Biochemistry Flashcards
Metalloproteinase
breakdown collagen for remodeling (ie destabilize arterial plaques)
Prolyl hydroxylase
hydroxylation of proline on pro collagen to form a stable collagen triple helix (stabilizes collagen)
Lysyl oxidase
strengthens collagen fibers by converting lysine to aldehyde (stabilizes collagen)
Procollagen peptidase
cleaves the terminal ends of pro collagen molecules to form insoluble tropocollagen that will aggregate to form collagen fibrils
Ehlers-Danlos pts have a deficiency of what enzyme
Procollagen peptidase –> disorganized collagen bundles
Tetrahydrobiopterin
cofactor in the synthesis of DA, 5-HT, & Tyrosine (DA & melanin precursor)
Nucleosome
core of histones (H2A, H2B, H3, H4) + DNA
Histones are composed of what a.a.?
Arginine & lysine === positive-charge
DNA is negatively charges d/t
phosphates
Linker histone
H1
Deamination of cytosine
uracil
Which nucleotides raise the melting temp of DNA?
Cytosine & Guanine rich DNA (3H bonds)
Which a.a. are necessary to make purines?
glycine, glutamine, & aspartate
What 5 substances are needed to make a purine?
glycine, glutamine, & aspartate + tetrahydrofolate & CO2
Which a.a. are necessary to make pyrimidines?
aspartate & glutamine
What 4 substances are needed to make a pyrimidines?
aspartate, CO2, glutamine, ATP
Carbamoyl phosphate
necessary for pyrimidine synthesis, composed from CO2, glutamine, & ATP
Rate-limiting step for pyrimidine synthesis
Carbamoyl phosphate synthetase-2 (CPS-2)
CPS-2
Pyrimidine synthesis, found in cytosol, Nitrogen source is Glutamine
CPS-1
Urea cycle, found in mitochondria, Nitrogen source is Ammonia
CPS-2 catalyzes
CO2+ glutamine + ATP –> Carbamoyl phosphate
Orotic aciduria disease: deficiency in
UMP synthase
Ribonucleotide reductase catalyzes
UDP –> dUDP (pyridine synthesis)
What drug inhibits Ribonucleotide reductase?
Hydroxyurea
Hydroxyurea is used to treat
Sickle Cell
Chemotherapeutic (CML, melanoma)
Thymidylate synthase catalyzes
dUMP –> dTMP (pyridine synthesis)
Tetrahydrofolate is used in this step
Dihydrofolate reductase catalyzes
dihydrofolate —> tetrahydrofolate for the conversion of dUMP -> dTMP
Which drug inhibits Thymidylate synthase?
5-Flourouracil (uracil analog)
5-Flourouracil is used to treat?
Chemotherapeutic agent (adenocarcinoma, colon)
Which drug inhibits Dihydrofolate reductase?
Methotrexate & Trimethoprim (prokaryotes)
Orotic aciduria
AR disease that causes orotic aciduria + megaloblastic anemia (cannot synthesize pyrimidines)
Ornithine Transcarbamylase Deficiency
orotic aciduria + hyperammonemia
Tx of orotic aciduria?
Uridine supplement
Rate-limiting step of Puridine synthesis?
Glutamine PRPP Amidotransferase (PRPP -> IMP)
Which drug inhibits Glutamine PRPP Amidotransferase?
6-Mercaptopurine, Azathioprine (6-MP analog)
IMP dehydrogenase catalyzes
IMP —> GMP
Which drug inhibits IMP dehydrogenase?
Mycophenolate
Xanthine Oxidase catalyzes
Hypoxanthine –> xanthine
xanthine –> uric acid (purine degradation)
Which drug inhibits Xanthine oxidase?
Allopurinol
Allopurinol will increase the serum concentration of which drugs?
6-Mercaptopurine & Azathioprine
HGPRT catalyzes
Guanine &/or Hypoxanthine –> GMP &/or IMP (Purine salvage)
Lesch-Nyhan Syndrome - deficiency of
HGPRT enzyme (inability to salvage purines)
Lesch-Nyhan Syndrome Sx
gout, aggressive behavior, low IQ, self-mutilation (lip biting), movement disorder
Tx for Lesch-Nyhan Syndrome
Tx gout w/ Allopurinol or Febuxostate
Genetics of Lesch-Nyhan Syndrome
X-linked
SCID is most frequently caused by a deficiency in
Adenosine Deaminase
Adenosine deaminase catalyzes
adenosine –> inosine (purine degradation)
Rate-limiting step in purine synthesis?
Glutamine PRPP Amidotransferase
Rate-limiting step in pyrimidine synthesis?
CPS-2
The carbon source in purine synthesis comes from?
CO2, Glycine, Tetrahydrofolate
The carbon source in pyrimidine synthesis comes from?
Aspartate, CO2
Hydroxyurea
ribonucleotide reductase inhibitor
Methotrexate & Trimethoprim
Dihydrofolate reductase inhibitor
5-FU
Thymidylate synthase inhibitor
Mycophenolate
IMP dehydrogenase inhibitor
6-MP
PRPP amidotransferase inhibitor
Boy w/ self-mutilating behavior, low IQ, & gout
Lesch-Nyhan Syndrome (HGPRT def)
Orotic aciduria + hyperammonemia
Ornithine Transcarbamylase Deficiency
Orotic aciduria + normal serum ammonia
Orotic aciduria
Megaloblastic anemia that does not improve w/ folate or B12
Orotic aciduria
DNA Helicase
unwinds DNA during DNA replication
Topoisomerase
nicks DNA downstream to reduce the negative supercoils during DNA replication
Single Stranded Binding Proteins
Binds the the unwound DNA strands to stabilize the single strands
Which ABX class inhibits Topoisomerase?
Fluoroquinolones
Which chemotherapeutic agent inhibits Topoisomerase?
Etoposide
Etoposide is used to Tx?
solid tumors (Small cell lung carcinoma)
Auto-antibody that binds Topoisomerase?
Anti-Scl-70
Anti-Scl-70 is assoc w/
Diffuse Scleroderma
Primase
adds ribonucleotides to allow DNA pol III to bind
DNA polymerase III
binds double-stranded DNA and synthesizes in 5’->3’ direction (prokaryotes: both leading & lagging strand)
Primosome
DNA helicase + Primase complex
DNA polymerase I
removes ribonucleotides from RNA primer segment and replaces them w/ deoxyribonucleotides
DNA ligase
joints Okazaki fragments on lagging strand
Eukaryotic DNA pol alpha
synthesizes the lagging strand & synthesizes RNA primer
Eukaryotic DNA pol delta
synthesizes the leading strand
Eukaryotic DNA pol beta
DNA repair (Base-excision repair)
Eukaryotic DNA pol gamma
mitochondrial DNA replication
Silent mutation
single base mutation, often in the 3rd base –> same amino acid is coded
Missense mutation
single base mutation –> codes for a different amino acid
Nonsense mutation
single base mutation –> STOP codon
Frameshift mutation
addition/deletion mutation –> shifts reading frame
UV damage to DNA causes
pyrimidine dimer (thymidine cross-links on SAME DNA strand)
Mismatch repair
removes bases (including mismatched base) & replaces bases
Nucleotide excision repair
repair bulky DNA damage (UV damage)
Enzymes utilized in Nucleotide excision repair
endonuclease (removal/excision), DNA pol beta (insertion), DNA ligase (seals)
Base Excision Repair
removes just damaged base (small)
Enzymes utilized in Base excision repair
Glycosylase (removes damaged base)
Endonuclease (excises DNA backbone)
DNA pol beta & DNA ligase (insert/seal)
Non-Homologous End Joining
joins end of dsDNA break
Hereditary Nonpolyposis Colorectal Cancer - defective
mismatch repair
Xeroderma Pigmentosum - defective
nucleotide excision repair (UV light DNA damage)
Bloom Syndrome - mutation in
DNA helicase -> impaired DNA replication & repair
Ataxia Telangiectasia - defective
repair of dsDNA breaks (ionizing radiation DNA damage)
BRCA-1/-2 - defective
dsDNA break repair
Start codon
AUG -> Methionine
Stop codon
UGA, UAA, UAG
Which RNAs are synthesized in the nucleoplasm?
mRNA, tRNA
Which RNAs are synthesized in the nucleolus?
rRNA
Operon
transcribed gene + promoter + regulatory regions
Transcription factor
bind promoter regions (on/off)
What are the 3 main promoter regions?
-75 CCAAT box, -25 TATA box, -10 TATAAT box
Operator region
binds repressor or inducer, located b/w promoter and start site (on/off)
Response elements
enhancer or repressor region that increase or decrease the rate of transcription (rate control) may be located any distance from gene
Helix-loop-helix
allows protein to interact
Helix-turn-helix
allows protein to interact
Zinc finger
Zinc atom that incorporates into DNA
Leucine zipper protein
Many leucine residues, structural motif
What 2 conditions must be met for the lac operon to be turned on?
excess lactose + NO glucose
Lac operon activation causes transcription of
b-galactosidase
How does the absence of glucose contribute to turning on the lac operon?
when there is no glucose –> CAP (TF) binds the promoter region
How does excess lactose contribute to turning on the lac operon?
excess lactose –> lac repressor is released from the operator
Eukaryotic RNA pol 1
synthesizes rRNA
Eukaryotic RNA pol 2
synthesizes mRNA
Eukaryotic RNA pol 3
synthesizes tRNA
alpha-amanitin (mushroom toxin) inhibits
Eukaryotic RNA pol 2 leading to hepatotoxicity
Prokaryotic RNA pol
RNA pol 1 only
Which ABX inhibits RNA pol?
Rifampin
Hairpin Loop
termination of prokaryotic RNA transcription:
GC-rich regions of ssRNA binds forming a hairpin loop
Uracil rich region follows w/ weak bonds -> breaks off & RNA pol dissociates
Rho factor
RNA-dependent ATPase that knocks RNA pol off for termination of prokaryotic RNA transcription
S-adenosyl-methionine
attaches 7-methyl-guanosine cap to 5’ end of hnRNA
Poly-A-Polymerase
Adds adenines to 3’end of hnRNA
Spliceosome
splice out introns of hnRNA
mRNA processing requires
Addition of 5’ 7-methyl-guanosine cap
3’ Poly-adenosine tail
Splicing of introns
Aminoacyl tRNA synthase
matches amino acids to tRNA
Aminoacyl tRNA synthase always adds amino acids to
the 3’ end of the tRNA
Eukaryotic rRNA subunits
40S & 60S –> 80S
Prokaryotic rRNA subunits
30S & 50S –> 70S
50S subunit contains
23S ribosomal RNA
Initiation of translation
Initiation factor-2 (IF-1, IF-2, IF-3) binds 30S, then tRNA-Met, then binds 50S by hydrolyzing GTP
A site of the ribosome
binds all incoming aminoacyl tRNAs (except the 1st Met-tRNA)
P site of the ribosome
site of growing polypeptide chain (site where 1st Met-tRNA binds)
E site of the ribosome
exit site of free tRNA
Elongation factors
assist aminoacyl-tRNA binding to A site
Peptidyltransferase
w/in 23S rRNA
catalyzes the transfer of peptide chain from the P site to the a.a.-tRNA in the A site
Translocation
occurs during elongation, transfer tRNA form A to P site & slides the ribosome down to the next codon
Elongation factor-G
catalyzes translocation in prokaryotes
Elongation factor-2
catalyzes translocation in eukaryotes
What bacterial toxins inhibit EF-2?
Diptheria toxin & Exotoxin A
Termination
Release Factor causes dissociation of the polypeptide from the ribosome
Peptide modifications leading to functional protein
trimming, glycosylation, hydroxylation, phosphorylation
Which ABX binds the 30S subunit to prevent association w/ the 50S subunit?
Aminoglycosides
Which ABX bind 30S subunit to inhibit aminoacyl-tRNA from binding the A site?
Tetracyclines
Which ABX bind 50S subunit to inhibit peptidyltransferase?
Chloramphenicol
Which ABX bind 50S subunit to inhibit association w/ 30S?
Linezolid
Which ABX bind 50S subunit to inhibit translocation?
Macrolides, Clindamycin, Lindomycin, Streptogramin
AD pedigrees
M & F are affected, 50% of offspring, every generation
AR pedigrees
Non-successive generations, 25% of offspring
X-linked Recessive pedigrees
Typically only Males affected; females 50% of carrier, males of offspring 50% affected
X-linked Dominant pedigrees
all daughters of affected males will be affected
Mitochondrial Inheritance pedigrees
all offspring of affected mom will be affected
Anticipation
age of onset is earlier or more severe w/ successive generations
What disease is an example of anticipation?
Huntington Disease
Incomplete Penetrance
how often a mutant genotype causes a mutant phenotype
Pleiotrophy
1 gene causes many different effects (PKU)
Locus Heterogeneity
multiple mutations could cause the same phenotype (Marfans)
Codominance
both alleles are equally expressed (ABO type)
Variable expression
severity of phenotype varies in individuals (tuberous sclerosis)
Imprinting
phenotype differences depend on whether mutation came from mom or dad (angel man & prader-willi)
Prader-Willi Syndrome
maternal imprinting + paternal deletion on chromosome 15
Angelman Syndrome
paternal imprinting + maternal deletion on chromosome 15
Hardy-Weinberg Eq
p+q = 1
p^2 + 2pq + q^2 = 1
Northern blot
gel electrophoresis RNA samples + DNA probe
Southern blot
gel electrophoresis DNA samples + DNA probe
Western blot
gel electrophoresis protein samples + Antibody probe
Southwestern blot
DNA binding proteins
Direct ELISA
antibody in well + sample (Ag)
Does pt have X antigen?
Indirect ELISA
antigen in well + sample (Ab)
Does pt have X antibody?
Screening test for HIV?
Indirect ELISA
Confirmatory test for HIV?
Western blot
Kayotyping
Dx chromosomal imbalance
GLUT-1
found on RBCs & BBB
mediates basal glucose uptake