Brainscape's Knowledge GenomeTM

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


See full index

Biochemistry MBBS > Amino Acids > Flashcards

Amino Acids Flashcards

1
Q

Both ketogenic and glucogenic amino acid

A
  1. Phenylalanine and tyrosine (tyrosine transaminase)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Tyrosine products

A
  1. Melanin (tyrosinase)
  2. Catecholamines (tyrosine hydrolase)
  3. Thyroxine (iodination)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Explain hydroxylation of phenyl alanine

A

Phenyl alanine hydroxylase

Tetra hydrobiopterin to dihydrobiopterin which is recycled by NADPH dependent dihydrobiopterin reductase

(tetrahydrobiopterin is formed from GTP by GTP Cyclo hydroxylase)

Irreversible reaction

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

Defects in phenylalanine hydroxylase reaction

A
  1. Defect in the enzyme is Phenyl ketonuria Type I (Classic)
  2. In dihydrobiopterin reductase , causes PKU type 2 and 3 (non classic)
  3. BH4 formation defect, PKU type 4 and 5 (non classic)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

Vitamin c requiring enzyme in tyrosine metabolism

A

PHPP hydroxylase
(dioxygenase)

Type 3 tyrosinemia

which converts PHPP ( pyruvate equivalent of tyrosine ) to homogentisate

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

Step in tyrosine metabolism requiring Fe2+

A

Homogentisate oxidase (dioxygenase)

Alkeptonuria

Converting homogentisate to maleyl acetoacetate (MAA)

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

GSH requiring enzyme in tyrosine metabolism

A

MAA cis trans isomerase

Which converts maleyl acetoacetate (MAA) to Fumaryl acetoacetate

(Which is later split by fumaryl acetoacetate hydrolase
Type 1 tyrosinemia)

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

Substances that activate the steps of tyrosine metabolism

A
  1. Vitamin C activates PHPP hydroxylase (Type 3 tyrosinemia)
  2. Fe+2 activates Homogentisate oxidase (Alkeptonuria)
  3. GSH activates MAA cis trans isomerase

Later fumaryl acetoacetate hydrolase acts
(Type 1 tyrosinemia)

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

Tyrosinemia type 1

A

Hereditary Tyrosinemia/hepatorenal tyrosinemia
Most common

FAA hydrolase

Resembles porphyria
Cabbage like odour

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

Treatment for hepatorenal tyrosinemia and alkeptonuria

A

Nitisinone NTBC

Inhibits PHPP hydroxylase

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

Type 2 tyrosinemia

A

Oculocutaneous / Richner Hanhart syndrome

Tyrosine transaminase
Corneal ulcer
Nonpruritic hyperkeratotic plaque seen in soles and palms

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

Type 3 tyrosinemia

A

Neonatal tyrosinemia

Least common

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

Hawkinsonuria

A

Mutant enzyme is PHPP hydroxylase (enzyme of type 3 tyrosinemia)

Swimming pool odour
Compound hawkinson produced

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

PKU

A

Phenyl alanine hydroxylase
Phenylacetate is responsible for mousy or musty odour
Hypopigmentation not albinism (blue eyes, blonde hair,fair skin)

Neurological manifestations(due to decreased thyroxine and neurotransmitter due to…)

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

Infants and PKU

A

Severe vomiting often misdiagnosed as congenital hypertrophic pyloric stenosis

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

Diagnosis of PKU

A
  1. Guthrie bacterial inhibition test using Bacillus subtilis
  2. Ferric chloride test (transient blue green colour) by phenyl pyruvate
  3. Blood phenylalanine level >20 mg/dl
  4. Tandem mass spectrometry /Fluorometric analysis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Treatment of PKU

A
  1. Restrict phenylalanine
  2. Sapropterin dihydrochloride /Kuvan (synthetic tetrahydrobiopterin)
  3. Large neutral amino acid (to prevent toxicity by phenylalanine saturation to tyrosine and tryptophan transport )
  4. Recombinant therapy using phenylalanine ammonia lyase
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Alkeptonuria ( part of Garrods tetrad (CAAP))

First inborn error to be detected

A

Benzoquinone acetate (reducing agent) is polymerised to alkeptonuria bodies in pinna ,sclera,…(blackish spots)

Ochronosis due to accumulation in cartilage

Low back ache in middle age

Blackish discloration in the top layers
Black or red in diaper

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

Lab diagnosis of alkeptonuria

A
  1. Alkalanisation of urine
  2. Ferric chloride test
  3. AgNO3 test
  4. X-ray of spine-
    parrot beak appearance
    Bamboo like spine
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

Segawa syndrome

A

GTP cyclohydrolase

Autosomal dominant ,in females

Dystonia with diurnal variation
BH4 level reduced
Phenylalanine level normal

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

Synthesis of DOPA

A
  1. Tyrosine hydroxylase (RDS)
  2. DOPA decarboxylase( with PLP)
  3. Dopamine beta oxidase
  4. N Methyl transferase (with SAM)
22
Q

The 3 aromatic amino acid hydroxylases requiring tetrahydrobiopterin, NADPH

A
  1. Phenylalanine hydroxylase
  2. Tyrosine hydroxylase
  3. Tryptophan hydroxylase

These are monooxygenases

23
Q

Degradation of catecholamines

A
  1. Dopamine- Homo Vanillic Acid
  2. Epinephrine - (COMT) metanephrine - (MAO) Vanillyl Mandelic acid
  3. Norepinephrine -(COMT) normetanephrine - (MAO) VMA

COMT - CatecholOMethyl transferase
MAO - Monoamine oxidase

24
Q

Triad of pheochromocytoma

A

Palpitation, headache, Profuse sweating

25
Q

Melanin

A

Tyrosine to DOPA then to Dopaquinone by tyrosinase

Then to melanin

26
Q

Albinism

A

Milky white skin and hair

Red eye reflex

27
Q

Sulphur test is answered by

A

Cysteine ,not methionine

Both are glucogenic

28
Q

Formation of SAM

A

Methionine adenosyl transferase (MAT)
This enzyme has 3 isoforms
MAT 1 and 3 are present in hepatic tissues
MAT 2 is present in the extra hepatic tissues

29
Q

Significance’s of SAM

A
  1. Transmethylation reactions
    a) creatine
    b) epinephrine
    c) metanephrine
    d) choline
    e) anserine
    f) melatonin
  2. Polyamines
  3. DNA methylation
30
Q

Polyamines formation

A
  1. Cadaverine (lysine on decarboxylation
  2. Putrescin (ornithine on decarboxylation via ornithine decarboxylase RDS)
  3. Spermidine (putrescin accepts amino group from decarboxylated SAM)
  4. Spermine ( spermidine accepts amino in the same way)
31
Q

Polyamine function

A

Positively charged so interact with DNA and regulate gene expression
Excreted in some cancers

32
Q

Formation of Homocysteine

A

From SAH (formed via methyl transferase) which is acted by adenosyl homocysteinase to get homocysteine

33
Q

Formation of methionine from homocysteine

A

N5 Methyl THFA is coupled with methyl B12

If there is vitamin deficiency of B12 , folic acid or PLP, it leads to homocystinuria, not homocysteinuria. Thus CVA, CAD increases.

34
Q

Transulfuration reactions

A

Homocysteine + serine = cystathionine (via cystathionine beta synthase and PLP)
= homoserine + cysteine (via cystathionase and PLP)

35
Q

Fate of homoserine

A

Converted to propionyl CoA then to succinyl CoA then via TCA to glucogenic

36
Q

Oast House syndrome

/ Smith Strang disease

A

Defect in methionine transporter which transports methionine from intestine to blood

37
Q

Primary hyper methioninemia

A

Deficiency of MAT

Smell of boiled cabbage

38
Q

Classic homocystinuria (no E)

A

Deficiency of cystathionine beta synthase

39
Q

Cystathioninuria

A

Defect of cystathionase

Cyanide nitroprusside test -ve

40
Q

Non classic homocystinuria (no E)

Causes

A

Deficiency in N5 THFA (from folic acid) or methyl B12
1. N5 THFA deficiency may occur due to defect in MTHFR (Methylene THF reductase)
Megaloblastic anaemia absent
2. B12 deficiency
Megaloblastic anaemia present

41
Q

Classic homocystinuria

Clinical features

A
  1. Developmental delay
  2. Around 3 years, decreased vision, progressive myopia and quivering of eye (iridodonesis)
    Medial and downward dislocation of lens (ectopia lentis)
  3. Skeletal deformities
  4. Severe mental retardation
  5. Thromboembolism

Resembles Marfans syndrome

42
Q

Skeletal deformities of classic homocystinuria

A
  1. Pectus cavinatum or pectus excavatum
  2. Arachnodactyly
  3. Knee deformities
    Genu valgum/ varum
  4. Coxa vara
    Pescavus
  5. High arched palate
43
Q

Diagnosis and screening of homocystinuria

A

Diagnosis by Cyanide nitroprusside test (magenta colour) ,answered by homocysteine, homocystine, cysteine and cystine.

Screened by tandem mass spectrometry

44
Q

Treatment of classic homocystinuria

A
  1. High doses of vitamin B6
45
Q

Non classic homocystinuria

A

Homocysteinemia

Methionine level is decreased but cysteine level is normal

46
Q

Cystinuria

A

Part of Garrods tetrad (CAAP)
Defect in diabetic amino acid transporter in intestine and renal tubules

COLA in urine
Cystine (no E) ,ornithine, lysine, arginine

Cyanide nitroprusside test +ve

47
Q

Cystinosis

A

Lysosomal storage disorder
H+ driven cystine transporter called cystinosin (of gene CTNS)
Hepatic failure, renal failure, corneal opacity, bone marrow also affected

48
Q

Treatment of cystinosis

A

Cysteamine which converts cystine to cysteine

49
Q

Cysteine functions

A
  1. On decarboxylation gives betamercapto ethanolamine
  2. CoA
  3. Taurine (bile acids)
  4. Glutathione
  5. Cystine
50
Q

Glutathione

A

Tripeptide (gamma glutamyl cysteinyl glycine)

Pseudopeptide (not an alpha carboxyl bond)

51
Q

Functions of glutathione

A
  1. Meister cycle (for amino acid transport)
  2. RBC membrane integrity
  3. Maintains Fe as +2
  4. Phase 2 xenobiotic reactions- conjugating agent
  5. Antioxidant
  6. Coenzyme of cis trans isomerase MAA to FAA
52
Q

Enzymes involved in RBC membrane integrity

A

Glutathione peroxidase containing selenocysteine (which converts H2O2 to H2O by formation of GSSG)

GSSG is recycled back to GSH by glutathione reductase (containing riboflavin) and NADPH

Biochemistry MBBS (10 decks)

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