Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Heme/Lymph Exam I > Heme, Iron , Bilirubin > Flashcards

Heme, Iron , Bilirubin Flashcards

1
Q

where does hemoglobin synthesis occur

A

red blood cells in the bone marrow

**normal synthesis depends on adequate supply of Fe, normal heme, and normal globin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what form of Fe can hemoglobin bind

A

Fe2+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

methemoglobin reductase

A

converts methemoglobin (Fe3+) back to hemoglobin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

once inside the cell, what happens to heme

A

heme oxgenase oxidizes the fe2+ in heme and then releases Fe3+ which is then reduced to Fe2+

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

where does Fe2+ that is inside a duodenal epithelial cell go

A

binds to mobilferrin for transit across the cell to the basolateral membrane

Fe2+ then leaves the cell via ferroportin (FP1) and after hephaestin oxidizes it to Fe3+ the iron binds to transferrin in plasma

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

where is heme iron from ?

A

from breakdown of myoglobin and hemoglobin in meats

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

where is nonheme primarily from

A

vegetables

may be either ferrous or ferric form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what happens to dietary Fe3+ from nonheme iron prior to entering duodenum

A

reduced to Fe2+ by ferric reductase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

DMT1

A

cotransports Fe2+ and H into cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

apoferritin

A

binds to iron to form ferritin the storage form of iron

decreased apoferritin synthesis (usually due to liver disease) results in elevated serum iron levels

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

hepcidin

A

negative regulator of iron absorption

secreted by hepatocytes

binds to ferroportin at the cell surface to initiate ferroportin internalization and degradation

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

loss of hepcidin protein

A

results in severe iron overload- hemochromatosis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

increased hepatic hepcidin production (associated with inflammatory conditions)

A

may lead to anemia of chronic disease by blocking iron absorption

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is bilirubin

A

breakdown product of hemoglobin molecule liberated from dead erythrocytes by the reticuloendothelial system

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what are the major steps in bilirubin metabolism

A

o Hemoglobin from RBCs is degraded into heme-iron (Fe) complex + a globin chain by macrophages
o Heme moiety is converted to biliverdin + Fe
o Fe is reabsorbed and recycled to be used in formation of new RBCs
o Biliverdin is converted to UNCONJUGATED OR WATER-INSOLUBLE bilirubin (≈ 250-350 mg/day)
o Unconjugated bilirubin can be converted from the “trans” to the “cis” form by light. The cis form is more easily excreted in urine.

o Unconjugated bilirubin enters portal circulation where it is combined with albumin
o It then enters the hepatocytes through the sinusoids via two mechanisms:
• Passive diffusion
• Receptor-mediated endocytosis
o The unconjugated bilirubin travels to the smooth endoplasmic reticulum (SER) of the hepatocyte
o At the SER, the unconjugated bilirubin undergoes a conversion to CONJUGATED OR WATER-SOLUBLE bilirubin catalyzed by the enzyme uridine 5’-diphosphate glucuronyl transferase (UDPGT).

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

UDPGT

A

adds glucuronide to the bilirubin molecule (primarily two glucuronide molecules) to form bilirubin diglucuronide which is the conjugated or water-soluble form of bililrubin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

what happens to conjugated bilirubin once it has now been made water soluble

A

o The conjugated bilirubin is then delivered to the opposite side of the hepatocyte and enters the bile canaliculi for active secretion into…
o The intestinal tract where intestinal bacteria degrade it to urobilinogen and urobilin
o A small part of the urobilinogen remaining in the gut is metabolized to stercobilin, which is the compound giving stool its pigment
o However, the majority of the urobilinogen is reabsorbed by the gut and re-excreted by the liver with a small amount being excreted in the urine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

when is urinary urobilinogen elevated

A

hyperbilirubinemia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

increased urinary bilirubin occurs when ….

A

there is an increase in serum conjugated bilirubin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what is the normal range of total serum bili

A

0.2-1.0

of this total usually less than 0.2 is conjugated

the remainder is unconjugated

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

when does jaundice appear

A

when bili exceeds 2-3 mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what levels of bili cause kernicterus

A

bili exceeding 15-20 mg/dL

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what are the causes of prehepatic jaundice

A

hemolytic process

the liver is usually functioning normal

excessive bilirubin presented to the liver for metabolism

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what are the lab findings in prehepatic jaundice

A

increased serum unconjugated bili (total bili usually doesn’t exceed 5 mg)

negative urine bilirubin

urinary urobilinogen increased

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

what are some causes of hepatic jaundice

A

Gilbert’s-
Crigler-Najjar
Dubin Johnson
Hepatitis

26
Q

Gilbert’s

A

enzyme mutation/impaired hepatocellular uptake

serum total bili <3.0 = primarily composed of unconjugated bili

increased urinary urobilinogen

27
Q

Crigler-Najjar type I

A

enzyme mutation/defective conjugation

serum unconjugated bili >5.0

increased urinary urobilinogen

28
Q

Dubin-Johnson

A

defective secretion by hepatocyte

increased serum conjugated bili

29
Q

hepatitis with lower conjugation or excretion

A

increased serum direct and indirect bili with total levels of 5-10 mg/dL

30
Q

what are the causes of posthepatic jaundice

A

impaired excretion of bilirubin

mechanical obstruction of the flow of bile into the intestine due to gallstones or tumors

31
Q

what are the lab findings of posthepatic jaundice

A

increased serum AND urine conjugated bilirubin

decreased level of urobilin/stercobilin in stool (Clay colored stools***)

negative urinary urobilinogen

32
Q

when does HbF disappear from the RBC’s of normal infants

A

by age of 6 months

33
Q

what is Hb gower

A

embryonic form of Hb

34
Q

how is heme formed

A

1) condensation of succinyl-CoA and glycine for form ALA (aminolevulinic acid) by ALA synthase (comitted step, rate-limiting)
2) PBG synthase (AKA ALA dehydratase) (porphobilinogen synthase) catalyzes the condensation of two molecules of ALA to form PBG (porphobilinogen) in the cytosol
3) Condensation of 4 molecules of PBG to form protoporphyrin ring -
4) iron is inserted into protoporphyrin by ferrochelatase to form heme

35
Q

ALA synthase

A

in the mitochondria

succinyl CoA + glycine to form ALA

mutations in this cause sideroblastic anemia

36
Q

PBG synthase

A

(Aka ALA dehydratase) catalyzes the condensation of two molecules of ALA to form PBG (happens in the cytosol)

mutations in this enzyme would result in porphyria

Pb poisoning ?

37
Q

ferrochelatase

A

incorporation of ferrous iron into protoporphyrin (in the mitochondria)

Pb poisoning

Mutation= protoporphyria

38
Q

where does globin synthesis occur

A

cytoplasm of normoblasts and reticulocytes (immature erythrocytes) - synthesized in the cytoplasmic ribosomes

increased availability of heme promotes globin synthesis

39
Q

alpha globin chains made on what chromosome

A

16

40
Q

beta globin chains are made on what chromosome

A

11

41
Q

HbF, Hb Portland

A

most abundant Hb in fetal development

42
Q

adult Hb

A

HbA

43
Q

is there any HbF in adults?

A

yes a very small amount

44
Q

what takes over function of break down of red cells if the pt has no spleen

A

liver

45
Q

what are the 2 inefficient pathways in red cells that are the energy sources

A

Glycolysis

pentose phosphate cycle (PPC) –> supplies NADPH to maintain reduced state of glutathione and sulfhydryl groups

46
Q

after removal of senescent red cells from the circulation Hb is degraded within macrophages of the RES into its 3 components:

A

Fe: goes into storage for reutilization (recycling)

Protoporphyrin: split and converted to bilirubin, excreted from body

Globin: degraded and returned to amino acid pool for possible reutilization

47
Q

how is the porphyrin ring broken down

A

heme oxygenase

yields CO (which forms carboxyhemoglobin) and biliverdin

Biliverdin is reduced to bilirubin in the macrophage and transported to the liver attached to plasma albumin.

It is removed from the circulation by the hepatocytes and conjugated for excretion in bile

48
Q

deoxyhemoglobin

A

reduced hemoglobin

49
Q

oxyhemoglobin

A

hemoglobin carring oxygen

50
Q

methemoglobin

A

(usually <3% of total hgb) hemoglobin carrying oxidized (ferric) iron…
loses its ability to carry oxygen & becomes
non-functional

51
Q

methemoglobin reductase

A

converts methemoglobin back to hemoglobin

If Fe2+ is oxidized to Fe3+, (can be due to oxidizing drugs such as nitrites or sulfonamides), methemoglobin is formed
and is incapable of binding oxygen.

52
Q

Sulfhemoglobin

A

(Usually not present) oxidized, partially denatured hemoglobin which may result in RBC destruction & hemolysis. Usually due to sulfur-containing drugs (sulfonamides) or aromatic amine drugs (phenacetin, etc.)
Cannot carry O2
Phenacetin- pain relieving and fever-reducing drug, widely used from its introduction in 1887 until banned in the US by the FDA in 1983

53
Q

Carboxyhemoglobin

A

(Usually <3% of total hemoglobin) hemoglobin carrying CO produced during heme degradation to bilirubin. CO is eliminated via respiration Can also be formed due to CO poisoning

54
Q

HbF

A

2α & 2γ globin chains

55
Q

HbA

A

2α & 2β globin chains

56
Q

HbA2

A

2α & 2δ globin chains

57
Q

when does the gower Hb go away

A

around 3 months

58
Q

when does beta chain of Hb start to form

A

3 months

59
Q

when does fetal hemoglobin start to form

A

3 months

60
Q

what occurs in Sickle cell disease (S/S)

A

Missense mutation of β globin chain: amino acid substitution at position 6- valine for glutamic acid

HbA –> HbS

develops around 6 months

HbS replaces HbF

Heme/Lymph Exam I (4 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions