Brainscape's Knowledge GenomeTM

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


See full index

Basic Biochemistry > 28. Heme Metabolism > Flashcards

28. Heme Metabolism Flashcards

1
Q

cyclic compound formed by linkage of 4 pyrrole rings through methyne bridges

A

porphyrins

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

heme containing enzymes

A

catalase
peroxidase
guanylate cyclase

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

Steps in heme synthesis

A
  1. formation of delta-aminolevulinic acid (ALA synthase)
  2. formation of porphobilinogen (ALA dehydrase)
  3. formation of linear tetrapyrrole (Porphobilinogen deaminase)
  4. formation of uroporphyrinogen III
  5. formation of protoporphyrinogen IX - occurs in the cytosol, transferred back to mitochondria
  6. protoporphyrinogen IX converted to protoporphyrin IX
  7. addition of iron to protoporphyrin IX by ferrochelatase –> Heme
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

rate limiting step of heme synthesis

enzyme and co-factor

A

formation of delta-aminolevulinic acid

•Glycine + Succinyl coa –> delta aminolevulinic acid

enz: ALA synthase
co-factor: pyridoxine

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

formation of porphobilinogen involves

A

condensation of 2 ALA by zinc-containing ALA dehydratase

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

formation of porphobilinogen is inhibited by

A

heavy metal ions e.g. lead that replace zinc

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

ferrochelatase is inhibited by

A

lead

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

introduction of iron into protoporphyrin IX occurs spontaneously, enhanced by

A

ferrochelatase

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

steps in heme degradation

A
  1. formation of bilirubin
  2. uptake of bilirubin by the liver
  3. formation of bilirubin diglucoronide
  4. secretion of bilirubin into bile
  5. formation of urobilins in the intestine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

formation of bilirubin

A

Heme –> biliberdin –> bilirubin

Enzyme: Heme oxygenase system

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

after 120 days , RBC are taken up and degraded by

A

reticulendothelial system (liver, spleen)

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

bilirubin is transported to the liver in the blood by binding to this protein

A

albumin

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

in the liver, bilirubin binds to this intracellular protein

A

ligandin

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

this enzyme is deficienct in
Crigler-Najjar I and II
Gilbert syndrome

A

Bilirubin glucuronyltransferase

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

this form of bilirubin is transported into bile canaliculi and then into the bile

A

bilirubin diglucuronide

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

in the intestine,

bilirubin –>

A

urobilinogen (colorless)

+ intestinal bacteria oxidize urobilinogen –> stercolin (brown)

17
Q

some urobilinogen is transported by the blood to

A
  • reabsorbed to the portal circulation

* kidne -> urobilin (yellow) -> excreted

18
Q

lead inactivates these enzymes in heme synthesis

A

ALA dehydratase

ferrochelatase

19
Q

clinical presentation of lead poisoning

A

•ÎÎ urinary ALA and free erythrocyte porphyrins
*microcytic, hypochromic anemia with basophilic stippling of RBCs
•headache, memory loss
•peripheral neuropathy, claw hand, wrist-drop
•nausea, abdominal pain, diarhea
•lead lines in gums
•lead deposits in epiphyses

20
Q

genetic or acquired disorders due to abnormalities in the pathway of biosynthesis of heme, which result in accumulation and ÎÎ excretion of porphyrins or porphyrin precursors

A

porphyrias

21
Q

most common porphyria

A

porphyria cutanea tarda

22
Q

clinical presentation of porphyria

A

photosensitivity
neuropsychiatric symptoms
abdominal pain

23
Q

results from elevated level of plasma bilirubin

A

jaundice

24
Q

the causes of jaundice can be distinguished as

A
  • prehepatic
  • hepatic
  • posthepatic
25
Q

used to measure bilirubin in serum

A

Van den Bergh reaction

26
Q

measures direct bilirubin

A

assay with no methanol

27
Q

measures total bilirubin

A

assay with methanol

28
Q

Heme synthesis takes place in the

A
  • cytosol and mitochondria of

* liver and bone marrow

29
Q

substrates of heme synthesis

A

succinyl A coa; glycine; Fe2+

30
Q

ALA synthase is inhibited by

A

high levels of hemin (heme derivative)

31
Q

substrates of heme degradation

A
  • Hme
  • NADPH
  • 2 UDP-glucuronic acid
32
Q

Product of heme synthesis

A
  • urobilinogen - excreted in urine
  • stercobilin- excreted inf feces
  • CO
  • Fe2+
33
Q

heme degradation begins

A

spleen - macrophages

34
Q

globin is recycled into

A

amino acids
•catabolized as intermediates of
–citric acid cycle
–fatty acid oxidation

35
Q
  1. Heme ring is opened by
A

oxidation; heme oxygenase

Heme –> Bilverdin (green pigment) + Fe3 + CO

36
Q
  1. formation of bilirubin
A

•second bridging methylene is reduced

Biliverdin –> bilirubin (red-orange) –> albumin –> liver
enz. biliverdin reductase

37
Q

in the liver, bilirubin is

A

conjugated with glucuronate by bilirubin glucuronyl transferase

38
Q

Free heme concentration greater than 1 micro M can be toxic because

A

it catalyzes the production of reactive oxygen species

39
Q

CO from heme degradation functions as

A

cellular messenger

vasodilator

Basic Biochemistry (50 decks)

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