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Biochem > Metabolism > Flashcards

Metabolism Flashcards

1
Q

Mitochondria reactions

A

BOAT - B-oxidation, Oxidative phosphorylation, Acetyl-coA production, and TCA cycle

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2
Q

Cytoplasm and mitochondria reactions

A

HUGs take two (Heme synthesis, Urea cycle, Gluconeogenesis)

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3
Q

Glycolysis rate limiting enzyme

A

PFK-1 — increased by AMP and fructose-2,6-bisphosphate — decreased by ATP and citrate

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4
Q

Gluconeogenesis rate limiting enzyme

A

Fructose - 1,6-bisphosphatase – increased by ATP and acetyl-coA — decreased by AMp and fructose-2,6-bisphosphate

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5
Q

TCA cycle rate limiting enzyme

A

Isocitrate dehydrogenase – increased by ADP – decreased by ATP and NADH

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6
Q

Glycogenesis rate limiting enzyme

A

Glycogen synthase – increased by G6P, insulin, cortisol — decreased by epinephrine, glucagon

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7
Q

Glycogneolysis rate limiting enzyme

A

Glycogen phosphorylase – increased by epinephrine, glucagon, and AMP — decreased by G6P, insulin, ATP

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8
Q

HMP shunt rate limiting enzyme

A

G6PD - increased by NADP — decreased by NADPH

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9
Q

De novo purine synthesis rate limiting enzyme

A

PRPP – decreased by AMP, inosine monophosphate, and GMP

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10
Q

De novo pyrmidine synthesis rate limiting enzyme

A

Carbamoyl phosphate synthetase II — increased by ATP, decreased by UTP

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11
Q

Urea cycle rate limiting enzyme

A

Carbamoyl phosphate synthetase I — increased by N-acetylglutamate

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12
Q

Fatty acid synthesis rate limiting enzyme

A

Acetyl-CoA carboxylase — increased by insulin and citrate — decreased by glucagon and palmitoyl CoA

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13
Q

Fatty acid oxidation rate limiting enzyme

A

Carnitine acyltransferase I — decreased by malonyl-coA

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14
Q

Ketogenesis rate limiting enzyme

A

HMG-CoA synthase

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15
Q

Cholesterol synthesis rate limiting enzyme

A

HMG-CoA reductase — increased by insulin and thyroxine — decreased by glucagon and cholesterol

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16
Q

Heme synthesis rate limiting enzyme

A

Aminoleuvulonate snythase

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17
Q

Bile acid synthesis rate limiting enzyme

A

7a-hydroxylase

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18
Q

ATP production

A

Aerobic metabolism makes 32 net ATP via malate aspartate shuttle (heart and liver), and 30 net ATP via glycerol-3-phosphate shuttle (muscle) — anaerobic only makes 2 net ATP (erythrocytes)

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19
Q

Universal electron acceptors

A

Nicotinamids and flavin molecules — NAD is used in catabolic processes — NADPH used in anabolic processes

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20
Q

Hexokinase

A

Located in most tissues except liver and B cells of pancreas — lower Km (higher affinity), lower Vmax (lower capacity) — feedback inhibited by G6P — steady state

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21
Q

Glucokianse

A

Liver, B cells of pancreas — higher Km (lower affinity), higher Vmax (higher capacity) — induced by insulin — gene mutation associated with maturity onset diabetes of the young – works at high glucose concentrations

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22
Q

Glycolysis reactions that require ATP

A

Glucose to G6P (G6P inhibits hexokinase, F6P inhibits glucokinase) and Fructose-6-P to Fructose-1,6-BP

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23
Q

Glycolysis reactions that produce ATP

A

1,3-BPG to 3-PG (and vice versa – Phosphoglycerate kinase) — PEP to pyruvate (Pyruvate kinase – increased by fructose-1,6-BP, decrased by ATP and alanine)

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24
Q

Fructose-2,6-BP regulation

A

Fasting state: increased glucagon –> increased cAMP –> increased protein kinase A –> increased FBPase-2, decreased PFK2, less glycolysis and more gluconeogensis

Fed state: increased insulin –> decreased cAMP –> decreased protein kinase A –> decreased FBPase-2, increased PFK2, less gluconeogensis, more glycolysis

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25
Q

Pyruvate dehydrogenase complex

A

Links glycolysis to TCA cycle — 5 cofactors (Tender Loving Care For Nancy): pyrophosphate (B1, thiamine, TPP), FAD (B2, riboflavin), NAD (B3, niacin), CoA (B5, pantothenic acid), and lipoic acid (inhibited by arsenic) — complex is activated by exercise — deficiency leads to buildup of pyruvate leading to increased lactate (via LDH) and alanine (via ALT): neurologic defects, lactic acidosis, increased serum alanine - Tx: increase intake of ketogenic nutrients (lysine and leucine)

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26
Q

Pyruvate metabolism

A

Alanine (alanine aminotransferase requires B6) — Oxaloacetate (pyruvate carboxylase requires biotin) — Acetyl-coA (pyruvate dehydrogenase requires B1, B2, B3, B5, lipoic acid) — Lactate (lactic acid dehydrogenase requires B3)

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27
Q

TCA cycle products

A

3 NADH, 1 FADH2, 2 CO2, 1 GTP per acetyl coA = 10 ATP (all times 2 per glucose) – all reactions in mitochondria — order of molecules: Citrate Is Kreb’s Starting Substrate For Making Oxaloacetate

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28
Q

Electron transport ATP production and poisons

A

1 NADH (2.5 ATP) and 1 FADH2 (1.5 ATP) — Electron transport inhibitors (Rotenone, cyanide, antimycin A, CO) — ATP synthase inhibitors (oligomycin) — uncoupling agents (increase membrane permeability, leading to decreased proton gradient, no ATP synthesis but heat is produced - 2,4 dinitrophenol - aspirin - thermogenin in brown fat)

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29
Q

Gluconeogensis, irreversible enzymes

A

Pathway Produces Fresh Glucose — Pyruvate carboxylase (mitochondria), PEP carboxykinase (cytosol), Fructose-1,6-BP (cytosol), Glucose-6-phosphatase (ER) — occurs mostly in liver — odd chain fatty acids make 1 propionyl-coA that can enter the TCA and undergo gluconeogenesis (glucose source)

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30
Q

HMP shunt

A

Source of NADPH (glutathione reduction inside RBCs, fatty acid and cholesterol biosynthesis) — all reactions occur in cytoplasm — occurs in lactating mammary glands, liver, adrenal cortex, and RBCs — oxidative (irreversible) has G6P to 2 NADPH and Ribulose-5-P via G6PD —- Nonoxidative (reversible has Ribulose-5-P to Ribose-5-P, GLyceraldehyde-3-P, Frucose-6-P via Phosphopentose isomerase and transketolases (requires B1)

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31
Q

G6PD deficiency

A

NADPH is necessary to keep glutathione reduced, detoxifies free radicals and peroxides (decreased NADPH in RBCs leads to hemolytic anemia - due to drugs, infection, or fava beans) — X linked recessive disorder – Heinz bodies and bite cells

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32
Q

Essential fructosuria

A

Defect in fructokinase - autosomal recessive - benign, asymptomatic – frucose in blood and urine

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33
Q

Fructose intolerance

A

Deficiency of aldolase B - autosomal recessive – Fructose-1-P accumulates causing a decrease in phosphate leading to an inhibition of glycogenolysis and gluconeogenesis — symptoms following fruit, juice, or honey – urine dipstick will be negative (only tests for glucose) but can see reducing sugar in urine — Hypoglycemia, jaundice, cirrhosis, vomiting — decrease fructose and sucrose intake

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34
Q

Galactokinase deficiency

A

Galactitol accumulates, relatively mild, autosomal recessive — galactose in blood and urine, infantile cataracts

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35
Q

Classic galactosemia

A

Absence of galactose-1-phopshate uridyltransferase — autosomal recessive – damage caused by accumulation of toxic substances — failure to thrive, jaundice, hepatomegaly, infantile cataracts, intellectual disability — exclude galactose and lactose

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36
Q

Sorbitol

A

Traps glucose in the cell via aldose reductase — can be converted to fructose in liver/ovaries/seminal vesicles via sorbitol dehydrogenase — Schwann cells, retina, and kindneys have a risk for osmotic damage (cataracts, peripheral neuropathy) due to sorbitol accumulation – common in chronic diabetics

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37
Q

Lactase deficiency

A

Lactose intolerance — loss of brush border due to gastroenteritis, autoimmune disease, etc. — stool has decreased pH and increased osmotic gap, breath shows increased hydrogen content – osmotic diarrhea - avoid dairy

38
Q

Essential amino acids

A

Glucogenic (methionine, valine, histidine) — Glucogenic/ketogenic (isoleucine, phenylalanine, threonine, tryptophan) — Ketogenic (leucine, lysine)

39
Q

Acidic amino acids

A

Aspartic acid and glutamic acid

40
Q

Basic amino acids

A

Arginine, lysine, histidine

41
Q

Urea cycle substrates

A

Ordinarily, Careless Crappers Are Also Frivolous About Urination — Excess nitrogen is converted to urea and excreted by kidneys – any urea cycle disorder has protein restriction as treatment

42
Q

Hyperammonemia

A

Excess NH4, which depletes aKG leading to inhibiton of TCA cycle, decreased glutamate –> increased glutamine –> astrocyte swelling and dysfunction —- tremor, slurring of speech, vomiting, cerebral edema – Tx: limit protein, lactulose (acidify GI tract and trap NH4 for excretion), Rifaximin (decrease colonic bacteria), Benzoate or phenylbutyrate (decrease ammonia levels)

43
Q

N-acetylglutamate syntahse deficiency

A

Cofactor for carbamoyl phosphate synthetase I –> hyperammonemia — presents in neonates as poorly regulated respiration and body temp, poor feeding, developmental delay

44
Q

Ornithine transcarbamylase deficiency

A

x-linked recessive — excess orotic acid in blood and urine, decreased BUN, symptoms of hyperammonemia

45
Q

Phenylalanine convers to

A

Requires B4 –> Tyrosine (then Thyroxine) –> Dopa (requires B4, then Melanin) –> Dopamine (requires B6) –> NE (requires vitamin C) –> Epi (requires SAM)

46
Q

Tryptophan converts to

A

Niacin with B6 or Serotonin with BH4 and B6

47
Q

Histidine converts to

A

Histamine with B6

48
Q

Glycine converts to

A

Porphyrin with B6 –> Heme

49
Q

Glutamate converts to

A

Glutathione or GABA with B6

50
Q

Arginine converts to

A

Creatinine, urea, or nitric oxide (BH4)

51
Q

Phenylketonuria

A

Decreased phenylalanine hydroxylase or BH4 cofactor — TYROSINE BECOMES ESSENTIAL — growth retardation, seizures, fair skin, MUSTY BODY ODOR — Tx: decrease phenylalanine and increase tyrosine in diet, BH4 supplementation — autosomal recessive – avoid aspartame (contains phenylalanine) —– Maternal PKU (microcephaly and congenital heart defects in baby)

52
Q

Maple syrup urine disease

A

Blocked degradation of branched amino acids (Isoleucine, Leucine, Valine) due to decreased aKG dehydrogenase — severe CNS defects, intellectual disability, death, burnt sugar urine – autosomal recessive — Tx: restriction of branched amino acids, thiamine supplementation

53
Q

Alkaptonuria

A

Deficiency of homogenistic oxidase in degradative pathway of tyrosine to fumarate – autosomal recessive – dark connective tissue, brown pigmented sclerae, urine turns black

54
Q

Homocystinuria

A

3 types: Cystathionine synthase deficiency (tx: decrease methionine, increase cysteine, B12, and folate) — Decreased affinity of cystathionine synthase for PRP (tx: HUGELY increase B6 and increase cysteine) — Homocysteine methyltransferase deficiency (tx: increase methionine) —- All have increased homocysteine in urine, osteoporosis, intellectual disabilities, lens subluxation (down and in), marfanoid habitus, atherosclerosis, thrombosis

55
Q

Cystinuria

A

Defect of renal PCT and intestinal amino acid transporter that prevents reabsorption of COLA (Cysteine, Ornithine, Lysine, Arginine) — hexagonal cysteine stones (excessive cysteine in urine) - urinary cyanide nitroprusside test is postitive — Tx: urinary alkalinization (potassium citrate) and chelating agents (penicillamine)

56
Q

Glycogen regulation

A

Gucagon and Epinephrine increase adenylate cyclase –> cAMP –> protein kinase A –> glycogen phosphorylase kinase (also increased by calcium-calmodulin in muscle contraction) –> glycogen phosphorylase –> glucose

Insulin binds to tyrosine kinase dimer –> activates glycogen synthase and protein phosphatase –> glycogen

57
Q

Glycogen

A

Branches have a(1,6) and linkages have a(1,4) — skeletal muscle (glycogen undergoes glycogenolysis which is rapidly metabolized during exercise) — hepatocytes (glycogen is stored and udnergoes glycogenolysis to maintain blood sugar — requires debranching enzymes to get glucose off – limit dextrin refers to one of 4 resides remaining on a branch after glycogen phosphorylase

58
Q

Von Gierke disease

A

Type I glycogen storage disease (deficient glucose-6-phosphatase) - fasting hypoglycemia, LOTS of glycogen in liver, increase blood lactate, increase TGs, increase uric acid) — Tx: frequent oral glucose/cornstarch

59
Q

Glycogen storage diseases

A

Very Poor Carbohydrate Metabolism (Von Gierke, Pompe, Cori, McArdle) — all are autosomal recessive

60
Q

Pompe disease

A

Type II glycogen storage disease (lysosomal a-1,4-glucosidase deficiency) – CARDIOMEGALY, exercise intolerance

61
Q

Cori disease

A

Type III glycogen storage disease (Debranching enzyme) – normal blood lactate levels, accumulation of small dextrin like material – gluconeogenesis is intact

62
Q

McArdle disease

A

Type V glycogen storage disease (Skeletal muscle glycogen phosphorylase) – increase glycogen in muscle leading to cramps, myoglbinuria, arrhythmias — blood glucose levels unaffected – Tx: vitamin B6

63
Q

Fabry disease

A

a-galactosidase A deficiency – accumulate ceramide trihexodside – XR — severe extremity pain, decreased sweating, GI changes, angiokeratomas

64
Q

Gaucher disease

A

Glucocerebrosidase deficiency - accumulate glucocerebroside – AR – MOST COMMON! no neuro symptoms, hepatosplenomegaly, aseptic necrosis of femur, osteoporosis, Gaucher cells (crumpled tissue paper)

65
Q

Niemann Pick disease

A

Sphingomyelinase deficiency – accumulate sphingomyelin – AR – hepatosplenomegaly, cherry red spot on macula, foam cells (lipid laden macs), neurodegeneration (loss of motor skills in infant)

66
Q

Tay Sachs disease

A

Hexosaminidase A deficiency – accumulate GM2 ganglioside – AR – neurodegeneration, cherry red spot on macula, lysosomes with onion skin, NO HEPATOSPLENOMEGALY

67
Q

Krabbe disease

A

Galactocerebrosidease deficiency – accumulate galactocerebroside and psychosine – AR – peripheral neuropathy, optic atrophy, globoid cells

68
Q

Metachromatic leukodystrophy

A

Arylsulfatase A deficiency – accumulate cerebroside sulfate – central and peripheral demyelination with ataxia

69
Q

Hurler syndrome

A

a-L-iduronidase deficiency – accumulate heparan sulfate and dermatan sulfate – AR – developmental delay, airway obstruction, corneal clouding, hepatosplenomegaly

70
Q

Hunter syndrome

A

Iduronate sulfatase deficiency – accumulate heparan sulfate and dermatan sulfate – XR – mild hurler + aggressive but NO CORNEAL CLOUDING (hunters see clearly)

71
Q

Fatty acid synthesis

A

Requires transport of citrate from mitochondria to cytosol

72
Q

Long chain fatty acid degradation

A

Requires carnitine dependent transport into mitochondrial matrix — carnitine deficiency leads to toxic accumulation and hypoketotic hypoglycemia

73
Q

Medium chain acyl-CoA dehydrogenase deficiency

A

AR disorder of fatty acid oxidation — accumulation of 8-10 carbon fatty acyl carnitines in blood and hypoketotic hypoglycemia – fasting leads to hypoglycemia nd decreased ketones

74
Q

Ketone bodies

A

In alcoholism, excess NADH shunts oxaloacetate to malate — prolonged starvation and DKA leads to oxaloacetate depletion — both lead to buildup of acetyl-CoA which leads to ketone body production (can’t be used for energy in RBCs (no mitochondria) or hepatocytes (no succinyl coA-acetotate coA transferase)

75
Q

Fed state metabolism

A

Glycolysis and aerobic respiration

76
Q

Fasting state metabolism

A

Hepatic glycogenolysis, hepatic gluconeognesis, adipose relase of FFA

77
Q

Starvation 1-3 days metabolism

A

Blood glucose maintained by hepatic glycogenolysis, adipose release of FFA, muscle and liver, hepatic gluconeognesis (RBCs can’t use ketones)

78
Q

Starvation after day 3

A

Adipose stores (ketone bodies), protein degradation (organ failure and death)

79
Q

Lipid transport enzymes

A

Pancreatic lipase (degrades TGs in small intestine) — Lipoprotein lipase (degrades TGs circulating in chylomicrons and VLDLs - on vascular endothelial surface) — Hepatic TG lipase (degrades TGs remaining in IDL) — Hormone sensitive lipase (degrades TGs stored in adipocytes) — LCAT catalyzes esterification of cholesterol

80
Q

Apolipoprotein E

A

Mediates remnant uptake - all but LDL have it

81
Q

Apolipoprotein A-I

A

Activates LCAT – chylomicrons and HDL

82
Q

Apolipoprotein C-II

A

Lipoprotein lipase cofactor – chylomicrons, VLDL, HDL

83
Q

Apolipoprotein B-48

A

Mediates chylomicron secretion - chylomicrons, chylomicron remnants

84
Q

Apolipoprotein B-100

A

Binds LDL receptor - VLDL, IDL, LDL

85
Q

Chylomicron

A

Delivers dietary TGs to peripheral tissue – secreted by intestinal epithelial cells

86
Q

VLDL

A

Delivers hepatic TGs to peripheral tissue – secreted by liver

87
Q

IDL

A

Delivers TGs and cholesterol to liver

88
Q

LDL

A

Transports cholesterol from liver to tissues

89
Q

HDL

A

Transports cholesterol from periphery to liver – secreted from liver and intestine

90
Q

Familial dyslipidemias

A

1-5 in alphabetical order - C, L R, T, V — Type I (Chylomicrons - acute pancreatitis), Type II (LDL – most common, causes accelerated atherosclerosis, tendon xanthomas, and corneal arcus), Type III (Remnants - coronary artery disease), Type IV (TGs), and Type V (VLDL)

Biochem (5 decks)

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