Biochemistry - Metabolism - Proteins and stuff Flashcards

1
Q

Which amino acids are “essential” amino acids?

A

Glucogenic: Methionine, Valine, Histidine
Glucogenic/ketogenic: Isoleucine, Phenylalanine, Threonine, Tryptophan
Ketogenic: Leucine, Lysine

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

Which amino acids are acidic?

A

Aspartic acid, Glutamic acid. (Neg at body pH).

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

Which amino acids are basic?

A

Arginine, Lysine, Histidine.

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

Which amino acids are required during periods of growth?

A

Arg and His

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

Which amino acids are in histones?

A

Arg and Lys.

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

What is the purpose of the urea cycle?

A

In order for the carbon skeletons of amino acids to be broken down and used as energy the nitrogen must be removed; the urea cycle converts nitrogen into urea so it can be excreted.

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

What is the basic structure of an amino acid?

A

H2N-CH-COOH with an R group coming off the middle C. The R group distinguishes the amino acid.

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

What is the structure of carbamoyl phosphate?

A

CO2 + NH3 –(ATP)–> H2N-COO-phosphate

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

What is required for the conversion of CO2 + NH3 to carbamoyl phosphate?

A

N-acetylglumatate, 2ATP + carbamoyl phosphate synthetase

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

What is the structure of urea?

A

H2N-CO-NH2

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

What is the role of alanine/glutamate in taking nitrogen from amino acid to urea?

A

In Muscle: Amino acid (NH3) —> glutamate (NH3) –> Alanine (NH3). Alanine can be transported to Liver where it can become pyruvate/glucose, donating NH3 back to glutamate, which becomes urea.

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

What is alpha-ketoglutarate critical for?

A

1) Picks up ammonia from aspartate to become glutamate

2) Intermediate in TCA.

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

What does hyperammonemia deplete and lead to?

A

Leads to depletion of alpha-ketoglutarate, leading to inhibition of TCA.

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

What are the symptoms of hyperammonemia?

A

tremor (asterixis), slurring of speech, somnolence, vomiting, cerebral edema, blurring of vision

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

What are the treatments for hyperammonemia?

A

1) limit protein in diet
2) lactulose acidifies the GI tract and tracts NH4+ for excretion
3) Rifaximin decreases colonic ammoniagenic bacteria
4) Benzoate/phenylbutyrate bing amino acid and lead to excretion, can decrease ammonia levels.

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

What is n-acetylglutamate synthase deficiency?

A

N-acetylglutamate is a required cofactor for CAP synthetase I, which brings ammonia into the urea cycle. Absence –> hyperammonemia.

17
Q

How does n-acetylglutamate present? What other deficiency does it look identical to?

A

In infants as poorly regulated respiration and body temperature, poor feeding, developmental delay, intellectual disability; identical to presentation of CAP synthetase I deficiency.

18
Q

What is ornithine transcarbamylase deficiency?

A

Most common urea cycle disorder, X-linked recessive. Ornithine + CAP –> citruline via OTC. Cannot eliminate ammonia, CAP excess converted to orotic acid (pyrimidine synthesis pathway).

19
Q

What are the findings in OTC deficiency?

A

Usually presents in first few days of life, may present later. Increased orotic acid in blood and urine, decreased BUN, sx of hyperammonemia. Diff from orotic aciduria bc no megaloblastic anemia (caused by insufficient pyrimidine).

20
Q

What is the defect in PKU?

A

Phenylketonuria is autosomal recessive defect in phenyalanine hydroxylase or BH4 (malig). Cannot synthesize Tyrosine, building by phenyalanine, excess in urine.

21
Q

Findings of PKU, Treatment:

A

Sx: Intellectual disability, growth retardation, seizures, fair skin, eczema, musty body odor. Newborn screening 2-3 days after birth (normal at birth bc of maternal enzyme).
Tx: Decrease phenylalanine in diet, increase tyrosine. Supplement BH4. Cannot have aspartame (contains phenylalanine).

22
Q

Maternal PKU

A

Lack of proper dietary therapy during pregnancy. Findings in infant: microcephaly, intellectual disability, growth retardation, congenital heart defects.

23
Q

Maple Syrup Urine Disease defect

A

Autosomal recessive blocked degradation of branched amino acids. I Love Vermont = Isoleucine, *Leucine, Valine. Caused by deficient alpha-ketoacid dehydrogenase (b1). Causes increased alpha ketoacids in blood.

24
Q

Maple Syrup Urine Disease findings and treatment

A

Findings: Urine smells like maple syrup. Causes severe CNS defects, intellectual disability, and death. Restriction of Isoleucine, leucine, valine in diet, thiamine (b1) supplementation.

25
Q

Alkaptonuria (ochronosis) defect and findings

A

Auto recess congenital deficiency of homogentisate oxidase in degradative pathway of tyrosine to fumarate. Homogentisic acid accumulates in tissue –> pigment forming.
Sx: dark connective tissue, brown pigmented sclera, urine turns black on prolonged exposure to air. May have debilitating arthralgias (HA toxic to cartilage).

26
Q

What three defects can lead to homocystinuria?

A

1) Cystathionine synthase deficiency (TX: dec met, inc cystine, b12, and folate in diet).
2) Dec affiinity of cystathione synthase for B6 (TX: Inc B6 and cysteine in diet)
3) Homocysteine methyltransferase/methionone synthase deficiency (tx: inc methionone in diet).

27
Q

Findings of homocystinuria?

A

Excess homocysteine in urine, intellectual disability, osteoporosis, marfanoid habitus, kyphosis, lens subluxation (DOWN AND IN), thrombosis, and atherosclerosis (stroke/MI).

28
Q

Cystinuria defect

A

Auto recess hereditary defect of renal PCT and intestinal amino acid transporter that prevents reabsorption of (COLA) cysteine, ornithine, lysine, and arginine.

29
Q

Cystinuria classic presentation

A

Recurrent precipitation of hexagonal cystine (2 cysteines connected by disulfide bond). Urinary cyanide-nitroprusside test is diagnostic. Tx: alkalinize urine (potassium citrate, acetazolamide) and chelating agents (penicillamine). Hydrate.

30
Q

What is the first step of ethanol metabolism?

A

Ethanol to acetaldehyde by Alcohol Dehydrogenase in cytosol.
Produces NADH.
Zero order kinetics.

31
Q

What is the second step of ethanol metabolism?

A

Acetaldehyde to Acetate by Acetaldehyde dehydrogenase to mitochondria.
Produces NADH.

32
Q

What does fomepizole do?

A

Inhibits alcohol dehydrogenase

33
Q

What is fomepizole used for?

A

methanol or ethylene glycol poisoning.

34
Q

What does disulfiram do?

A

Inhibits Acetaldehyde dehydrogenase

35
Q

What does disulfiram cause?

A

Acetaldehyde accumulates

36
Q

What is the limiting reagant for the metabolism of ethanol?

A

B3, NAD+

37
Q

What are the effects of increased NADH/NAD+ ratio in ethanol metabolism?

A

Pyruvate –> lactate (lactic acidosis)
Oxaloacetete –> malate (prevents gluconeogenesis, fasting hypoglycemia)
DHAP –> Glyc-3-P, which combines with fattys –> hepatosteatosis

38
Q

Why does ethanol metabolism favor ketogenesis?

A

Incr NADH disfavors TCA production of more NADH. Acetyl CoA goes to ketones and lipogenesis.