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Emma > Biochem - E4 > Flashcards

Biochem - E4 Flashcards

1
Q

Aa –> acetyl coA

A

Leucine, lysine

Phenylalanine, tyrosine, tryptophan

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2
Q

Aa –> pyruvate

A

alanine, cysteine, glycine, serine, threonine

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3
Q

Aa –> oxaloacetate

A

asparagine –> aspartate –> oxaloacetate.

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4
Q

Aa –> fumerate

A

aspartate, phenylalanine, tyrosine

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5
Q

Aa –> succinyl CoA

A

Isoleucine, methionine, threonine, valine

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6
Q

Aa –> fumarate and acetoacetate

A

Phenylalanine, tyrosine

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7
Q

Branched amino acid breakdown

A

The Breakdown of Branched Chain Amino Acids (Valine, Isoleucine, Leucine) is via aminotransfer to form keto acids, and then the action of a BCAA dehydrogenase

Defective dehydrogenase –> maple syrup urine disease

  • muscle prefers branched, liver has NO branched-chain aminotransferase
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8
Q

Periportal region of liver

A

Converts ammonia to urea

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9
Q

Perivenous region of liver

A

Converts ammonia to glutamine

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10
Q

Some glycogenic amino acids are interconvert with a-Ketoglutarate (via glutamic gamma-semialdehyde)

A 
Arginine *and ornithine 
Proline
Glutamine
Glutamate
--> alpha-ketoglutarate
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11
Q

Propionyl-CoA –> succinyl-CoA requires

A

biotin and vitamin B12

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12
Q

methylmalonate buildup –> dx of

A

methylmalonyl CoA MUTASE defect (due to lack of vitamin B12, or prob w/ absorption w/ intrinsic factor, or prob with conversion to adenosyl form of vitamin B12)

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13
Q

Adenosylcobalamine

A

Vitamin B12 in the adenosyl form –> needed for catabolism of valine, isoleucine, methionine. (all go to propionyl CoA –> succinyl CoA)

Vitamin form would be -OH or -CN

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14
Q

Oxaloacetate pathway

A

Asparagine –> aspartate –> oxaloacetate ( –> PEP –> glucose)

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15
Q

Phenylalanine –> tyrosine rxn

A

Via phenylalanine hydroxylase and tetrahydrobiopterin

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16
Q

dihydrobiopterin –> tetrahydrobiopterin

A

dihydrobiopterin reductase

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17
Q

PKU is due to which deficiency

A

Via phenylalanine hydroxylase deficiency OR due to dihydrobiopterin reductase deficiency

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18
Q

Which aa makes nitric oxide

A

arginine * an essential aa

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19
Q

Tyrosine –> dopa

A

Via tyrosine hydroxylase and tetrahydrobiopterin

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20
Q

Tyrosine –> Dopa —?—> dopamine

A

Via decarboxylase and PLP

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21
Q

? –> thyroxine (T4)

A

Tyrosine + iodine (on thyroglobulin protein) –> thyroxine (thyroid peroxidase)

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22
Q

? –> melanin

A

tyrosine –> melanin. Via tyrosinase (tyrosine-3-monooxygenase)

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23
Q

Albinism

A

tyrosine –> melanin. Via tyrosinase (tyrosine-3-monooxygenase) (defective –> albinism)

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24
Q

Rxns requiring PLP (pyrodoxial phosphate)

A

Aminotransferase rxn –> exchange between keto/amino forms of aa
THF + serine –> glycine + methylene form THF
Dopa –> Dopamine
Homocysteine –> cystathione (–> cysteine)

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25
Q

Gout

A

Increased uric acid in blood

Deficiency in HGPRT, or PRPP synthase, or G-6-Pase deficiency (increased PPS, xs R-5-P)

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26
Q

Tx for gout

A

Allipurinol
^ hypoxanthine analogue, competitive inhibitor of xanthine oxidase.
hypoxanthine and xanthine accumulate –> more soluble than uric acid

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27
Q

Lesch-Nyhan Syndrome

A

lack functional HGPRT (increased uric acid in serum)

  • -> self-mutilation, mental illness and gout like sx
  • Marked increase in the rate of purine biosynthesis by the de novo pathway
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28
Q

SCID

A

ADA (adenosine deaminase deficiency)

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29
Q

Sulfonamides

A

Antibacterial agents. Resemble p-aminobenzoic acid and inhibit synthesis of folate in bacteria, thus unable to form purines and thus their duplication is blocked. Humans not affected by sulfonamides (bc dietary folate).

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30
Q

6-mercaptopurine

A

analogue of hypoxanthine, rely on activation by salvage pathway

After salvage, a potent competitive inhibitor of IMP in the pathways for AMP and GMP biosynthesis.

Once combined with PRPP it acts as a competitive inhibitor of IMP in the pathways for AMP and GMP biosynthesis.

Tx for acute leukemia

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31
Q

Gastric glands

A

secrete Hcl and pepsinogen

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32
Q

Pepsinogen

A

propeptide of pepsin binds at high pH (inside cells, for example)

Pepsin –> active at low pH

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33
Q

Pancreas

A 
Secretes bicarbonate & neutralizes stomach contents  (pH increases to 7 in duodenum) 
Secretes zymogens (trypsinogen, chymotrypsinogen, proelastase, procarboxypeptidase) through pancreatic duct
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34
Q

CCK

A

secreted by cells in the duodenum and stimulates the release of bile into the intestine and the secretion of enzymes by the pancreas.

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35
Q

enteropeptidase

A

secreted by cells of SI, initiates conversion of trypsinogen –> trypsin

36
Q

Enzymes of small intestine

A

trypsin
chymotrypsin
elastase
carboxypeptidase

dipeptase
aminopeptidase

37
Q

Endopeptidases

A
  • Break proteins at peptide bonds, producing short peptides

- trypsin, chymotrypsin, elastase, pepsin

38
Q

Exopeptidase

A
  • Break peptide bonds at N/C regions, producing aa

- carboxypeptidases

39
Q

Trypsin

A

In SI

Binds + aa

40
Q

Villi of SI release…

A

enteropeptidase and also bicarbonate

41
Q

Hereditary pancreatitis

A

mutation in trypsin reduces binding to its inhibitor –> overactive trypsin.
Damages pancreatic tissue and triggers immune response –> inflammation of pancreas

(*or mutation that makes trypsinogen convert too readily to the active trypsin form, or mutations in the inhibitor itself)

42
Q

Intestinal cell transporters

A

aa go in through Na linked transporters specific for aa (cystine and lysine go in through same transporter)

aa go out into blood via facilitated transporters, enter portal vein on way to liver

43
Q

Tryptophan deficiency

A

Hartnup disease

  • loss of tryp bc of defective transporter
  • 4Ds, less severe than pellagra
  • affects brain and skin
44
Q

Niacin

A

(Vit B3)

  • made via tryptophan
  • deficiency: pellagra (4Ds)
  • precursor to NAD and NADP
45
Q

Lysosomal proteases to degrade proteins

A

Cathepsins: effective at degrading extracellular proteins

46
Q

Ubiquitin/Proteasome pathway (UPP)

A

Major path of degrading intracellular proteins

Ubiquitin signals

  1. N-end rule (methionine at end)
  2. Pest sequences (proline, glutamate, serine, threonine) * in protein sequence
  3. destruction boxes
  4. phosphorylation
  5. denaturation/damage
  6. facilitators/chaperones (HPV E6 recruits E6-AP)
47
Q

HPV E6 and p53

A

HPV E6 recruits E6-AP (an E3 ubiquitin ligase) which recognizes and ubiquitinates p53 –> driven to proteasome –> reduced p53 –More rapid cell cycle, increased # cells

48
Q

Parkinson’s

A 
Parkin mutation (parkin=E3 ubiquitin ligase)
or
UCHI mutation (UHCI=deubiquitinase)

tx: L-dopa

49
Q

Kwashiorkor disease

A

insufficient protein/inadequate protein (total calories are OK), start to lose nonessential proteins in body, lose albumin, flaky skin

50
Q

+ N balance

A

pregnancy, muscle building, growth

urea excreted will decrease or not change

Growth due to deposition of protein

51
Q
  • N balance
A

insufficient protein/incomplete dietary protein, trauma

loss of protein due to use of body protein

urea excreted will increase

52
Q

4 forms of N excretion in urine

A

ammonia, urea, creatine, uric acid

53
Q

alpha-ketobutyrate

A

formed by degradation of methionine –> homocysteine –> cystathione –> alpha-ketobutyrate

also formed by de??

54
Q

Synthesis of methionine

A

Homocysteine + methyl form THF –> methionine (via methionine synthase)

55
Q

If methionine is deficient, what else is also deficient?

A

Cysteine (methionine –> homocysteine (via SAM))

56
Q

Which syntheses require tetrahydrobiopterin?

A

Phenylalanine –> tyrosine (via phenylalanine hydroxylase)

Tyrosine –> dopa (tyrosine hydroxylase)

57
Q

Describe the folate trap

A

Methylene form THF –> methyl form THF is IRREVERSIBLE

only other way to get back to THF is through homocysteine + methyl form THF (via methionine synthase and B12) –> methionine + THF

So if B12 deficiency, also secondary deficiency in folate

58
Q

aa only made through 1C transfers

A

glycine
serine
cysteine
methionine

59
Q

Rxns req folate

A

1C transfers between serine and glycine
(serine + THF –> glycine + methylene form THF)

Synthesis of methionine
(homocysteine + methyl form THF –> methionine + THF) via methionine synthase

De novo purine synthesis

60
Q

Path to phosphocreatine (ATP reservoir in muscle)

A

arginine –> glycine –SAM–> creatine –> phosphocreatine

can react with ADP to form ATP
OR
can convert to –> creatinine (*indicator of renal function)

61
Q

Homocystinuria

A

Due to cystathione synthase defect

increased homocystine in urine

tx: supposed B6 (PLP), choline/betaine, folate, restrict methionine (low protein diet)

62
Q

_________ conjugation with serine generates cystathione

A

homocysteine

63
Q

CPSII

A

(1st step, pyrimidine biosynthesis)
glutamine + HCO3- + 2 ATP –> carbamoyl phosphate

Stim via PRPP and ATP
Inhib via UTP, UMP *allosteric inhib

64
Q

Origins of pyrimidine ring

A

glutamine amide, aspartate, HCO3-

65
Q

Origins of purine ring

A

glutamine, glycine, THF, aspartate

66
Q

Enzymes of pyrimidine synthesis

A 
CPSII*
aspartate transcarbamoylase
dihydroorotase
dihydroorotate dehydrogenase
orotate phosphoribosyl transferase
orotate phosphoribosyl decarboxylase**
UMPK
nucleoside diphosphate kinase
CMP synthase
67
Q

orotate phosphoribosyl transferase
orotate phosphoribosyl decarboxylase

Regulation and deficiency

A

Inhibition via UMP

Absence –> orotic aciduria (orotic acid excreted, severe anemia, failure of normal growth

68
Q

Salvage pathway of pyrimidine synthesis

A

Base –> NS –> NT

Pyrimidine –phosphorylase–> pry-ribose –kinase–> pyr-ribose-phosphate

69
Q

Pyrimidine catabolism enzymes

A

NT–> NS –> base
*yields soluble prods

phosphatase
cytosine deaminase (cytidine–>uridine)
pyrimidine NS phosphorylase

70
Q

Deoxyribonucleotide synthesis

A

Via ribonucleotide reductase (removing 2’OH of ribose of nucleotide diphosphates)
G/A/U/C-DP –> dG/A/U/C-DP

Uses NADPH

71
Q

Buildup of dATP

A

SCID (bc dATP buildup inhibits ribonucleotide reductase)

72
Q

Thymidine synthesis

A

dUMP –> dTMP (via thiamine synthase)

req. Methylene THF

73
Q

fDUMP

A

Covalent binding of FdUMP to thymidylate synthatase inactivates the enzyme. (F –> very electroneg)

Useful for chemo

74
Q

Methotrexate

A

Folate analogue
Competitive inhibitor of dihydrofolate reductase
–> cant regenerate THF –> prevents tumor growth

75
Q

Hydroxyurea

A

Inhibitor of tyrosine radical of ribonucleotide reductase (inhibits tyrosine radical)

76
Q

Insulin vs. glucagon (glycolysis regulation)

A

Insulin –> PFK2 activated –> more F26BP –> stim PFK1 –> glycolysis

Glucagon –>cAMP –> PKA –> inhib PFK2 –> less F26BP-> inhib PFK1 –> inhib glycolysis, promote gluconeogenesis

77
Q

Insulin vs. glucagon (hormone-sensitive lipase regulation)

A

Insulin decreases HSL (increases lipid deposition)

Glucagon increases HSL (increases mobilization of FA to circulation to be used by muscle, etc)

78
Q

aa used to make creatine

A

methionine, arginine, glycine

79
Q

Increased homocysteine –> increased arterial disease

Admin with what will reduce homocysteine levels?

A

Folate

80
Q

Purine catabolism enzymes

A

NT–> NS –> base + R-1-P

phosphatase
adenosine deaminase
purine nucleotide phosphorylase

81
Q

polyamines

A

exp. spermine, binds DNA

82
Q

Most of the ammonia used by CPSI comes from…

A

from glutamate or glutamine through the action of glutamate dehydrogenase and glutaminase, which are both present in liver mitochondria

83
Q

The two atoms of N of urea enter the cycle at two points…

A

One as carbamoyl phosphate synthesized from free ammonia, the other as the amino group of aspartate:

84
Q

NAG is synthesized from …

^ synthesis is stimulated by…

A

acetyl CoA and glutamate

stimulated by arginine

85
Q

serine dehydratase

A

serine –> pyruvate

releases free ammonia

86
Q

What directly provides carbon skeleton in cysteine synthesis?

A

SERINE

Emma (18 decks)

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