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GI > Nitrogen Elimination and Carbon Chain Metabolism II > Flashcards

Nitrogen Elimination and Carbon Chain Metabolism II Flashcards

1
Q

The initial step in urea synthesis occurs in the mitochondria, and requires 2 ATP’s per urea. Note that the ATP is hydrolyzed in two distinct steps that generate

A

Pyrophosphate and then inorganic phosphate

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2
Q

The α-NH3 from most amino acids is transferred to α-ketoglutarate. The sole purpose of this mechanism is to concentrate all the α-NH3 groups, from different amino acids, predominantly into

A

Glutamate

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3
Q

Although this does not reduce the overall levels of nitrogen, it permits a single enzyme, glutamate dehydrogenase, to release nitrogen from glutamate and initiate the formation and excretion of

A

Urea

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4
Q

Non-specific proteases, such as those expressed in the gut can be extremely deleterious to other

A

Cellular proteins

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5
Q

Glutaminase, Asparaginase and glutamate dehydrogenase release ammonia from

A

Glutamine, asparagine, and glutamate respectively

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6
Q

Reduced expression of N-acetylglutamate could result in

A

Ammonia toxicity

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7
Q

Reduced expression of N-acetylglutamate could result in ammonia toxicity. This defect could be severe in individuals with liver disease. This toxicity could be exacerbated by a

A

High protein diet

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8
Q

Amino acids are classified as being either

A

Glucogeninc or ketogenic

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9
Q

Channeled into pyruvate or other TCA intermediates, and can be fully catabolized, or can be used for the formation of glycogen

A

Glucogenic amino acids

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10
Q

Terminate as acetyl-CoA or its derivatives, and the energy yield is lower

A

Ketogenic amino acids

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11
Q

Glucogenic amino acids can also produce acetyl-CoA, although the important distinction is that the ketogenic amino acids do not enter

A

TCA

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12
Q

The synthesis of cysteine requires

A

Methionine

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13
Q

The production of tyrosine requires

A

Phenylalanine

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14
Q

A high-energy and unstable compound, containing a CH3 group that is linked to a sulfur atom in methionine

A

SAM

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15
Q

The methyl group in SAM is transferred rapidly to

A

DNA, RNA, and hormones

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16
Q

After the methyl group has been contributed to a reaction, the resulting S-adenosyl-homocysteine can be converted back to

A

Methionine

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17
Q

This reaction requires the co-factor methylcobalamin and

A

Methyltetrahydrofolate

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18
Q

Derived from vitamin B12

A

Methylcobalamine

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19
Q

Homocysteine can also be converted to cysteine, in a reaction that requires

A

Pyridoxal phosphate/vitamin B6

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20
Q

An essential vitamin that performs in single carbon donor reactions

A

Folate

21
Q

Can receive carbon from a variety of different donor molecules, and based on the chemical form, distinct bonds are formed with its nitrogen atoms

A

Tetrahydrofolate

22
Q

Carbonic acid is the hydrated form of CO2, and is transported by

A

Biotin

23
Q

You should recognize that a defect in enzymes that form either carbamoyl phosphate (ie: carbamoyl phosphate synthase I), or stimulate its activity by N-acetylglutamate (N-acetylglutamate synthase) could have

A

Similar negative effects

24
Q

Carbamoyl phosphate synthase I defects / N-acetylglutamate synthase defects result in the accumulation of

A

Ammonia

25
Q

Given the extreme toxicity caused by ammonia to the CNS, defects in these pathways can cause severe cognitive deficiencies

A

Carbamoyl phosphate synthase I defects / N-acetylglutamate synthase defects

26
Q

Can breach the permeability across the hepatocyte cell membrane, and release transaminases into circulation

A

Liver disease

27
Q

A common genetic defect (1/15,000 incidence) that causes accumulation of phenylalanine, and reduces the synthesis of tyrosine

A

Phenylketonuria (PKU)

28
Q

Although there are multiple causes for PKU, the classic form results from a defect in the enzyme

A

Phenylalanine hydroxylase (PAH)

29
Q

Functions to convert phenylalanine to tyrosine

A

PAH

30
Q

Failure to convert phenylalanine to tyrosine results in the accumulation of phenylalanine and other byproducts, and is accompanied by progressive

A

Mental retardation

31
Q

Phenylalanine hydroxylase requires a cofactor called

-Defects in the synthesis of this cofactor can also cause PKU

A

Tetrahydrobiopterin

32
Q

Large neutral amino acid transporters are required for transport of phenylalanine and certain other amino acids across the

A

Blood-brain barrier

33
Q

However, high levels of phenylalanine can competitively block the entry of other neutral amino acids into the

A

Brain

34
Q

Required for the synthesis of the pigment melanin

A

Tyrosine

35
Q

PKU patients tend to be faired and frequently have

A

Greener eyes

36
Q

Specific amino acid transporters in the kidney can reabsorb amino acids in the urine. However, defects in specific transporters can lead to high levels of certain amino acids in the blood

A

Blue-diaper syndrome

37
Q

For instance, accumulation of tryptophan, as a result of an absorption defect in the intestine, results in its degradation by intestinal bacteria, and the generation of

A

Indole

38
Q

Following oxidation indole is converted to indigo blue, which is excreted in the urine, and stains the diaper

A

Blue

39
Q

This is a rare, autosomal recessive trait that is accompanied by digestive problems and visual impairment

A

Blue-diaper syndrome

40
Q

A rare disease that is caused by the failure to remove the α-amino group from tyrosine

A

Aminotransferase defect. Type II tyrosinemia

41
Q

Aminotransferase defect. Type II tyrosinemia is a rare disease that is caused by the failure to remove the α-amino group from tyrosine. The defect lies in the gene encoding

A

Tyrosine aminotransferase

42
Q

Aminotransferase defect. Type II tyrosinemia causes accumulation of tyrosine, and is associated with

A

Mental retaration and defects in the eyes and skin

43
Q

One of the most frequently occurring genetic defects (~1/10,000)

A

Polycystic Kidney Disease (PKD)

44
Q

Incurable, and is associated with the formation of fluid filled cysts in both kidneys

A

Polycystic Kidney Disease (PKD)

45
Q

Polycystic Kidney Disease (PKD) is also associated with an

A

Auto immune effect

46
Q

Adult symptoms of PKD include

A

Fatigue, headaches, UTI, and hypertension

47
Q

Individuals with advanced disease have a high incidence of

A

Kidney stones and liver damage

48
Q

The final phase, that leads to death, is caused by

-results from complete renal failure

A

Uremia

49
Q

Treatment for PKD might include reducing blood pressure (antihypertensive meds / diuretics / low salt diet), close monitoring for infection caused by hernia, antibiotic therapy to suppress inflammation and infusion of

A

RBC

GI (59 decks)

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