Biochemistry Flashcards
Rate-limiting enzyme in bile acid formation?
cholesterol 7-alpha hydroxylase
2nd MC cause of enzyme deficiency-related hemolytic anemia
pyruvate kinase deficiency
progressive neurological disorder that is a result of mutations in the PDH complex
Leigh syndrome (subacute necrotizing encephalopathy)
Basic amino acids
Histidine
Lysine
Arginine
- Ornithine
- Citrulline
*not incorporated into cellular proteins bcoz there are no codons for these amino acids
an encephalopathy-psychosis syndrome due to thiamine deficiency
Wernicke-Korsakoff
MC biochemical cause of congenital lactic acidosis?
pyruvate dehydrogenase deficiency
Rate limiting step of glycolysis?
fructose 6 phosphate to fructose 1,6 bisphosphate
enzyme: phosphofructokinase (PFK 1)
drug that inhibits ATP synthase
Oligomycin
an enzyme that is inhibited by fluoroacetate (found in rat poisons)
Aconitase
citrate to isocitrate in krebs
Coenzyme of Pyruvate carboxylase
Biotin
Irreversible reactions of glycolysis
hexokinase
phosphofructokinase
pyruvate kinase
main stores of glycogen in the body
skeletal muscles
liver
Primary product if glycogenolysis
glucose 1 phosphate
Type of glycogen storage disease characterized by neutropenia and recurrent infections
Type 1b (glucose 6 phosphate translocase deficiency)
building block of glycogen
UDP glucose
Fructokinase is found in
liver
kidney
small intestine mucosa
autosomal recessive disease characterized by severe hypoglycemia, jaundice, hemorrhage, hepatomegaly, renal dysfunction, hyperuricemia and lacticacidemia due to absence of aldolase B
hereditary fructose intolerance (fructose poisoning)
Elevated galactitol can cause
cataracts
rare autosomal recessive disorder that causes galactosemia and galactosuria
Galactokinase deficiency
enzyne deficient in classic galactosemia
galactose 1 phosphate uridyltransferase (GALT)
autosomal recessive disorder that causes galactosemia, galactosuria, vomiting, diarrhea and jaundice
Classic galactosemia
- absolute contraindication to breastfeeding
Drugs that produce hemolytic anemia in pxs with G6PD?
AAA
antibiotics (sulfamethoxazole and chloramphenicol)
anti-malarials (primaquine but NOT quinine)
anti-pyretucs (acetanilud but NOT acetaminophen)
Most abundant GAGs in the body
Chrondoitin 4 and 6 sulfates
is a clinically asymptomatic genetic condition in Ashkenazi jews that involves deficiency in NADPH dependent Xylulose redutase. L-xylulose is found in significant amounts in urine.
Essential pentosuria
Beta glucuronidase deficiency
Sly syndrome (MPS III)
Enzyme deficient in Hurler syndrome
a-L-iduronidase
corneal clouding, mental retardation, dwarfism
Hurler syndrome (MPS I)
Primary target of lingual lipase
short and medium FA
Emulsification of lipids occurs in the
duodenum
An anti-obesity drug that inhibits gastric and pancreatic lipases leading to decrease fat absorption.
Orlistat
essential fatty acids
linoleic acid
a-linolenic acid
essential fatty acid deficiency can result in
ichthyosis (scaly dermatitis)
primary end product of fatty acid synthase activity
palmitate
beta oxidation of fatty occurs in the
mitochondrial matrix
a specialized carrier that transports the long chain acyl group from cytosol into the inner mitochondria
carnitine
Sources of carnitine
Diet: meat products
Synthesized from amino acids lysine and methionine by an enzymatic pathway found in the liver and kidney
Skeletal muscle: 97% carnitine
rate limiting step in F.A synthesis
carboxylation of acetyl CoA to malonyl CoA
rate limiting step in the synthesis of ketones
HMG CoA synthase
triacylglycerol synthesis occurs only in
adipose tissue
liver
lactating mammary glands
intestinal mucosal cells
major lipid component of lung surfactant
dipalmitoylphosphatidylcholine
the major structural lipid in the membranes of the nerve tissue
sphinginyelin
Niemann-Pick disease is caused by deficiency of what enzyme
Sphingomyelinase (accumulation of sphingomyelin)
Lysosomal storage disease characterized by enlarged spleen and liver.
Niemann-Pick disease (Type A)
Shell-like inclusion bodies
Tay-Sachs
rapid, progressive and fatal neurodegenerative disease associated with blindess, cherry red macula, muscular weakness and seizures.
Tay-Sachs disease
Accumulation of gangliosides (GM2)
Tay-Sachs
MC lysosomal storage disease
Gaucher disease
accumulation of glucocerebrosides characterized by hepatosplenomegaly, osteoporosis.
Gaucher disease
arylsulfatase deficiency
metachromatic leukodystrophy
condition associated with accumulation of sulfatides characterized by cognitive deterioration, demyelination, progressive paralysis and dementia.
Metachromatic leukodystrophy
beta galactosidase deficiency
Krabbe disease (Globoid cell leukodystrophy)
Globoid bodies (glycolipid-laden macrophage) in white matter of the brain is seen in what condition
Krabbe disease
Hexoaminidase A deficiency
Tay-Sachs
condition associated with deficiency of Hexoaminidase A and B ;accumulation of GM2 and globosides
Sandhoff disease
a-galactosidase deficiency
Fabry disease
condition associated with accumulation of globosides characterized by reddish-purple skin rash, kidney and heart failure and burning pain in lower extremities
Fabry disease
ceraminidase deficiency
Farber disease
accumulation of ceramide characterized by painful and progressive joint deformity, subcutaneous nodules and hoarse cry
Farber disease
Beta glucosidase deficiency
Gaucher disease
glucocerebrosidase
dietary precursor of prostaglandins
linoleic acid
2 isozymes of PGH synthase
COX 1 and 2
- COX 1- required for maintenance of healthy gastric tissue, renal homeostasis and platelet aggregation.
- COX 2 - in response to products of activated immune and inflammatory cells
rate limiting step in cholesterol synthesis
HMG-CoA reductase ( reduction of HMG-CoA to mevalonate)
autosomal recessive disorder caused by partial deficiency in 7-dehydrocholesterol-7-reductase (DHCR7)
Smith Lemi Opitz Syndrome (SLOS)
impaired cholesterol synthesis (DHCR7 is required for the reduction of 7-dehydrodesmosterol to desmosterol
characterized by microcephaly, bitemporal narrowing, capillary hemangioma of the nose
Primary bile acids
Cholic acid
Chenodeoycholic acid
rate limiting step in bile acid synthesis
introduction of hydroxyl group at carbon 7 of the steroid nucleus by cholesterol-7-a-hydroxylase
is a rare hypolipoproteinemia caused by defect in microsomal triacylglyerol caused by defect in MTP. As a consequence, no VLDL or chylomicrons are formed.
Abetalipoproteinemia
autosomal recessive cause by deficienies in the ability to hydrolyze lysosomal cholesteryl esters
Wolman disease
deficiency of ABCA1, characterized by the virtual absence of HDL particles due to degradation of lipid poor apo A-1
Tangier disease
rate limiting reaction of steroid hormone synthesis
conversion of cholesterol to the 21-carbon pregnenolone (desmolase)
MC form of Congenital Adrenal Hyperplasia
21-a-hydroxylase deficiency
autosomal recessive characterized by no glucoorticoids, no mineralocorticoids and no androgens
3-B-hydroxysteroid dehydrogenase deficiency
Parent compound for all steroid hormones
Pregnenolone
zones of the adrenal cortex and their corresponding hormones
zona glomerulosa - mineralocorticoid (aldosterone)
zona fasciculata - glucocorticoid (cortisol)
zona reticularis - sex hormones
hormone that induces testosterone synthesis in the Leydig cells, induces ovulation and stimulates estrogen & progesterone synthesis in the corpus luteum
Luteinizing hormone
is a disease of malabsorption resulting from immune-mediated damage to the small intestine in response to ingestion of gluten (or gliadin from gluten), a protein found in wheat, barley and rye.
Celiac sprue
Drug used to treat pxs with urea cycle defects
Phenylbutyrate
- prodrug that is rapidly converted to phenylacetate, which combines with glutamine to form phenylglutamine.
- phenylglutamine containing two atoms of nitrogen, is excreted in the urine, thus assisting clearance of nitrogenous waste
MC cause of congential hyperammonemia
OTC deficiency (X-linked)
Essential amino acids
1. Glucogenic histidine methionine threonine valine
- Ketogenic
leucine
lysine - glucogenic & ketogenic
isoleucine
phenylalanine
tryptophan
Amino acid that form Oxaloacetate
Asparagine
enzyme that is used to treat leukemia. It deprives the cancer cells of its required nutrient.
Asparaginase
- rapidly dividing leukemic cells are unable to synthesize sufficient asparagine to support their growth therefore require asparagine from blood.
- Asparaginase lowers the level of asparagine
amino acids that form a-ketoglutarate
glutamine
proline
arginine
histidine
amino acids that form pyruvate
alanine serine glycine cystine threonine
amino acids that form fumarate
phenylalanine
tyrosine
amino acid that forms succinyl CoA
methionine
valine
isoleucine
threonine
3 vitamins involved in the conversion of homocysteine to methionine or cysteine
folate
B12
B6
Branched-chain amino acids
Leucine
Isoleucine
Valine
amino acids that form acetyl CoA
Leucine
Isoleucine
Lysine
Tryptophan
MC genetic error of amino acid transport
Cystinuria
disease due to a deficiency in fumaryl-acetoacetate hydrolase; accumulation of fumarylqcetoacetate; cabbage like odor in urine
Tyrosinemia type 1
this disease is due to a deficiency in branched-chain a-keto acid dehydrogenase; elevated branched chain amino acids
Maple syrup urine disease
this disease is due to a deficiency in methylmalonyl CoA mutase; elevated levels of methylmalonic acid in blood
Methylmalonate CoA mutase deficiency
this disease is due to a deficiency in histidase
Histidemia
characterized by accumulation of cystathionine due to a deficiency in cystathionase
Cystthioninuria
due to a deficiency in cystathionine synthase; accumulation of homocysteine
-MR, osteoporosis, M.I, dislocation of lens
Homocystinuria
caused by a deficiency of phenyalanine hydroxylase
PKU
MC cause of homocystinuria
defect in the enzyme cystathionine B-synthase
disease due to a deficiency of homogenistic acid oxidase characterized by black urine, large joint arthritis, black pigments on cartilage
Alkaptonuria
what enzyme is deficient in homocystinuria, methylmalonic acidemia, MSUD, oculocutaneous albinism, PKU
cystathionine B synthase methylmalonic CoA mutase branched chain a keto dehydrogenase tyrosinase phenylalanine hydroxylase
major sites of heme synthesis
liver
erythrocyte producing cells of the bone marrow
rate limiting step in porphyrin biosynthesis
formation of ALA (ALA synthase)
MC porphyria
Porphyria cutanea tarda
disease associated with deficiency in uroporphyrinogen decarboxylase
Porphyria cutanea tarda
ALA dehydratase deficiency characterized by acute attacks of gastrointestinal, neuropsychiatric, motor symptoms and photosensitivity
Acute hepatic porphyria
characterized by skin rashes and blisters in early childhood. complicated by cholestatic liver disease
erythropoietic porphyria
an acute disease caused by a deficiency in hydroxymethylbilane synthase.
acute intermittent porphyria
not photosensitive
disease is caused by a deficiency in ferrochelatase leading to protoporphyrin accumulation
erythropoietic protoporphyria
acute disease caused by a deficiency in protoporphyrinogen oxidase
variegate protoporphyria
acute diseasae caused by a deficiency in corproporphyrinogen oxidase
hereditary coproporphyria
normal production of bilirubin
300 mg/day
the parent purine nucleotide
inosine monophosphate
X-linked recessive inherited disorder associated with deficiency of hypoxanthineguanine phosphoribosyl transferase (HGPRT) characterized by excessive uric acid production, self mutilation and involuntary movements
Lesch Nyhan syndrome
end product of purine degradation
uric acid
definitive diagnosis of gout
aspiration of synovial fluid from an affected joint using a polarized light microscopy to confirm the presence of needle shaped monosodium urate crystals
this disorder is characterized by hyperuricemia with recurrent attacks of acute arthritic joint inflammation caused by deposition of monosodium urate crystals
gout
-hyperuricemia results in underexcretion of uric acid
drug that inhibits xanthine oxidase
allopurinol (in the body converted to oxypurinol)
- resulting in accumulation of hypoxanthine and xanthine (more soluble compounds)
- for overproducers of uric acid
autosomal recessive deficiency causes a type of severe combined immunodefiency involving lymphocytopenia
adenosine deaminase deficiency
- lymphocytes have the highest activity of ADA
- accumulation of adenosine which is converted to ribonucleotide or deoxyribonucleotide by cellular kinases
- elevate dATP results in inhibition of ribonucleotid reductase
- thus preventing production of all deoxyribose containing nucleotides
- developmentak arrest and apoptosis of lymphocytes
autosomal recessive, less severe Immunodeficiency disease involving T cells characterized by recurrent infections and neurodedvelopmental delay
purine nucleoside phosphorlase (PNP) deficiency
drug that prevents formation of microtubules thus decreasing the movement of neutrophils into the affected area
colchicine
-no effect on uric acid levels
drugs that increase renal excretion of uric acid
uricosuric agents (probenecid or sulfinpyrazone) - for underexcretors of uric acid
non-purine inhibitor of xanthine oxidase
febuxostat
oral hypoglycemic agent that increases insulin secretion by closing ATP sensitive potassium channels
sulfonyureas
the counter regulatory hormones
glucagon
epinephrine
cortisol
growth hormone
Treatment for insulin induced hypoglycemia in conscious and unconscious pxs
oral CHO
SC or IM glucagon
Folic acid deficiency will lead to
megaloblastic anemia
neural tube defects
Cobalamin (vit B12) deficiency
penicious anemia
dementia
spinal degeneration
Vitamin C deficiency
scurvy
Niacin (Vitamin B3) deficiency
Pelagra (dementia, dermatitis, diarrhea)
thiamine (Vit B1) deficiency
beriberi
wernicke-korsakoff syndrome
Other names of the fat soluble vitamins
A - retinol, retinoic acid, retinal, B carotene
D - cholecalciferol, ergocalciferol
E- a tocopherol
K - menadione, menaquinone, phylloquinone
Vitamin A deficiency
night blindess, infertility
Vitamin D deficiency
rickets in children
osteomalacia in adults
Vitamin K deficiency
bleeding
Saturated fatty acids
Myristic
Palmitate
Stearic -little effect on blood cholesterol
define as the negative log of the hydrogen ion concentration
pH
normal pH of blood
7.35 - 7.45
Nicotinamide adenine dinucleotide (NAD) is derived from?
vitamin B3 - niacin
Inhibitors of complex IV (cytochrom oxidase)
cyanide
carbon monoxide
sodium azide
hydrogen sulfide
inhibitors of complex I (NADG dehydrogenase)
barbiturates
amytal
rotenon
piericidin A
inhibitors of complex II (succinate dehydrogenase)
malonate
carboxin
TTFA (thenoyltrifluoroacetone)
inhibitors of complex ||| (ubiquinol ferrocytochrome oxireductase
antimycin A
dimercaprol
Example of uncouplers
2,4 dinitriphenol
aspirin
thermogenin
brown fat
hyperpyrexia related to aspirin overdose is due to
aspirin uncoupling
Other name of complex V
ATP synthase
are unstable products that are formed as a by product of ETC when molecular oxygen is partially reduced
reactive oxygen species (superoxide, hydrogen peroxide, hydroxyl radical)
Defenses against ROS accumulation
Superoxide dismutase
catalase
glutathione peroxidase
mitochondria disease involving all complexes
fatal infantile mitochondrial myopathy
mitochondrial disease involving complex 1
MELAS
mitochondrial encephalomyopathy, lactic acidosis, stroke like episodes
- one of the reasons for stroke in the young
single most common sign of mitochondrial myopathy
chronic progressive external opthalmoplegia
mitochondrial disease involving complex II with a define triad of clinical findings before age 20, CPEO and pigmentary retinopathy
Kearns sayre syndrome (KSS)
- cardinal sign: DM
- cause of death: heart block
- MC caus is a deletion of 4,977 bp contiguous of mtDNA
Harrisons pg. 3503
MC mitochondrial encephalomyopathy
MELAS
- 1st sign: seizure
occur before age 20
cause by point mutation of mtRNA
myoclonic epilepsy, cerebellar ataxia, progressive muscle weakness
Myoclonic epilepsy with ragged red fibers
MC cause of recurrent myoglobinuria
Carnitine palmitoyltransferase (CPT II) deficiency - early twenties, muscle pain, myoglobinuria after long exercise
seizure disorder associated with MR
phosphofglycerate kinase deficiency
disorders of glycolysis
slowly, progressive form of muscle weakness that develops after puberty. usually diagnosed in infancy bcoz of hypotonia, delayed motor milestones and growth retardation
debranching enzyme deficiency (type 3 glycogenosis)
prominent contracturew, muscle weakness, cardiomyopathy
Emery dreifuss muscular dystrophy
- caused by emerin mutations
X linked
glucose + glucose
maltose
disaccharide found in fungi and yeasts
trehalose
polysaccharide of fructose used to determine GFR
inulin
compounds that have same chemical formula but different structures
isomers
compounds that differ in configuration around only one specific carbon atom with exception of the carbonyl carbon
epimers
pairs of structures that are mirror images of each other
enantiomers
sugars are convertible between a linear or cyclic form
anomners
MC is cyclic or ring form (haworth projection)
linear is fischer
principal sites of CH2OH digestion
mouth
intestinal lumen
carbohydrate digestion begings during
mastication (salivary amylase)
major pathway of glucose metabolism that converts glucose into 3 carbon compounds to provide energy
glycolysis
- occurs in the cytoplasm
- substrate is glucose
- end product are pyruvate (aerobic) or lactate (anaerobic)
ATP production in glycolysis occurs in
- 1,3 bisphosphoglycerate to 3, phosphoglycerate (phosphoglycerate kinase)
- PEP to pyruvate (pyruvate kinase)
chemical that inhibits pyruvate dehydrogenase by binding to lipoic acid
arsenic
MC enzyme defect in glycolysis
pyruvate kinase deficiency
an x linked dominant condition and is the most common cause of congenital lactic acidosis
pyruvate dehydrogenase deficiency
it is the final common pathway for the aerobic oxidation of all nutrients
TCA
substrate: acetyl CoA
products: CO2, GTP, NADH, FADH2
rate limiting step of TCA
isocitrate to a ketoglutarate
enzyme: isocitrate dehydrogenase
NADH production in TCA occurs in
- isocitrate to a ketoglutarate (isocitrate dehydrogenase)
- a ketoglutarate to succinyl CoA (a ketoglutarate dehydrogenase)
- malate to OAA (malate dehydrogenase)
GTP production on TCA occurs in
succinyl CoA to succinate (succinate thiokinase)
FADH2 in TCA occurs in
succinate to fumarate (succinate dehydrogenase)
CO2 production in krebs occurs in
isocitrate to aketoglutarate
aketoglutarate to succinyl CoA
ATP yield for TCA
12 ATP from acetyl CoA
15 ATP from pyruvate
NADH 3x3 = 9
FADH 1 x 2 = 2
GTP = 1
intermediates of TCA
citrate: delivers acetyl CoA to the cytoplasm for F.A synthesis via citrate shuttle
succinyl CoA: heme synthesis and activation of ketone bodies
malate: gluconeogensis
rate limiting step of gluconeogenesis
fructose 1,6 bisphosphate to fructose 6 phosphate
enzyme: fructose 1,6 bisphosphatase
gluconeogenesis occurs in
liver 90%
kidney 10%
both cytoplasm and mitochondrial
substrate: pyruvate
product: glucose
step in gluconeogenesis that requires biotin
pyruvate to OAA (pyruvate carboxylase)
all carboxylases require ______ cofactor
biotin
pyruvate carboxylase
acetyl CoA carboxylase
propionyl CoA carboxylase
rate limiting step of glycogenesis
elongation of glycogen; addition of a (1,4) bonds
glycogen synthase
rate limiting step of glycogenolysis
removal of glucose (break a 1,4 bonds)
glycogen phosphorylase
benign condition characterized by appearance of fructose in blood and urine due to defect in fructokinase
essential fructosuria
substrate for pentose phosphat pathway
glucose 6 phosphat
products for pentose phosphate pathway
ribose 5 phosphate
glyceraldehyde 3 phosphate
NADPH
rate limiting step of Pentose phosphate pathway
glucose 6 phosphate to 6 phosphogluconate
glucose 6 p dehydrogenase
used to diagnose thiamine deficiency
rbc transketokase activity
MC common disease producing enzyme abnormality in humans
glucose 6 phosphate dehydrogenase deficiency