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Step 1 > Biochem - metabolism > Flashcards

Biochem - metabolism Flashcards

1
Q

Metabolism that happens specifically in mitochondria

A 
Fatty acid oxidation
acetyl-Coa production
TCA cycle
oxidative phosphorylation
ketogenesis
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2
Q

ATP production in malate-aspartate shuttle vs. G3P shuttle

A

Electrons moved to ETC b/c NADH can’t cross membrane

Malate-aspartate shuttle: utilizes malate, creates 32 ATP (heart, liver)

G3P shuttle: utilizes G3P, creates 30 ATP since electrons delivered directly to complex 2 (skeletal muscle)

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3
Q

Key enzymes in glycolysis

A

Hexokinase/glucokinase

PFK-1 (incr. by F26BP)

Pyruvate kinase

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4
Q

Regulation by F26BP

A

incr. F26BP = more glycolysis, less gluconeogenesis

less F26BP = less glycolysis

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5
Q

Two complexes in glycolysis and TCA cycle that are similar

A

Pyruvate dehydrogenase and alpha-ketoglutarate dehydrogenase

use same cofactors, similar substrates and actions

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6
Q

PDH complex deficiency

A

X-linked, causes pyruvate shunting to lactate and alanine starting in infancy

tx: incr. lysine/leucine intake! ketogenic nutrients/high fat content

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7
Q

Four possible endpoints for pyruvate

A
  1. ) alanine: ALT, B6
  2. ) oxaloacetate: pyruvate carboxylase, biotin
  3. ) acetyl-CoA: PDH, B1/2/3/5
  4. ) lactate: LDH, B3
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8
Q

ETC inhibitors

A

decr. proton gradient

cyanide, carbon monoxide, antimycin A, rotenone

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9
Q

Uncoupling agents

A

Disconnects ETC from O2 consumption

Generates free heat

2,4-dinitrophenol (weight loss), aspirin, thermogenin

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10
Q

Four main gluconeogenesis enzymes

A

Pyruvate carboxylase (makes oxaloacetate)
PEP carboxykinase (OAA to PEP)
Fructose-1,6-bisphosphatase
Glucose-6-phosphatase

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11
Q

Odd-chain fatty acids

A

produce 1 propionyl-CoA, which enters TCA, then gluconeogenesis, thus a source of glucose

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12
Q

Uses of NADPH

A

glutathione reduction in RBCs

fatty acid and cholesterol/steroid synthesis

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13
Q

Location of HMP shunt

A

RBCs (glutathione reduction

lactating mammary glands, liver, adrenal cortex (fatty acid/steroid synthesis)

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14
Q

G6P DH deficiency

A

decr. NADPH in RBCs

hemolysis precipitated by oxidizing agents or infections (from inflammatory response)

random: incr. malarial resistance

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15
Q

Fructokinase vs. aldolase B deficiency

A

Essential fructosuria - asx

Fructose intolerance - incr. F-1-P, decr. free PO4, decr. GNG. Sx present after sugar consumption (jaundice, cirrhosis, vomiting), incr. fructose in urine

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16
Q

Galactokinase vs. galactose-1-phosphate uridyltransferase deficiency

A

Galactokinase deficiency - mild condition, infantile cataracts

Classic galactosemia - failure to thrive, jaundice, hepatomegaly, ID, E. coli sepsis

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17
Q

Enzymes in sorbitol metabolism

A

Aldose reducatase: glucose to sorbitol

Sorbitol dehydrogenase: sorbitol to fructose

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18
Q

Aldose reductase only locations

A

Schwann cells, retina, kidneys, lens

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19
Q

Findings in lactase deficiency

A

Stool: decr. in pH

Breath: incr. H content

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20
Q

Urea cycle key steps

A

Carbamoyl phosphate: in mito, converts CO2 + NH3 to carbamoyl phosphate
OTC: combines CP with ornithine to make citrulline
Citrulline + aspartate/ATP = argininosuccinate
Loss of fumarate = arginine
Arginase makes ornithine again! This is loss of UREA

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21
Q

Components of urea

A

1 NH3
1 CO2
1 Aspartate

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22
Q

Path of ammonia from amino acids to excretion

A

Muscle: amino acids –> glutamate –> alanine

Cori or Cahill cycle: muscle to liver (requires alanine and lactate)

Liver: alanine –> glutamate –> urea

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23
Q

Urea cycle deficiencies

A

N-acetylglutamate synthase deficiency: leads to hyperammonemia (required cofactor for carbamoyl phosphate synthetase)

OTC deficiency: X-linked recessive, look for orotic aciduria w/o megaloblastic anemia

24
Q

Defects in amino acid metabolism

A 
Phenylketonuria
Maple syrup urine disease
Alkaptonuria
Homocystinuria
Cystinuria
25
Q

Intellectual disability, seizures, fair skin, musty body odor

A

Phenylketonuria - decr. phenylalanine hydroxylase (decr. Phe to Tyr)

tx: tyrosine supplementation, avoid aspartame (Phe)

26
Q

Severe CNS defects, death, urine smells like burnt sugar

A

Maple syrup urine disease - blocked degradation of branched amino acids (isoleucine, leucine, valine)

decr. alpha-ketoacid dehydrogenase
tx: thiamine supplementation and restrict isoleucine, leucine, valine in diet

27
Q

Dark connective tissue, brown sclerae, urine turns black on expsoure to air

A

Alkaptonuria - def. of homogentisate oxidase in the degradative pathway of tyrosine to fumarate

Homogentisic acid accumulates in tissues

28
Q

Osteoporosis, marfanoid habitus, kyphosis, lens subluxation

A

Homocystinuria

    • cystathione synthase (B6 enzyme) deficiency (leads to decr. cysteine and incr. methionine)
    • homocysteine methyltransferase (B12 enzyme) deficiency (leads to decr. methionine)
29
Q

Recurrent hexagonal kidney stones, positive urinary cyanide-nitroprusside test

A

Cystinuria - defect in renal PCT/intestinal reabsorption of Cysteine, Ornitihine, Lysine, Arginine

tx: potassium citrate/acetazolomide, chelating agents

30
Q

Homocyteine products

A

Homocysteine methyltransferase - converts to methionine using B12

Cystathione synthase - converts to cystathione using B6

31
Q

Stimulators of glycogenolysis

A

Glucagon (incr. cAMP, PKA)

Epinephrine alpha and beta receptors (incr. cAMP, PKA)

32
Q

Stimulators of glycogen synthesis

A

Insulin (tyrosine kinase receptor, phosphorylation of glycogen synthase)

33
Q

Glycogen breakdown

A

Muscle - glycogen to G6P (uses phosphoglucomutase) to enter glycolysis

Liver - Glycogen phosphorylase, debranching enzymes cleaves off in orderly pattern

34
Q

Glycogen storage diseases

A

Type I: Von gierke (glucose-6-phosphatase)
Type II: Pompe (acid maltase)
Type III: Cori (debranching)
Type IV: McArdle (skeletal muscle glycogen phosphorylase)

35
Q

Severe fasting hypoglycemia, incr. glycogen in liver (hepatomegaly), incr. TGs, lactic acidemia

A

Von gierke - glucose-6-phosphatase

tx: frequent oral glucose/cornstarch, avoid fructose/galactose

36
Q

Hypertrophic cardiomyopathy, cardiomegaly, exercise intolerance, early death

A

Pompe - acid maltase

Pompe trashes the pump

37
Q

Fasting hypoglycemia with normal lactate levels

A

Cori - debranching enzyme

Gluconeogenesis intact

38
Q

Painful muscle cramps, myoglobinuria, arrhythmia from electrolyte disturbances

A

McArdle (skeletal muscle phosphorylase)

Blood glucose levels are unaffected

McArdle = muscle

Tx: B6 supplementation

39
Q

HSM, pancytopenia, aseptic necrosis of femur, bone crises, Gaucher cell (lipid-laden macs, tissue paper)

A

Gaucher disease - glucocerebridase

accum of glucocerebroside

40
Q

Progressive neurogeneration, foam cells, cherry-red macula, HSM

A

Niemann-Pick disease - sphingomyelinase

accum of sphingomyelin

41
Q

Progessive neurodegeneration, developmental delay, cherry-red macula, onion skin lysosomes, NO HSM

A

Tay-Sachs disease - hexosiaminidase A

NOTE: NO HEPATOMEGALY!

42
Q

Optic atrophy, globoid cells, peripheral neuropathy

A

Krabbe disease - galactocerebridase

43
Q

Hurler vs. Hunter syndrome

A

Mucopolysaccharides

Hurler - corneal clouding, airway obstruction
Hunter - no corneal clouding, aggressive behavior

44
Q

Citrate shuttle

A

used in fatty acid synthesis to move citrate from mitochondria to the cytosol

sytrate = synthesis

45
Q

Carnitine shuttle

A

used to move fatty acyl-CoA from the cytosol to the mitochondria

carnitine = fatty acyl carnage

46
Q

Minor illness leading sudden death, liver dysfunction, present in infancy or early childhood with vomiting

A

MCAD deficiency

accumulation of 8 to 10 carbon fatty acyl carnitines in the blood

leads to hypoketotic hypoglycemia***

47
Q

Causes of ketogenesis

A

prolonged starvation or diabetes - depletion of oxaloacetate for gluconeogenesis

alcoholism - excess NADH shunts oxaloacetate to malate

48
Q

Fat sources for gluconeogenesis

A

Odd-chain FFAs

Adipose tissue glycerol

49
Q

LPP that mediates remnant uptake (extra remnantsq

A

Apo-E

50
Q

LPP that activates LCAT

A

Apo-A1

51
Q

LPP that serve as lipoprotein lipase cofactor

A

Apo-C2

52
Q

LPP that mediates chylomicron secretion

A

Apo-B48

53
Q

LPP that binds LDL receptor

A

Apo-B100

54
Q

Xanthomas, pancreatitis, HSM, creamy layer in supernatant

A

Type I hyperchylomicronemia

lipoprotein lipase deficiency

55
Q

Accelerated atherosclerosis, tendon xanthoma, corneal arcus

A

Type II hypercholesterolemia

absent/defective LDL receptor

56
Q

Hepatic overproduction of VLDL

A

Type IV hypertriglyceridemia

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