Biochemistry- First Aid

Question 1

Amino Acids necessary for purine synthesis

Answer 1

Glycine, Aspartate, Glutamine

Question 2

Drugs that interfere with de novo pyrimidine and purine synthesis

Answer 2

Leflunomide, Mycophenolate, ribavirin, hydroxyurea, 6-mercaptopurine, azathiopirine, 5-fluorouracil, methotrextate, trimethoprim, pyrimethamine
FA P. 67

Question 3

Adenosine deaminase

Answer 3

Converts Adenosine–> Inosine

Deficiency leads to decreased DNA synthesis and decreased lymphocyte count (cause of AR SCID)

Question 4

Lesch-Nyhan syndrome (loss of HGPRT, x-linked)

Answer 4

HGPRT converts guanine–> GMP and hypoxanthine–> IMP
Results in excess uric acid production and de novo purine synthesis
Findings: intellectual disability, self-mutilation, aggression, hyperuricemia, gout, dystonia

Question 5

RNA polymerase types in the eukaryote

Answer 5

I- makes rRNA
II- makes mRNA
III- makes tRNA
Note- 1 RNA polymerase makes all 3 kinds of RNA in prokaryotes

Question 6

RNA processing in eukaryotes

Answer 6

Capping of the 5’ end with 7-methylguanosine cap
Polyadenylation of 3’ end
Splicing out of introns

Question 7

Regulators of the cell cycle

Answer 7

Cyclin-CDK complexes
Tumor supressors (p53 and hypophosphorylated Rb inhibit G1 to S progression)

Question 8

Inclusion Cell Disease

Answer 8

Defect in phosphotransferase which phosphorylates mannose residues on glycoproteins destined for the lysosome
Findings: coarse facial features, clouded corneas, restricted joint movement, high plasma levels of lysosomal enzymes

Question 9

Drugs that act on microtubules

Answer 9

Mebendazole (anti-helminthic), Griseofulvin (anti-fungal), Colchicine (anti-gout), Vincristine (anti-cancer), Paclitaxel (anti-cancer)

Question 10

Collagen Types

Answer 10

I- most common, found in bone, skin, tendon, fascia, cornea, and late wound repair
II- cartilage, vitreous body, nucleus pulposus
III- reticulin, blood vessels
IV- basement membrane, basal lamina lens

Question 11

Marfan syndrome (cause)

Answer 11

Defect in fibrillin (fibrillin-1), a glycoprotein scaffold for elastin

Question 12

Emphysema (cause)

Answer 12

Loss of alpha-1-antitrypsin, an inhibitor of elastase activity

Question 13

Trinucleotide repeat diseases

Answer 13

Fragile X- CGG
Friedreich ataxia- GAA
Huntington’s- GAG
Myotonic dystrophy- CTG

Question 14

Findings of Down syndrome (trisomy 21)

Answer 14

ID, flat facies, prominent epicanthal folds, single palmar crease, gap between 1st 2 toes, duodenal atresia, Hirschsprung disease, congenital heart disease, ASD

Question 15

Findings of Edwards syndrome (trisomy 18)

Answer 15

severe ID, rocker-bottom feat, micrognathia, low-set ears, clenched hands, prominent occiput, congenital heart disease

Question 16

Findings of Patau syndrome (trisomy 13)

Answer 16

severe ID, rocker bottom feat, microphthalmia, microcephaly, cleft lip/palate, holoprosencephaly, polydactyly, congenital heart disease

Question 17

Cri-du-chat syndrome

Answer 17

Congenital microdeletion of short arm of chromosome 5

Microcephaly, moderate to severe intellectual disability, high pitched crying, epicanthal folds, VSD

Question 18

Williams syndrome

Answer 18

Congenital microdeletion of long arm of chromosome 7
Distinctive “elfin” facies, ID, hypercalcemia, well-developed verbal skills, extreme friendliness with strangers, cardiovascular problems

Question 19

22q11 microdeletion

Answer 19

DiGeorge syndrome- thymic aplasia, parathyroid aplasia, cardiac defects
Velocardiofacial syndrome- cleft palate, abnormal facies, cardiac defects

Question 20

TCA Cycle

Answer 20

citrate–> isocitrate–> alpha-ketoglutarate–> succinyl coA–> succinate–> fumarate–> malate–> oxaloacetate

Question 21

Urea Cycle

Answer 21

ornithine + carbamoyl phosphate–> citrulline–> arginosuccinate–> arginine

Question 22

Uses of NADPH (electron acceptor)

Answer 22

Steroid and fatty acid synthesis, respiratory burst, cytochrome P-450, glutathione reductase

Question 23

Regulation of Pyruvate Dehydrogenase

Answer 23

ATP, Acetyl-CoA, NADH (-)

Question 24

Citrate synthase

Answer 24

APT (-)

Question 25

Isocitrate Dehydrogenase

Answer 25

ATP, NADH (-), ADP (+)

Question 26

Alpha-KG dehydrogenase

Answer 26

Succinyl-CoA, NADH, ATP (-)

Question 27

Electron transport inhibitors

Answer 27

Decrease proton gradient and block ATP synthesis

Ex. Rotenone, cyanide, antimycin A, CO

Question 28

ATP synthase inhibitors

Answer 28

Directly inhibit mitochondrial ATP synthase, causing an increased proton gradient but not ATP snythesis
Ex. Oligomycin

Question 29

Uncoupling agents

Answer 29

Increase permeability of membrane causing decreased proton gradient and increased consumption of O2, ATP synthesis stops but electron transport continues, generating heat
Ex. 2,4 Dinitrophenol, aspirin

Question 30

Cause of essential fructosuria

Answer 30

defect in fructokinase

Question 31

Cause of fructose intolerance

Answer 31

deficiency in aldolase B

Question 32

Galactokinase deficiency

Answer 32

AR hereditary deficiency in galactokinase

Question 33

Classic galactosemia

Answer 33

absence of galactose-1-phosphate uridyltransferase

Question 34

Essential Amino Acids

Answer 34

Methionine, Valine, Histidine, Isoleucine, Phenylalanine, Threonine, Tryptophan, Leucine, Lysine

Question 35

Phenylketonuria (AR deficiency in phenylalanine hydroxylase) findings

Answer 35

ID, growth retardation, seizures, fair ski, eczema, musty body odor

Question 36

Alkaptonuria (cause)

Answer 36

congenital deficiency of homogentisate oxidase (homogentisic acid–> maleylacetoacetic acid, tyrosine–> fumarate)

Question 37

Alkaptonuria (findings)

Answer 37

dark connective tissue, brown pigmented sclerae, urine turns black on prolonged exposure to air, arthralgias (homogentisic acid is toxic to cartilage)

Question 38

Homocystinuria (findings)

Answer 38

increased homocysteine in urine, ID, osteoporosis, tall stature, kyposis, lens subluxation, thrombosis, atherosclerosis (stroke and MI)

Question 39

Fabry disease (deficient enzyme, accumulated substrate, findings)

Answer 39

alpha-galactosidase A; ceramide trihexose; peripheral neuropathy of hands/feet, angiokeratomas, cardiovascular/renal disease

Question 40

Gaucher disease (deficient enzyme, accumulated substrate, findings)

Answer 40

glucocerebrosidase; glucocerebroside; hepatosplenomegaly, pancytopenia, aspetic necorsis of femur, bone crises, Gaucher cells

Question 41

Niemann-Pick disease (deficient enzyme, accumulated substrate, findings)

Answer 41

sphingomyelinase; sphingomyelin; progressive neurodegeneration, hepatosplenomegaly, cherry red spot on macula, foam cells

Question 42

Tay-Sachs disease (deficient enzyme, accumulated substrate, findings)

Answer 42

hexosaminidase A; GM2 ganglioside; progressive neurodegeneration, developemental delay, cherry-red spot on macula, lysosomes with onion skin, no hepatosplenomegaly

Question 43

Krabbe disease (deficient enzyme, accumulated substrate, findings)

Answer 43

Galactocerebrosidase; galactocerebroside; peripheral neuropathy, developemental delay, optic atrophy, globoid cells

Question 44

Metachromatic leukodystrophy (deficient enzyme, accumulated substrate, findings)

Answer 44

arylsufatase A; cerebroside sulfate; central and peripheral demyelination with ataxia, dementia

Question 45

Hurler syndrome

Answer 45

alpha-L-iduronidase; heparan sulfate; developemental delay, gargoylism, airway obstruction, corneal clouding, hepatosplenomegaly

Question 46

Hunter syndrome

Answer 46

iduronate sulfatase; heparan sulfate; mild hurler with agressive behavior, no corneal clouding

Question 47

Pyocyanin

Answer 47

Produced by P. aeruginosa, functions to generate ROS to kill competing microbes

Question 48

Lactoferrin

Answer 48

protein found in secretory fluids and neutrophils that inhibits microbial growth via iron chelation