic acid from carbon dioxide and water.

42
Q

H2CO3 -> HCO3- + H+

A

carbonic acid spontaneously dissociates into bicarbonate and a proton.

43
Q

Some CO2 binds to hemoglobin as___.

A

carbamate: (carbamino-hemoglobin)

44
Q

What is the structure for Heme

A

-Protoporphyrin IX and ferrous (Fe2+) iron
-Prosthetic group
-Iron forms 6 bonds
Four with N of protoporphyrin

45
Q

Prosthetic group

A

nonprotein factor needed for enzyme activity

-covalently attached to enzyme (not dissociable)

46
Q

What is the structure of hemoglobin?

A
  • Its a heterotetramer.

- 2 alpha and 2 beta chains attached by hydrophobic interactions

Biochem (7 decks)

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