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Biochemistry > Nitrogen Metabolism > Flashcards

Nitrogen Metabolism Flashcards

1
Q

AA production from the following enzyme activations:

  1. peptidase
  2. trypsin
  3. chymotrypsin
  4. elastase
A
  1. peptidase - Phe, Tyr, Glu, and Asp
  2. trypsin - Arg and Lys
  3. chymotrypsin - Phe, Tyr, Trp, and Leu
  4. elastase - Ala, Gly, and Ser
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2
Q

Hartnup Disease

A

Genetic metabolic disorder that affects the absorption of neutral amino acids (GAVLIMPFW)
Most of the symptoms are caused by lack of essential amino acids
No tryptophan to synthesize niacin (B3)

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3
Q

Cystinuria

A

Genetic metabolic disorder that affects the absorption of cysteine and basic amino acids (His, Lys, and Arg)
Only one essential amino acid-lysine (hard to see signs of deficiency)
High levels of cysteine in kidneys and bladder led to formation of kidney stones

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4
Q

Steps of Ubiquitin

A
  1. Protein is conjugated via a thioester bound to ubiquitin-activating enzyme (E1)
  2. Ubiquitin is transferred to a Cys sulfhydryl group on the ubiquitin-conjugating enzyme (E2)
  3. Ubiquitin-protein ligase (E3) transfers the activated ubiquitin to a Lys group on the target protein
  4. Ubiquitinylated proteins are degraded in the proteasomes
    * Must get rid of damaged proteins before they harm your body!
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5
Q

Marasmus

A

Child suffers from slowed growth and loss of muscle
Serum albumin levels are normal
Extremities are emaciated

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6
Q

Kwashiorkor

A 
Protein intake is low, but total calorie intake is near normal 
Hypoalbuminemia
Causes edema
Areas of hyperpigmentation 
Fatty liver
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7
Q

Cystic Fibrosis

A

can cause a blocked pancreatic duct resulting in decreased secretion of digestive enzymes
Treated with pancreatic enzymes
Concentrations of the enzymes need to be increased as the patient ages

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8
Q

Defected CPS1

A

low urine orotate, low blood citrulline and arginine, and high blood NH3

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9
Q

Defected OCT

A

high urine orotate (due to build up of carbamoyl phosphate), low blood citrulline and arginine, and high blood NH3

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10
Q

Defected Argininosuccinate Synthetase

A

extremely high citrulline (>1000 uM), low blood arginine and high blood NH3

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11
Q

Defected Argininosuccinate Lyase

A

moderately high citrulline (200uM), low blood arginine, and high blood NH3

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12
Q

Defected Arginase

A

high blood arginine and moderately high blood NH3

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13
Q

Essential Amino Acids

A

Arg, His Ile, Leu, Lys, Met, Phe, Thr, Trp, Val

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14
Q

Nonessential Amino Acids

A

Ala, Asn, Asp, Cys, Glu, Gln, Gly, Pro, Ser, Tyr

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15
Q

Pseudo- Essential

A

Cys and Tyr; considered non essential, but they are synthesized from an essential AA (Cys from Met and Tyr from Phe)

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16
Q

Pathways of AA Synthesis

  1. Pyruvate
  2. Oxaloacetate
  3. alpha-ketoglutarate
  4. 3PG/Glu
  5. Phe
A
  1. pyruvate makes Ala via PLP/B6
  2. oxaloacetate makes Asp via PLP/B6 which makes Asn
  3. alpha-ketoglutarate makes Glu via PLP/B6 which makes Pro, Asn, Asp, and Gln
  4. 3PG/Glu makes Ser which makes Gly and Cys via PLP/B6
  5. Phe makes Tyr via BH4
17
Q

Tetrahydrofolate

A

is a CH3 donor for several AA reactions and nucleotide metabolism; consumed via vitamin folate

18
Q

Ketogenic

A

Lys and Leu

19
Q

Both Ketogenic and Glucogenic

A

Ile, Phe, Thr, Tyr, Trp

20
Q

Glucogenic

A

Gly, Ala, Val, Met, Pro, Arg, His, Glu, Gln, Ser, Asn, Asp, and Cys

21
Q

Maple Syrup Urine Disease

A

Caused by a defect in enzymes that degrade branch chain amino acids (BCAA)
Branch chain amino acid build up in the blood and urine: Valine, Isoleucine, & Leucine
Makes urine smell like maple syrup (sweet smelling)
Several different classifications
Treated with a special diet low in BCAAs
BCAAs make up 25% of typical protein

22
Q

Phenylketonuria (PKU)

A

Caused by mutations to the gene that encodes for phenylalanine hydroxylase (PAH)
PAH catalyzes the reaction of phenylalanine to tyrosine
Mutation in PAH causes phenylalanine concentrations to be elevated- causing brain/mental defects
PKU can also be caused by defects in tetrahydrobiopterin (cofactor for PAH)
Treated with a diet low in phenyalanine

23
Q

Tyrosinemia I

A

Caused by defects in enzymes that break down tyrosine
Type 1- Fumarylacetoacetate hydrolase
Most severe form of the disease
Often presents as failure to thrive in infants
Leads to liver and kidney failure and problems with the nervous system
Diet must be controlled

24
Q

Tyrosinemia II

A

Caused by defects in enzymes that break down tyrosine
Type 2- Tyrosine aminotransferase
Affects eyes, skin and mental development
Diet must be controlled

25
Q

Alcaptonuria

A

Caused by a accumulation of homogentisic acid due to a defect in the enzyme homogentisate oxidase
Accumulation of homogentisic acid leads to cartilage damage in the spine and lower back pain
Arthritis
May also cause heart disease

26
Q

Purine Synthesis

A

R-5-P converted to IMP via 11 enzymes using 6 ATP
IMP makes AMP and GMP (reversible/salvaged)
IMP to AMP uses 2 enzymes and 1 GTP where Asp acts as N donor
IMP to GMP uses 2 enzymes and 1 ATP where Gln acts as N donor
build the base on top of PRPP

27
Q

Control of Purine Biosynthesis

  1. GMP to GTP (3 inhibitions)
  2. AMP to GTP (3 inhibitions)
  3. GTP and ATP (1 stimulation)
A

increased GTP (from GMP) stimulates AMP production
increased ATP (from AMP) stimulates GMP production
AMP to ATP and GMP to GTP inhibits PRPP synthase and GPA enzymes, which synthesize IMP
GMP inhibits its own side’s enzyme IMP dehydrogenase
AMP inhibits its own side’s enzyme adenylsuccinate synthetase

28
Q

Pyrimidine Synthesis

A

Gln to UMP using 6 enzymes and 2 ATP
UMP is converted to CTP and UTP
base formed first then add PRPP
dTTP isn’t converted to the ribonucleotide

29
Q

What makes up the Purine Rings? (C, N, and both)

A

C = HCO3-. Formate (2), and Glycine (2)
N = Aspartate amine, glutamate amide (2), glycine
Both: glycine

30
Q

Formation of dNTPs

A

not synthesized de novo
reaction catalyzed by ribonucleotide reductase
proper ratio is essential because otherwise can cause mutations (if too much or little of a dNTP)

31
Q

What makes up the Pyrimidine Rings? (C, N, and both)

A 
C = HCO3-
N = Aspartate and Glutamine
32
Q

Purine Degradation

A

Does not get back cost of energy, so more likely to be salvaged
If broken down = uric acid in urine
excess uric acid = gout
Pyrimidine degradation does not cause any problems
90% of cases = lack of excretion
Tx: allopurinol to inhibit xanthine oxidase

33
Q

Adenosine Deaminase Deficiency

A

enzyme for purine salvage
Causes severe problems in the immune system
The body isn’t able to produce T cells or B cells
Child must be placed in a sterile environment to survive
If HGPRT deficient = self mutilation/ mental defects

Biochemistry (2 decks)

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