Brainscape's Knowledge GenomeTM

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


See full index

Biochemistry Block 3 > Heme Metabolism > Flashcards

Heme Metabolism Flashcards

1
Q

What is the difference between heme and hemin

A 
Heme = Fe2+
Hemin= Fe3+
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Two main places where heme synthesis occurs?

However, heme synthesis happens in all cells EXCEPT

Site within the cell of heme synthesis?

A

Liver and bone marrow

RBCs

Mitochondria and cytoplasm

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

What assists in heme synthesis in the liver

A

Cytochrome p450

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

For our purposes, which 2 steps happen in the mitochondria?

A

1st step and last 3 steps; rest occur in cytoplasm

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

Two things required for heme biosynthesis

A

Glycine and succinyl CoA (these are the beginning substrates for first step)

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

First step of heme synthesis?

By which enzyme?

A

Glycine and succinyl CoA decarboxylate to form ALA by ALA synthase

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

First step of heme synthesis requires?

A

Vitamin B6 (pyridoxal phosphate)

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

What is the rate limiting enzyme in heme synthesis

What inhibits this enzyme?

A

ALA synthase

Heme/hemin

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

What happens in step 2 of heme synthesis

What does this enzyme require?

What is significant about the enzyme in this step

A

2 molecules of ALA condense to form porphobilinogen by ALA dehydratase

Requires zinc

It is inhibited by heavy metals (lead)

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

Lead poisoning will lead to what two things?

A

Anemia and elevation of ALA and zinc protoporphyrin

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

Besides ALA dehydratase, what other enzyme is inhibited by lead?

A

Ferrochelatase

~so these 2 enzymes are the cause of anemia in lead poisoning

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

Deficiency in any of the other enzymes of heme synthesis that have not been mentioned cause what?

A

A condition known as porphyria

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

Name the following enzyme used for the last 3 steps of heme synthesis:

  1. Coproporphyrinogen III -> protoporphyrinogen IX
  2. Protoporphyrinogen IX -> protoporphryrin IX
  3. Protoporphyrin IX -> heme
A
  1. Coproporphyrinogen III oxidase
  2. Protoporphyrinogen oxidase
  3. Ferrochelastase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q
  1. Disorders in any of the beginning steps of heme synthesis will have what kind of symptoms?
  2. Disorders in the ending steps?
A
  1. Either GI or neuro/psych

2. Either photosensitive or skin

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

Porphyrias:

  1. Caused due to a defect in?
  2. Reduced heme formation will lead to increase function of which enzyme?
  3. Cells of which two organs will be most affected by these disorders
A
  1. Heme sythesis
  2. ALA synthase
  3. Bone marrow (erythropoietic) and liver (hepatic)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Erythropoietic porphyria:
1. Characterized by

  1. Complications
A
  1. Skin rashes and blisters that appear early in childhood

2. Liver cirrhosis/progressive hepatic failure

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

Two subsections for hepatic porphyrias

A

Acute and chronic

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

Acute (intermittent) porphyria:

  1. 2 other types
  2. Symptoms
A
  1. Hereditary coproporphyria, variegate porphyria

2. Acute attacks of GI, neuro/psych, and cardiovascular symptoms

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

Chronic porphyrias:

  1. 2 types
  2. Symptoms
A
  1. Porphyria cutanea tarda and hepatoerythropoetic (rare)

2. Sensitivity to sunlight and blisters on the skin

20
Q

Acute intermittent porphyria:

  1. Deficiency in what enzyme? (Give both names for the enzyme)
  2. Leads to accumulation of
  3. Symptoms
  4. What can cause an acute attack
A
  1. PBG deaminase / HMB synthase
  2. ALA and PBG
  3. Abdominal pain and neuro/pysch
  4. Barbiturates and ethanol (induction of cytochrome p450)
21
Q

Porphyria cutanea tarda:

  1. Deficiency in what enzyme
  2. Chronic disease of __ and __
  3. Onset?
  4. Clinical expression is influenced by?
  5. Leads to accumulation of
  6. Clinical symptoms?
A
  1. Uroporphyrinogen decarboxylase
  2. Liver and erythroid tissue
  3. Late; 40s-50s
  4. Iron overload, exposure to sun, and infection
  5. Porphyrins
  6. Skin / urine will turn from red to brown; “werewolf” appearance
22
Q

What two things can repress ALA synthase?

A

High carbs and administration of hemin

23
Q

Patients with photosensitivity may benefit from?

A

Beta carotene (lessen production of free radicals)

24
Q

Catabolism of heme occurs in what type of cells? In what two organs, mainly?

~85% get degraded this way, how do the other 15% get degraded?

A

Reticuloendothelial cells; liver and spleen mainly

From turnover of immature RBCs and cytochromes from extraerythroid tissues

25
Q

Two parts of heme?

What is globin composed of?

Which of the above answers can be reused?

A

Porphyrin and iron

Amino acids

Iron and amino acids can be reused; porphyrin cannot

26
Q

Name 3 functions of carbon monoxide (CO)

A

Anti-inflammatory, signaling molecule, and vasodilator

27
Q

What is indirect/unconjugated bilirubin

A

Orange/yellowish bilirubin that is formed in extra-hepatic tissues

28
Q

Main difference between conjugated and unconjugated bilirubin

A

Conjugated is soluble in water so can be secreted in the urine/blood

29
Q

Tissues in the reticuloendothelial system that these extra-hepatic processes can happen in

A

Spleen, macrophage, lymph tissue

30
Q

Formation of indirect bilirubin requires what two things?

What does formation of indirect bilirubin produce?

A

NADPH and oxygen

Biliverdin, CO, iron, and NADP+

31
Q

Next step is converting biliverdin to bilirubin - what enzyme does this?

A

Biliverdin reductase

32
Q

Bruises change color based on biliverdin/bilirubin - what are the colors of each

A

Biliverdin- green

Bilirubin - yellow/orange

33
Q

If indirect bilirubin is formed outside of the liver, what does it require in order to get into the liver?

A

Facilitated transport via albumin

34
Q

What are the two sites that albumin has for bilirubin?

A

High affinity and low affinity sites

35
Q

What happens once indirect bilirubin enters the liver?

A

It gets converted to direct/conjugated bilirubin (bilirubin diglucuronide) by bilirubin glucuronyl-transferase which uses 2 UDP-glucuronic acid

36
Q

How does conjugated bilirubin leave the liver and go into bile?

What is significant about this

A

Active transport - requires energy

Rate limiting for the entire process of hepatic bilirubin metabolism

37
Q

Bilirubin glucuronyltransferase can be induced by ?

A

Phenobarbital

38
Q

3 inherited unconjugated hyperbilirubinemias?

All 3 of these disorders have to do with a deficiency in which enzyme

A

Crigler-Najjar 1, Crigler-Najjar 2, and Gilberts syndrome

UDP glucuronyl transferase deficiency

39
Q

Main difference between the 3 disorders

A

CN1 is complete deficiency of enzyme-poor survival
CN2 is partial deficiency- medium severity
Gilberts is minimal deficiency- not clinically significant

40
Q

2 inherited conjugated hyperbilirubinemia disorders?

Both occur when there is a defect in?

A

Dubin Johnson syndrome (major effect) and Rotors syndrome (minor effect)

Excretion of bilirubin into the bile

41
Q

Symptoms of dubin johnson?

Symptoms of rotors?

A

Black pigmented liver

Liver-no pigmentation

42
Q

In the intestine, what happens to bilirubin

A

It goes back to unconjugated bilirubin and then converted to urobilinogen which is reabsorbed/reexcreted to the liver and excreted in urine

43
Q

Small percentage of bilirubin does not convert to urobilinogen, instead it oxidizes to?

A

Stercobilin (excreted in feces - responsible for brown color)

44
Q

Identify if the following is describing conjugated or unconjugated bilirubin:

  1. Soluble in methanol
  2. Absent in urine
  3. Excreted in bile
A
  1. Unconjugated (conjugated is soluble in water/blood)
  2. Unconjugated
  3. Conjugated
45
Q

Total bilirubin= 1.0 mg/dl
Conjugated bilirubin=?
Unconjugated bilirubin=?

A

Conjugated= 0-0.2 mg/dl

Unconjugated=0.2-0.6 mg/dl

46
Q

What is hyperbilirubinemia?

What sign/symptom can it result in

A

When bilirubin in blood exceeds 1 mg/dl

Jaundice (when serum bilirubin >2 mg/dl

47
Q

Jaundice:

  1. Yellowing of what areas of the body?
  2. How do you measure this?
  3. What causes the yellowing?
A
  1. Skin, nail beds, and sclera
  2. Van den Bergh reaction
  3. Deposition of bilirubin

Biochemistry Block 3 (11 decks)

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