Biochemistry Flashcards
Vitamin A
Retinol
Fxn: antioxidant, visual pigment (retinal)
Def: night blindness, dry/scaly skin, alopecia, immune sup
Excess: arthralgia, scaly skin, alopecia, increased intracranial P, teratogenic (cleft palate/cardiac abn)
Vitamin B1
Thiamine
Fxn: TPP in dehydrogenase rxns
Def: impaired glucose breakdown –> ATP depletion in highly aerobic tissues (brain/heart)
Wernicke-Korsakoff & Beriberi
Vitamin B2
Riboflavin
Fxn: FAD/FMN in redox rxns, each generate 2 ATPs
Def: cheilosis, corneal vascularization
Vitamin B3
Niacin
Fxn: NAD/NADP in redox rxns, each generate 3 ATPs; syn w/ Trp & requires B2 & B6
Def: Pellagra (diarrhea, dementia, dermatitis)
Excess: flushing (via PG), hyperglycemia, hyperuricemia
Vitamin B5
Pantothenate
Fxn: CoA & fatty acid synthase component
Def: dermatitis, enteritis, alopecia, adrenal insuff
Vitamin B6 (Pyridoxine)
Fxn: PLP in transamination/decarboxylation rxns; in syn of cystathonine/heme/niacin/histamine/NTs
Def: convulsions, hyperirritability, peripheral neuropathy, sideroblastic anemia
Vitamin B7
Biotin
Fxn: carboxylation cofactor
Def: w/ raw egg whites or abx –> dermatitis, alopecia, enteritis
Vitamin B9
Folic acid
Fxn: converted to THF –> methylation rxns
Def: megaloblastic anemia/hypersegmented PMNs, glossitis; increased homocysteine
Cause: phenytoin/sulfonamides/MTX
Vitamin B12
Cobalamin
Rxn: homocysteine methyltransferase & methylmalonyl-CoA mutase cofactor
Def: megaloblastic anemia/hypersegmented PMNs; parasthesias/subacute combined degeneration; increased homocysteine & MMA
Vitamin C
ascorbic acid
Fxn: facilitates Fe abs (via reduction), collagen hydroxylation, DA hydroxylation –> NE
Def: swollen gums/bruising/hemarthrosis/anemia/poor wounf healing
Excess: N/V, diarrhea, CaOxalate kidney stone
Vitamin D
Def: rickets (child, deformed), osteomalacia (adults, weak), tetany
Excesss: appetite loss, stupor
Vitamin E
Fxn: protect membranes from FR damage & enhance warfarin anticoag effects
Def: hemolytic anemia, acanthocytosis, neuro sx’s like B12 def but w/o megaloblastic anemia/hypersegmented PMNs
Vitamin K
Synthesize by intestinal flora
Def: in neonatal hemorrhage (can’t syn vit K in colon), or prolonged abx use
Zinc
Def: delayed wound healing, hypogonadism, decreased adult hair, dysgeusia/anosmia
Glycolysis
rate determining enzyme
Phosphofructokinase-1 (PFK-1)
+ = AMP, F2,6BP
- = ATP, citrate
Gluconeogenesis
rate determining enzyme
Fructose-1,6-bisphosphonate
+ = ATP, acetyl-CoA
- = AMP, F2,6BP
TCA cycle
rate determining enzyme
Isocitrate dehydrogenase
+ = ADP
- = ATP, NADH
Glycogenesis
rate determining enzyme
Glycogen synthase
+ = G6P, insulin, cortisol
- = Epi, glucagon
Glycogenolysis
rate determining enzyme
Glycogen phosphorylase
+ = Epi, glucagon, AMP
- = G6P, insulin, ATP
HMP shunt
rate determining enzyme
G6PD
+ = NADP+
- = NADPH
De novo pyrimidine synthesis
rate determining enzyme
Carbamoyl phosphate synthase II
De novo purine synthesis
rate determining enzyme
Glutamine-phosphoribosylpyrophosphate (PRPP) amidotransferase
- = AMP, IMP, GMP
Urea cycle
rate determining enzyme
Carbamoyl phosphate synthase I
+ = N-acetylglutamate (cofactor)
Fatty acid synthesis
rate determining enzyme
Acetyl-CoA carboxylase (ACC)
+ = insulin, citrate
- = glucagon, palmitoyl-CoA
Fatty acid oxidation
rate determining enzyme
Carnitine acyltransferase I
- = malonyl-CoA
Ketogenesis
rate determining enzyme
HMG-CoA synthase
Cholesterol synthesis
rate determining enzyme
HMG-CoA reductase
+ = insulin, thyroxine
- = glucagon, cholesterol
Pyruvate dehydrogenase complex deficiency
pyruvate buildup –> increased lactate & alanine
Tx: ketogenic nutrients (acetyl-CoA bypass PDH complex)
Essential fructosuria
Def: Fructokinase
increased fructose in blood/urine
Fructose intolerance
Def: Aldolase B
fructose-1-P accumulates & decrease free P –> inhibit glycogenolysis/gluconeogenesis –> hypoglycemia after fructose/sucrose ingestion
P/w: jaundice, cirrhosis, vomiting
Galactokinase deficiency
Def: Galactokinase
some galactitol accumulation
P/w: infantile cataracts
Classic galactosemia
Def: Galactose-1-P urisyltransferase Def
galactose-1-P & galactitol accumulation
P/w: FTT, jaundice, hepatomegaly, infantile cataracts, MR
Essential AAs
Glucogenic: Met, Val, His
Glucogenic/Ketogenic: Ile, Phe, Thr, Trp
Ketogenic: Leu, Lys
N-acetylglutamate deficiency
hyperammonemia
identical presentation as CPS-I deficiency
Ornithine transcarbamylase deficiency
X-linked recessive
hyperammonemia, increased orotic acid, decreased BUN
NO megaloblastic anemia (vs orotic acidemia)
Phenylketonuria
Def: Phenylalanine hydroxylase OR tetrahydrobiopterin cofactor
P/w: mental/growth retardation, seizures, fair skin, eczema, musty/mousy body odor
Alkaptonuria
Def: Homogentisate oxidase Def
homogentisic acid accumulation (pathway from tyr to fumarate)
P/w: dark CT, brown sclerae, black urine, arthralgia
Homocystinuria
- Cystathione synthase Def OR decreased affinity for B6 = increased homocysteine/methionine; decreased cysteine
- Homocysteine methyltransferase Def = increased homocysteine/cysteine; decreased methionine
P/w: MR, tall, kyphosis, lens down/in, thrombosis/atherosclerosis
Cystinuria
Def: renal PCR/intestinal AA transporter
Cysteine/Ornithine/Lysine/Arginine excess in urine
Maple syrup urine disease
Def: alpha-ketoacid dehydrogenase (B1)
increased alpha-ketoacid in blood
Von Gierke disease (type I)
Def: Glucose-6-phosphatase (LIVER)
P/w: increased glycogen in liver (hepatomegaly), severe fasting hypoglycemia, increased blood lactate (d/t glucose not able to leave liver to other cells)
Pompe disease (type II)
Def: Lysosomal alpha-1,4-glucosidase (acid maltase) (HEART)
P/w: cardiomyopathy (d/t glycogen accumulation in lysosome)
Cori disease (type III)
Def: Debranching enzyme (alpha-1,6-glucosidase) (LIVER)
P/w: mild disease
McArdle disease (type V)
Def: Skeletal muscle glycogen phosphorylase (myophosphorylase)
P/w: increased glycogen in muscle –> painful muscle cramps/myoglobinuria
Fabry disease
Def: alpha-galactosidase A (X-linked recessive)
Subs: Ceramide trihexoside
P/w: peripheral neuropathy, angiokeratomas, CV/renal disease
Gaucher disease
Def: Glucocerebrosidase (beta-glucosidase) MC
Subs: Glucocerebroside
P/w: hepatosplenomegaly, pancytopenia, lipid-laden macrophages, NO neuro involvement
Niemann-Pick disease
Def: Sphingomyelinase
Subs: Sphingomyelin
P/w: neurodegeneration, hepatosplenomegaly, cherry-red macula spot, lipid-laden macrophages
Tay-Sachs disease
Def: Hexosaminidase A
Subs: GM2 ganglioside
P/w: neurodegeneration, cherry-red macula spot, onion skin lysosomes
Krabbe disease
Def: Galactocerebrosidase
Subs: Galactocerebroside, psychosine
P/w: peripheral neuropathy, dev’t delay, optic atrophy, globoid cell
Metachromatic leukodystrophy
Def: Arylsulfatase A
Subs: Cerebroside sulfate
P/w: central/peripheral demyelination w/ ataxia, dementia
Hurler Syndrome
Def: alpha-L-iduronidase
Subs: heparan sulfate, dermatan sulfate
P/w: dev’t delay, gargoylism, airway obstruction, corneal clouding, hepatosplenomegaly
Hunter Syndrome
Def: Iduronate sulfatase (X-linked recessive)
Subs: heparan sulfate, dermatan sulfate
P/w: mild Hurler + aggressive behavior, NO corneal clouding
Carnitine deficiency
No LCFA transport into mitochondria –> weakness, hypotonia, hypoketotic hypoglycemia
Acyl-CoA dehydrogenase deficiency
no acetyl-CoA from oxidation of FAs –> decreased pyruvate carboxylase activity (acetyl-CoA = + regulator) –> decreased fasting glucose
Apoplipoprotein E
mediates remnant uptake
Apoplipoprotein A-I
activates LCAT –> C to CE –> drives CE into HDL
Apoplipoprotein C-II
LPL cofactor
Apolipoprotein B-48
mediates CM secretion (intestinal cells)
Apolipoprotein B-100
binds LDL R –> mediates uptake of VLDL/IDL/LDL
