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Biochemistry III > Final: Diseases + Their Causes (Ben) > Flashcards

Final: Diseases + Their Causes (Ben) Flashcards

1
Q

What is the molecule responsible for transport of cholesterol into mitochondria?

What is the disease which results from a deficiency of it?

A

stAR protein

  • congenital lipoid adrenal hyperplasia
  • adrenal cortex accumulates lipids bc it can’t use them for hormone synth… if the deficiency/mutation is severe enough, will result in death
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2
Q

What is a condition which results from a problem with pre-receptor specificity?

And its cause?

(in relation to steroid hormones)

A

Apparent Mineralocorticoid Excess

  • lack of 11B-OH-SDH-2 which normally converts cortisol to inactive cortisone in mineralocorticoid target cells
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3
Q

What condition results when the usual negative feedback mechanism acting on hypothalamic/pituitary control of the adrenal cortex is compromised?

How is it compromised?

A

Congenital Adrenal Hyperplasia

  • usually a lack of 21-OHase** or **11-OHase activity which leads to cortisol deficiency
  • without cortisol to inhibit ACTH, the adrenal cortex is stimulated and hyperplasia results
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4
Q

What is the condition of excess cortisol called?

Symptoms?

A

Cushing Syndrome

  • symptoms basically relate to cortisol effects
  • impaired glucose tolerance
  • visceral obesity
  • muscle atrophy
  • osteoporosis
  • infections (due to immunosuppression)
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5
Q

What is the common condition resulting in ovarian cysts?

How does it occur?

What non ovary-related symptoms is it associated with?

A

Polycystic Ovarian Syndrome

  • via hyperandrogenism when theca cells increase + express more LH receptors —> androgen increase
  • causes lack of ovulation and antral follicle retention (=cysts)
  • associated with obesity + insulin resistance
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6
Q

Which nitrogen metabolism issue stems from deficiency of the rate-limiting enyzme in the urea cycle?

(And from the enzyme right after that step?)

How are they treated (4 ways)?

A

Hyperammonemia Type I

  • via Carbamoyl Phosphate Synthase I (CPT I)

( Type II from Ornithine Transcarbamoylase )

  1. low protein diet
  2. inhibit colonic NH3 production (via antibiotics)
  3. AA binders (benzoate-Gly or phenylacetate-Glu)
  4. replace intermediates of cycle
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7
Q

What can result from folate/B12 deficiency and why?

A
  • Lacking either can interrupt the SAM cycle (folate = H4F precursor, B12 = Hcy Methyltransferase prosth. grp.)
  • Results in:
    • High adenosine + Hcy in blood
    • “Methyl Trap” - methyls get “stuck” on H4F b/c they can’t be used in SAM cycle, so less H4F can be used for nucleotide synth (= inhib cell division)
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8
Q

What can result from a deficiency in a cysteine synthesis enyzme?

A

Cystathionine Synthase Deficiency can result in a buildup of homocysteine and possible atherosclerosis

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9
Q

What deficiency results in a build-up of acidic intermediates of succinyl-CoA synthesis from AAs?

A

B12 or Methylmalonyl-CoA Mutase deficiency

  • both enzyme and co-factor are needed to convert mm-CoA to succinyl-CoA
  • deficiency –> methylmalonic aciduria
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10
Q

What disease results from deficiency of an enyzme needed for propionyl-CoA formation?

A

Maple Syrup Urine Disease

  • deficiency of BC-α-KA Dehydrogenase
  • results in high BCKAs in urine (maple syrup smell)
  • leads to ketoacidosis and retardation
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11
Q

What can result from an inability to break down Ser and Gly?

A

Non-ketotic Hyperglycinemia

  • lack of glycine cleavage complex results in Gly buildup
  • causes mental retardation and death because Gly is an inhibitory NT
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12
Q

Which disease results from lack of an enyzme for conversion of one aromatic AA to another?

A

Phenylketonuria

  • Phenylalanine Hydroxylase deficiency
  • treated with low Phe diet
  • results in phenyl-pyruvate/-lacate/-acetate in urine
  • ketoacidosis and mental retardation result
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13
Q

What enzyme deficiency in which tissue might results in cramps without obvious signs of elevated ammonia or urate?

A

AMP deaminase in muscle

  • because AMP buildup will cause cramping but the deaminase enyzmes products of ammonia (directly) and urate (after liver processing of IMP’s inosine) will not elevate
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14
Q

What deficiency of a purine salvage enyzme leads to cognitive disabilites?

What other symptoms?

What abt the genetics of the disease?

A

Lesh-Nyhan Syndrome

  • HGPRT deficiency
    • hypoxanthine-guanine P-ribosyl transferase
  • leads to retardation, aggression, selfmutilation and hyperuricemia
  • is an X-linked trait
  • (due to GTP deficiency in basal ganglia)
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15
Q

Deficiency of enzymes of purine nucleotide catabolism can lead to what?

(specific enzymes, symptoms, treatment)

A

“Non-HIV AIDS”

  • adenosine deaminase** and/or **purine nucleotide phosphorylase
  • Symptoms:
    • T-cell deficiency
    • increased adenosine –> increased dATP
      • inhibits ribonucleotide reductase, DNA synthesis, cell division
  • Treatment:
    • ADA enzyme treatment
    • gene therapy
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16
Q

What are the 4 possible causes of hyperuricemia?

A
  1. PRPP Overproduction
    • PRPP synthase allosteric site mutation = no inhibition via AMP/GMP
    • overproduction of R-5-P via Von Gierke disease -> incr. G6P -> incr. PPP
  2. Purine Salvage Deficiency
    • ex: Lesh-Nhyan (HGPRT defic.) –> incr. base catabolism
  3. Disturbed ATP Metabolism
    • ​exercise or fructose intolerance (phosphate trap)
  4. Secondary Reasons
    • ​​tissue damage, chemotherapy –> DNA breakdown + purine overproduction
17
Q

What is the main symptom hyperuricemia?

And treatment?

A
  • Symptoms:
    • Na-urate crystals (“tophi”) in joints due to low urate solubility (esp. at low pH)
  • Treatment:
    • Allopurinol - hypoxanthine analog which inhibits xanthine oxidase so that bases are excreted (rather than urate)
18
Q

What enzyme deficiencies can lead to an excretion of pyrimidine synthesis intermediates in the urine?

What’s the condition called?

A

Orotic Aciduria

  • 2 enyzmes:
    • UMP Synthase (Orotate P-Ribosyl Transferase + OMP Decarboxylase)
      • ​can be deficiency or inhibition by allopurinol (gout) / 6-azauridine (cancer) treatment … treated with oral uridine
    • Ornithine Transcarbamoylase
      • ​CAD enyzmes re-route built up Carbamoyl-P from urea cycle and overproduces orotate
19
Q

What are some of the symptoms of orotic aciduria?

Treatment?

A
  • megaloblastic anemia - resistant to B12/folate treatment
  • DNA/RNA synthesis issues - mental/physical retardation

Treatment:

  • Oral uridine can bypass the enzyme deficiencies and allow formation of UMP etc.
20
Q

What does a deficiency of the non heme-inhibited form of the main heme synthesis enzyme result in?

(this is probably a less important one…)

A

Sideroblastic Anemia

  • a hypochromic anemia due to ALA Synthase E (marrow isoform) deficiency
  • this isoform is stimulate by EPO but not inhibited by heme like the liver isoform
21
Q

What results from issues with pumping heme degradation products out of the liver?

What 2 mechanisms can cause this?

A

Post-hepatic Jaundice / Direct Hyperbilirubinemia

  • means conjugation is working, but liver secretion is not
  • Mechanisms:
    1. Obstructred bile duct
    2. Dysfunctional MRP2 transporter (Dubin-Johnson/Rotor Syndrome)
  • conjugated bilirubin increases in urine/plasma
22
Q

What results from abnormal increases in the amount of heme which must be degraded?

A

Prehepatic Jaundice

  • caused by anything which increases hemolysi__s and thus heme breakdown
    • sickle cell anemia, Pyr Kinase deficiency, G6P DH deficiency
  • a form of indirect (unconjugated) hyperbilirubinemia
    • _​_increased heme degradation overwhelms bilirubin conjugation capacity of liver
  • increased unconj. bilirubin in blood
23
Q

What results from issues with bilirubin conjugation in the liver?

What general condition and what two specific diseases?

A

Hepatic Jaundice

  • a form of Indirect (Unconjugated) Hyperbilirubinemia
  1. Crigler-Najjar Syndrome (Type I)
    • congenital non-hemolytic jaundice
    • total UDP-glucuronosyl transferase deficiency
    • Phenobarbitol induces conjugation in partial deficiency (type II) but useless in type I
  2. Gilbert’s Disease​
    • ​slightly reduced transferase activity, 5% of people, anti-oxidant capacity of increased bilirubin can be beneficial
24
Q

3 important heme synthesis diseases result from deficiencies of enzymes along the aminolevulinate –> heme pathway.

What are they, their symptoms, etc.?

A
  1. Acute Intermittent Porphyria
    • ​Porphobilinogen Deaminase deficiency
    • urine darkens on exposure, incr. urine δ-ALA and porphobilinogen
  2. Congenital Erythropoietic Porphyria
    • ​​Uroporphyrinogen II Synthase deficiency
    • uro/coproporphyrinogen I in urine, photosensitivity
  3. Porphyria Cutanea Tarda
    • ​​Uroporphyrinogen Decarboxylase deficiency
    • uroporph III buildup in skin, photosensitivity
  • main symptoms of all are neuropsychiatric issues, fluorescent teeth, red urine and photosensitivity
  • can treat with hemin, a heme analog
25
Q

What is an autoimmune attack of nicotinic receptors called?

What occurs?

What is the first symptom of this?

A

Myasthenia gravis

The number of receptors is decreased because their degradation is accelerated, plus existing receptors are blocked by antibodies

First symptom of this is fatigue, which progressively gets worse

26
Q

What condition results from mutation of the RYR1** receptor?

A

Malignant hyperthermia

Calcium continuously leaks from the SR, causing muscle rigidity

Other effects: accelerated metabolism (because some citric acid cycle enzymes are stimulated by calcium: pyruvate dehydrogenase, alphaketoglutarate dehydrogenase, and isocitrate dehydrogenase)

27
Q

Mutations of what protein causing what syndrome can lead to prolonged ventricular action potential/fibrillation/death?

A

Mutations of KCNQ1, hERG (a VD K+ channel) can lead to…

Long QT Syndrome

(b/c these channels normally repolarize ventricular myocytes)

28
Q

What can result from a mutation of the ion channels which control the pancreas’ regulation of blood sugar?

A

Persistent Hyperinsulemic Hypoglycemia

  • ATP-sensitive K+ channel mutation:
    • channel is constantly shut -> cell is depolarized -> insulin is secreted
  • some patients respond to K+ channel opener diazoxide
29
Q

Where is the ClC-0 Cl- channel important?

What can its mutation result in?

A

In skeletal muscle where it stabilizes resting membrane potential.

Mutation can result in myotonia because muscle fiber hyperactivity results from an unstable membrane potential.

30
Q

What is the condition in which a tumor in the adrenal medulla overproduces a neurotransmitter?

What can be used to treat it and how?

A

Pheochromocytoma

  • overproduces NE
  • alpha-methyl-P-tyrosine** can be used to inhibit **tyrosine hydroxylase the first enzyme in NE synthesis from Tyr
31
Q

Disturbed levels of what metabolite found in the urine can indicate CNS noradrenaline dysfunction?

And PNS noradrenaline dysfunction?

A
  • MHPG (CNS)
    • 3-methoxy-1-hydroxy-phenylglycol
    • measured in urine (or CSF)
  • VMA (PNS)
    • vanillylmandelic acid
    • high levels can indicate pheochromocytoma
32
Q

Disturbed levels of what dopamine metabolite in the urine can indicate dopamine-related pathologies?

A

Homovanillic Acid

  • goes up in schizophrenia
  • goes down in Parkinson’s
33
Q

Deficiency of what clotting factor leads to hemophilia A?

A

Factor VIII

34
Q

What disease results from deficiency of an enzyme which breaks down monomers which have been removed from glycogen?

A

Von Gierke Disease

  • lack of G6P Phosphatase
  • glycogen accumulates
  • hypoglycemia, ketosis, lactic acidemia and hyperlipemia
  • type Ia is lack of enzyme, type Ib is lack of transporter for G6P into ER
35
Q

What disease results from lack of a glycogen breakdown enzyme in muscle?

A

McArdle Disease

  • no muscle glycogen phosphorylase

Biochemistry III (35 decks)

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