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Flashcards in Heme Synthesis & Hemoglobin Deck (49)
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1

What are the 3 main functions of heme?

transport of O2
electron transport
oxidation-reduction reactions (cyps)

2

Where is heme produced?

bone marrow-hemoglobin
liver-cyps
all other cells EXCEPT mature erythrocytes

3

What is a porphyrin?

cyclic tetrapyrroles capable of chelating to various metals to form essential prosthetitic groups for various biological molecules

4

What is heme?

Ferroprotoporphyrin IX

5

Does heme contain Fe3+ or Fe2+?

Fe2+

6

Where is ALAS localized to?

inner mitochondiral membrane

7

What is ALAS dependent on as a cofactor?

PLP (pyridoxal phosphate)

8

What are the 2 isoforms of ALAS? Location?

1-liver
2-erythroid/reticulocyte

9

Which isoform of ALAS undergoes feedback inhibition?

ALAS1-feedback inhibition by heme (at translational and transcriptional levels & mitochondrial import)
ALAS2-NOT regulated by feedback inhibition

10

How can lead poisoning affect the ALAD reaction?

Pb2+ can displace Zn2+ and eliminate catalytic activity, this leads to increased ALA in urine

11

What does lead poisoning mimic?

Acute porphyrias

12

What affects does ALA have on the brain?

it is toxic, causes the neurological effects of lead poisoning, Pb2+ may also directly affect nervous system

13

What does UROS do?

step 3 pt 2
converts uroporphyinogen III to the right isomer

14

What does ALAS do?

step 1
condenses glycine and succinyl Co-A to yield ALA

15

What does ALAD do?

step 2
condenses 2 molecules of ALA to form one molecule of PBG

16

What does PBGD do?

step 3 pt 1
form a linear tetrapyrrole

17

What does UROD do?

step 4
decarboxylates acetate side chains to methyl group

18

What does CPO do?

step 5
converts propionic acid side chains to vinyl groups

19

What does PPO do?

step 6
converts rpotoporphyrinogen IX to protoporphyrin IX

20

What does ferrochelatase do?

enhance the rate of Fe2+ into protoporphyrin IX insertion

21

What can inhibit ferrochelatase?

lead (increase protoporphyrin in urine)
iron deficiency

22

What is porphyria?

defect in heme biosynthesis
inherited or acquired

23

Inheritance of porphyria?

Al are AD except congential erythropoietic prophyria (AR)

24

What is the most common porphyria?

Porphyria cutanea tarda (PCT)

25

Most common acute porphyria?

Acute Intermittant Porphyria (AIP)

26

Most common erythropoietic porphyria?

Erythropoietic protoporphyria (EEP)
most common porphyria in childhood

27

What are symptoms of porphyrias with early defects?

accumulation of ALA, neurologic dysfunction

28

What are symptoms of porphyras with late defects?

sunlight induced cutaneous lesions, due to accumulation of cyclic tetrapyrroles, generare ROS

29

Acute porphyria symptoms? causes?

periodic acute attacks
abdominal pain, neuro defects, psych, red urine
casuses: drugs, environment, diet

30

chronic porphyria symptoms?

dermatologic disease that may or may not include liver and nervous system