Porphyrins and Hemoglobin Flashcards
(116 cards)
1
Q
chemical intermediates of hemoglobin, myoglobin,
cytochromes, and enzymes (catalase and peroxidase)
A
Porphyrins
2
Q
What causes red color of hemoglobin?
A
presence of alternating double bonds of porphyrins allows the structure to absorb light
3
Q
All porphyrins are macrocyclic structures consisting of a _________ ring linked by______ bridges.
A
tetrapyrrole, methyl
4
Q
Porphyrins also fluoresce reddish-pink at ____ nm
A
400
5
Q
Four ____ atoms chelate metal atoms (usually iron, competes with zinc)
▪ Iron chelates with protoporhyrin IX to form heme
A
Nitrogen
6
Q
Iron in heme can also bind to globin proteins to form ________ &
____________.
A
HEMOGLOBIN &
MYOGLOBIN
7
Q
fights against reactive oxygen species
A
catalase
8
Q
hemoglobin, myoglobin, and
cytochromes all contain…
A
heme
9
Q
Heme synthesis occurs in all cells, but primarily
____________(erythroidprecursors) and ______.
A
bone marrow, liver
10
Q
Iron chelates with ________________ to form heme
A
protoporhyrin IX
11
Q
Enzymes in heme synthesis localized in…
A
mitochondria and cytoplasm
12
Q
what are the Mitochondrial enzymes involved with heme synthesis?
A
1) ALA synthase, 2) copropophyinogen oxidase, 3)
protoporhyrinoghen oxidase, and 4) ferriochelatase
13
Q
What are the Cytoplasmic enzymes involved with heme synthesis?
A
1) ALA dehydrogenase, 2) PBG deaminase, 3)
Uroporphyrinogen III synthetase, and 4) Uroporphyrinoghen decarboxylase
14
Q
ALA & PBG are ________soluble
A
water
15
Q
precursors to porphyrins
A
▪ Porphyrinogens
16
Q
these spontaneously oxidize (with light oxygen or oxidizing agents) to form three major porphyrins:
A
Porphyrinogens
17
Q
three major porphyrins…
A
- Uroporphyrin [URO]: excreted in urine
- Coproporphyrin [CORPO]: excreted in urine and/or feces
- Protoporphyrin [PROTO]: excreted in feces
18
Q
porphyrin that is excreated in urine?
A
Uroporphyrin [URO]
19
Q
porphyrin excreted in urine and/or feces
A
Coproporphyrin [CORPO]
20
Q
porphyrin that is excreted in feces?
A
Protoporphyrin [PROTO]
21
Q
▪Porphyria can be inherited or caused by…
A
drugs, liver disease, anemias, or toxic
metals that cause disturbances in heme synthesis and porphyrin metabolism
22
Q
How many enzymes are involved in heme synthesis?
A
8
Deficiency in seven of the eight enzymes involved in heme synthesis
! Leading to a distinct form of porphyria
23
Q
Lack of enzyme activity –> decrease in formation and excretion of porphyrin or
accumulation of its __________.
A
precursors
24
Q
Symptoms of Neurological porphyria?
A
Constipation, nausea, vomiting, severe
abdominal pain, tachycardia, hypertension,
sweating and urinary retention,
*neurotoxicity, psychiatric disturbances,
Cutaneous lesions, hyperpigmentation
25
Neurological porphyria:
Acute disturbances of porphyrin synthesis that allow accumulation of early precursors (____ and _____)
ALA, PBG
26
excess accumulation of all three porphyrias may cause...
photosensitivity, cutaneous lesions, and hyperpigmentation
27
As porphyrin molecules absorb light in
skin, electrons become excited and
eventually decay to ground state
-transferring energy to molecular oxygen
-activated oxygen species
Cutaneous porphyria
28
If ALA and PBG are elevated it is mostly likely what type of porphyria?
neurological porphyria
29
What type of porphyria causes the most skin damage?
protoporphyrin (not secreted in urine)
30
-Most common porphyria
-barbiturates and sulfonamides
-increased Urinary ALA, PBG, URO
Acute intermittent porphyria
31
Urine may turn red or black after exposure to air due to spontaneous polymerization
of PBG to porphyrin
Urine may turn red or black after exposure to air due to spontaneous polymerization
of PBG to porphyrin
32
NO photosensitivity with Acute intermittent porphyria, why?
URO won’t be accumulated in the tissue
33
Variegate porphyria is due to issues with what enzyme?
protopophyrinogen oxidase
34
major symptom of Variegate porphyria?
Photosensitivity
35
Urine: ALA URO; Feces: PROTO, COPRO
Variegate porphyria:
36
Photosensitivity, but less than Variegated porphyria
Hereditary coproporphyria
37
Urine: ALA, URO; Feces: COPRO
Hereditary coproporphyria
38
Porphyria cutanea tarda is due to an issue with what enzyme?
uroporphyrinogen decarboxylase
39
Hepatoerythropoietic porphyria
Porphyria cutanea tarda
40
Feces: Isocoproporphyrine, Urine:URO
Porphyria cutanea tarda
41
Protoporphyria is an issue with what enzyme?
Ferrochelatase (partial)
42
RBC, plasma, feces: PROTO, Urine: normal porphyrin
Erythropietic Protoporphyria
Protoporphyria
43
Congenital erythropoietic porphyria is due to an issue with what enzyme?
Uroporphyrinogen III synthase
44
Feces: porphyrins (Corpo, prorp), RBC, urine: increased URO I and COPRO I
Congenital erythropoietic porphyria
45
Erythrodontia (reddish-brown discoloring of teeth):
Disfigurement and tendency to avoid daylight
Erythrodontia (reddish-brown discoloring of teeth):
Disfigurement and tendency to avoid daylight
46
Unknown enzyme defect, probably coproporphyrinogen
oxidase
Erythropoietic coproporphyria
47
increased RBC coproporphyrin & fecal COPRO (key finding )
Erythropoietic coproporphyria
48
acquired porphyria (secondary disorders) are a result of...
toxins or drugs
49
How is acquired porphyria distinguished from true porphyrias?
only urinary ALA excretion is increased
but PBG remains normal.
50
Lead poisoning inhibits....
inhibits ALA dehydratase and ferrochelatase
51
clinically presents with increased RBC Zn-protoporphyrins and increased urinary COPRO.
Lead poisoning
52
decreased iron in blood ----> __________ protoporphyrin
increased
53
most common cause of increased RBC porphyrins
Iron deficiency
54
What are the analytes in the disease of porphyrin metabolism
Porphobilinogen (PBG)
Urinary ALA
Fecal porphyrins
Urine porphyrins
Red cell porphyrins
Enzyme assays
Molecular genetics
55
Screening method of choice for PBG is __________.
Watson-Schwartz
56
____________ facilitates the movement of O2 from blood to muscle and serves
as a reserve O2 supply
Myoglobin
57
Consists of a single protein chain & one heme group
▪ Located in the muscle [skeletal & cardiac]
▪ Detection method: Immunoassay
Myoglobin
58
in general, Serum & Urine myoglobin: elevated due to...
Muscle damage
59
Historically, it was used to monitor Severe muscle tissue damage in crush injuries
and used to aid in diagnosis and monitoring of Muscle dystrophy
Myoglobin
60
is used to diagnose Acute MYOCARDIAL INFARCTIONS (MI)
Myoglobin
61
myoglobin is used to detect SUCCESSFUL _____________following tPA therapy in AMI
case
REPERFUSION
62
Can also be elevated in cases of open heart surgery, exhaustive exercise,
shock or severe renal failure
Myoglobin
63
It is small and filters readily into the urine.
▪ Urine will turn red-dark brown.
✦ Dipstick method
Myoglobin in urine
64
Free plasma Hb: __________ in intravascular hemolysis
increases
-Heart valve damage
- Complement fixation
Hb (α-chain) + Haptoglobbin
-Transported to the liver
-Cleared
65
Uncleared Free plasma Hb is oxidized to...
metHb
66
In IDA,
iron =
ferritin =
TIBC =
decreased
decreased
increased
67
myocardial infarction:
after ____ hours, myoglobin is no longer useful. (used only for acute!)
24
68
myocardial infarction:
What peaks at 16 hours and is back to normal in 2 days?
CK-MB
69
myocardial infarction:
What marker is widely used for chest pain? stays elevated for a week.
Troponin I
70
Uncleared Free plasma Hb is oxidized to _________.
metHb
71
"methemoglobinemia”
over ____% of total Hb
30
72
▪ At high concentrations, metHb results in...
hypoxia and cyanosis
73
Form of Hb in which Fe2+ ! Fe3+
▪Found in oxygenated or deoxygenated form
▪ It does NOT reversibly bind to the O2
Methemoglobin (metHb)
74
In normal individuals, ________________ will reduce Fe3+ to Fe2+
so that metHb is less than 1% of total Hb.
NADH metHb reductase*
1. NADH metHb reductase
2. Reverse NADPH metHb reductase
3. Antioxidant Vitamins: Ascorbic acid (Vit C)
4. **Glutathione (GSH)
75
Acquired _______ in normal individuals after exposure to agents such as
nitrites, nitrates, sulfonamides, aniline dyes and pyridium.
MetHb
*these oxides irons exceed the body's capacity to reduce iron
76
Individuals with hereditary HbM have persistent levels of metHb which can vary. What does this lead to?
1. Leading to the NADH metHb reductase deficiency 2. AA substitution in globin chain (heme pocket) Tyr ! His
77
Is there hemolytic anemia with acquired MetHb?
NO
78
How is MetHb assessed?
Spectrophotometry, HPLC, MS
MetHb is detected by reading absorbance at 630 nm.
79
SulfHb is the result of sulfur binding to hemoglobin. Is it reversible?
No
80
What can cause sulfhemoglobin?
Caused by exposure to sulfonamides or TNT in some individuals
Phenacetin, acetanilid (FDA prohibited painkiller)
81
SulfHb causes apoxia and cyanosis, but rarely causes __________ formation
Heinz body
82
CarboxyHb is the result of ______________ exposure.
carbon monoxide (CO)
83
Complex is greatly favored and binding is reversible, but very slow.
Usually caused by exposure to automobile exhaust, industrial pollutants, tobacco smoke, etc.
Hyperbolic treatment can displace CO from hemoglobin
CarboxyHb is the result of carbon monoxide (CO) exposure.
84
Primarily Functions of hemoglobin?
Transport O2 from lungs to tissues.
Acts as pH buffer
85
hemoglobin is a tetramer that can carry ___ oxygens.
4
86
what are the Four globin units?
2 α’s (α or ζ) and 2 β’s (ε, γ, β, or δ)
87
Hb composition for adults?
HbA(α2 β2), HbA2 (α2 δ2)
88
Fetal Hb composition?
HbF (α2γ2)
89
Each hemoglobin composition has its unique affinity for ____
O2
90
Embryonic hemoglobin composition?
Gower 1 (ζ2 ε2), Gower 2 (α2 ε2), Hb Portland (ζ2 γ2)
91
What are the buffers in the body?
-bicarbonate
-phosphorous
-hemoglobin
-albumin (minor but still important)
92
How many different hemoglobin defects are there?
over 700
93
Hemoglobin:
Defects in structure produce a group of diseases called...
Defect in rate of synthesis or amount of α or β-globin is called...
hemoglobinopathies
“thalassemia"
94
Structural abnormalities of hemoglobin are divided into what four groups?
1. AA substitutions
: common ones (e.g. HbM, HbS, HbC, HbD, HbE, HbO, HbG, etc)
2. AA deletion
(e.g. Hb GunHill)
3. Lack of protein chain termination signal or frame shift:
: Elongated globulin chains (e.g. Hb Constant Spring)
4. Fused or hybrid chains (Hb Lepore or Hb Kenya)
95
heptoglobin helps recycle...
iron
96
Sickle cell mutation. Intracellular crystals of deoxygenated
HbS form causing cells to adapt a sickle shape
what mutation causes this?
HbS (β6 glu --> val)
97
Sickle cell disease similar to HbS. Complications seem to be
less frequent than with HbS
what mutation causes this?
HbC (β6 glu ----> lys)
98
Second most common abnormality in the world. “Thalassemictype” expression of β causes microcytic cells & normochromic anemia.
what mutation causes this?
HbE (β26 glu ---> lys)
99
No anemia, but O2 affinity is higher than normal
what mutation causes this?
HbD (β121glu ----> gly)
100
Thalassemia of α-chains results in the tetramerization of __________________.
β chains
101
What is Hb (Bart’s)?
γ4 tetramerization
Diminished α-chains synthesis: excess γ chain synthesis****
102
What is HbH?
β4 tetramerization.
Diminished α-chain synthesis: excess β chain synthesis****
103
________ is glycosylated hemoglobin
Typically due to excess carbohydrates in patients.
Useful for monitoring DM patients.
HbA1c***
104
The elevation of GHb occurs about ___ wks after sustained elevation in blood glucose
3-4
105
What measures how well diabetes is being managed in the last month?
Hemoglobin A1c
106
Hemoglobin A1c:
* Good diabetic control: ___%
* Fair diabetic control : ____%
* Poor diabetic control : ____%
7, 10, 13-20
107
Hemoglobin A1c:
normal range for non DM....
pre DM range...
4-6
5.7-6.4
108
what are the Hemoglobin Methods?
Electrophoresis – KNOW THESE PATTERNS***
Molecular
Chemical
HPLC
Immunological
109
Electrophoresis:
Protein migration is from __________ to __________.
cathode (-) , anode (+)
110
In the Cellulose Acetate (pH 8.4), Hbs are _________ charged
negatively
111
In Citrate Agar (pH 6.0), some Hbs are ___________ charged
positively
112
What is the pH for Citrate Agar and Cellulose Acetate?
Citrate- pH 6
Cellulose Acetate- pH 8.4
113
Electrophoresis:
Where is it loaded for cellulose acetate?
Where is it loaded for citrate agar?
negative end
middle
114
What are the methods for hemoglobin?
-Molecular (DNA sequencing)
-Chemical
-HPLC (Column chromatography can be used to quantify A2 in β- thalassemias)
115
DNA sequencing is not useful for indicating....
severity of disease
116
Column chromatography can be used to quantify A2 in β- thalassemias.
A2 elutes from DEAE column first, elution of other Hb’s requires higher ionic strength
buffer.
Elutes measured at 415nm and A2 is expressed as % of total Hb.
HPLC
