usmle: biochem I
Terms
undefined, object
copy deck
- what are the three posttranscriptional modifications
-
1. 7-methyl guanine cap on 5' end
2. addition of the 3' poly-A tail
3. removal of introns - what aa is the major carrier of N byproducts from most tissues in the body
- glutamine
- what two aa have a pKa of 4
- aspartic acid and glutamic acid
- how many acetyl CoAs per glucose enter into the TCA cycle
-
2 acetyl CoA per glucose
12 ATPs per acetyl Coa - what topoisomerase makes ssDNA cuts, requires no ATP, relazes supercoils, and acts as the swivel in front of the replication fork
- topoisomerase I (relaxase)
- in prokaryotes , what is the name of the RNA sequence that ribosomes bind to so translation can occur
- shine-Delgarno
- name the pattern of genetic transmission; both M and F are affected; M-to-M transmission may be present; both parents must be carriers; the trait skips generations; two mutant alleles are needed for disease; and affected children may be born of unaffecte
- autosomal recessive
- what factors are needed for translation of prokaryotes
- elongation factor G and GTP
- what three aa must patients w/ maple syrup urine disease not eat
-
isoleucine
leucine
valine
(I Love Vermont maple syrup)
dec alpha-ketoacid dehydrogenase - how many high energy bonds are used to activate an aa
- 2 ATPs via the amino-acyl tRNA synthase enzyme
- what water-soluble vitamin deficiency results in pellagra
- niacin (B3)
- what glycolytic enzyme has a high Vmax, high Km, and low affinity for glucose
- glucokinase
- how many ATPs are generated per acetylCoA
- 12
- what cytoplasmic pathway produces NADPH and is a source of ribose-5-phosphate
- HMP shunt
- what is the main inhibitor of pyruvate dehydrogenase
- AcCoA (pyruvate to AcCoA)
- where on the codon and anticodon does the wobble hypothesis take place
- 3' end of the codon (3rd position) on mRNA and 5' end on anticodon (first position) on tRNA
- what DNA excision and repair enzyme is deficient in patients with xeroderma pigmentosum
- excision endonuclease- removes thiamine dimers
- what form of bilirubin is carried on albumin
- unconjugated (indirect)
-
what are the
two ketogenic AAs - leucine and lycine
- which organisms have polycistronic mRNA
- prokaryotes
- as what compound do the carbons for fatty acid synthesis leave the mito
- citrate via the citrate shuttle
- what four substances inc the rate of gluconeogenesis
-
1. glucagon
2. NADH
3. AcCoA
4. ATP - with what three enzymes is TPP assoc
-
1. alpha-ketoglutarate dehydrogenase
2. pyruvate dehydrogenase
3. transketolase - what test uses very small amounts of DNA that can be amplified and analyzed without the use of southern blottin gor cloning
- PCR
- what apoprotein is required for the release of chylomicrons from the epithelial cells into the lymphatics
- apo-B-48
- what enzyme catalyzes the covalent bonding of the aa's carboxyl grouop to the 3' end of tRNA
- aminoacyle-tRNA synthetase uses 2 ATPs
- what must be supplemented in patients with medium-chain acyl CoA dehydrogenase (MCAD) deficiency
- short chain fatty acids
- what form of aa is found only in collagen
- hydroxyproline
- in a diabetic patient, to what does aldose reductase convert glucose
- sorbitol (-> cataracts)
- what enzyme catalyzes the rate-limiting step in cholesterol metabolism
- HMG-CoA-reductase
- what is the term for the pH at which the structure carries no charge
- pI
- what enzyme catalyzes the rate-limiting step in gluconeogenesis
- fructose-1,6-bisphosphatase
- what is the dug of choice in treating a patient with hyperuricemia due to underexcretion of uric acid
- probenecid, a uricosuric agent
- what enzyme deficiency results in darkening of the urine when exposed to air
- homogentisate oxidase deficiency is seen in patients w/ alcaptonuria
- in eukaryotes, what transcription factor binds to the tATA box before RNA pol II can bind
- transcription factor IID
- what enzyme produces an RNA primer inthe 5'-3' direction and is essential to DNA replication because DNA polymerase are unable to synthesize DNA without an RNA primer
- primase
- what enzyme catalyzes the rate-limiting step in fatty acid synthesis
- AcCoA carboxylase
-
name the eukaryotic DNA polymerase based on the following info
1. replicates mito DNA
2. synthesizes lagging strand
3. synthesizes leading strand -
1. dna pol-gamma
2. dna pol-alpha
2. dna pol-delta - what is the order of fuel use in a prolonged fast
-
glucose from liver glycogen
glucose from gluconeogenesis
body protein
body fat - which way will the O2 dissociation curve shift with the addtion of 2.3BPG to adult Hb
- right
-
what enzyme of pyrimidine synthesis is inhibited by the following
1. 5-FU
2. methotrexate
3. hydroxyurea -
1. thymidylate synthase
2. dihydrofolate reductase
3. ribonucleotide reductase -
what is found in the R group if the aa is acidic?
basic? -
if a carboxyl group is the R group- acidic
if an amino group is the R group- basic - what gluconeogenic mitochondrial enzyme rquires biotin
- pyruvate carboxylase
- what factors are needed fro translocation in eukaryotes
- ef-2 and GTP
- DNA replication occurs during what phase of the cell cycle
- S phase
- what is the end product of purine catabolism
- uric acid
- what causes transcription to stop in eukaryotes
-
the termination sequence on the DNA
stop codons stop translation -
what enzyme of the TCA cycle catalyzes ...
1. FADH2
2. GTP
3. NADH -
1. succinate dehydrogenase
2. succinyl CoA synthetase
3. isocitrate dehydrogenase
alpha-ketoglutarate dehydrogenase
malate dehydrogenase - what form of alcohol causes blindness
- methanol (wood alcohol)
- how many base pairs upstream is the TATA box promoter
-
-10
there is another promoter -35 - what are the two essential fatty acids
- linoleic and linolenic acid
- during a prolonged fast, why is the brain unable to use FAs
- FAs can't cross the bbb, therefore they can't be used as an energy source
- what type of jaundice is seen in Rotor's syndrome
- conjugated (direct)
- if a sample of DNA has 30% T, what is the percent of C
-
20%
(chargaff's rule) - from where is the energy for gluconeogenesis derived
- beta-oxidation of FAs
-
name the type of mutation
1. deletion or addition of a base
2. new codon specifies a different aa
3. unequal crossover in meiosis w/ loss of protein function
4. new codon specifies for the same aa
5. new codon specifies for a sto -
1. frameshift
2. missense
3. large segment deletion
4. silent
5. nonsense - what form of bilirubin can cross the bbb
- unconjugated free bili
- what aa is brokin down into N2O causing an inc in cGMP of sm mm, hence vasodilation
- arginine
- what is needed to produce a double bond in a fatty acid chain in the ER
- NADPH, O2, cythochrome b5
- what are the vitamin K dependent coagulation factors
-
II
VII
IX
X
protein C and S - is the hydroxyl (-OH) end of DNA and RNA at the 3' or 5' end
- 3'
-
how many codons code for aa?
how many for termination of translation? -
61
3 (UGA, UAA, UAG)
(you go away, you are away, you are gone) - what is the enzyme for the oxidative reaction in glycolysis
- glyceraldehyde dehydrogenase
- what substrate builds upin Tay-Sachs disease
- Gm2 ganglioside
- what pattern of genetic transmission is characterized by no transmission from M, maternal inheritance, and the potential for the disease to affect both sons and daughters of affected F
- mito
- what is the rate limiting step of glycogen synthesis
- glycogen synthase
- what sphingolipid is formed by the union of serine and palmitoyl CoA
- sphingosine
- what causes an inc in bone mineralization and Ca along with PO4 absorption from the GI tract andkidney tubules
- vitamin D
- what two sugars can be used to produce cerebrosides
- glucose and galactose
- what group of eukaryotic regulatory proteins has a major factor in controlling the gene expression embryonically
- homeodomain proteins
- what causes the lysis of RBCs by oxidizing agents in G-6-PD deficiency
- lack of glutathione peroxidase activity -> dec in NADPH -> leaves glutathione reduced
- all aa's have titration plateaus at what pH values
- 2 and 9
- what cytoplasmic organelle carries the enzymes for elongation and desaturation of fatty acyl CoA
- SER
- what is the binding site for RNA pol
- the promoter indicates where transcription will begin
- what vitamin is necessary for epithelial health
- A
- what lipoprotein is formed if an IDL particle acquires cholesterol from a HDL particle
- LDL
- what structure or a protein describes the interaction among subunits
- quaternary
- what is the only factor of enzyme kinetics that the enzyme affects
- Ea (activation energy)
- is the lac operon activated or inactivated in the presence of both glucose and lactose
-
inactivated
glucose results in dec cAMP and therefore blocks protein binding between cAMP and CAP - at the end of each round of beta-oxidation, what is released
-
AcCoA
FADH
NADH - what is the rate limiting step of glycolysis
- PFK1 and costs 1 ATP
- what enzyme of heme synthesis is deficient in autosomal dominant disorder acute intermittent porphyria
- uroporphyrinogen-I synthase
- what enzyme is blocked by disulfiram
- aldehyde dehydrogenase
- deficiencies in what enzyme result in insoluble glycogen synthesis formation
- alpha-1,6-transferase
-
what eukaryotic translation enzyme is associated w/...
1. initiation
2. elongation
3. termination -
1. eIF-2 in the P-site
2. eEF-1
3. no enzymes are needed - what aa undergoes N-glycosylation
- asparagine
- what enzyme, induced by insulin and activated by apo C-II, is req for chylomicron and VLDL metabolism
- Lipoprotein lipase
- what is the most common genetic deficiency resulting in hemolytic anemia
-
G-6-PD deficiency,
2nd is pyruvate kinase def -
are the following condtions assoc w/ neg or pos N balance
1. aa def
2. growth
3. preg
4. uncontrolled DM
5. starvation
6. infection
7. recovery from injury
8. kwashiorkor -
1. neg
2. pos
3. pos
4. neg
5. neg
6. neg
7. pos
8. neg - why is the liver unable to metabolize ketone bodies
- hepatocytes lack the succinyl CoA acetoacetyl CoA transferase (thiophorase)
- what enzyme, induced by insulin and activated by apo C-II is required for chylomicron an dVLDL metabolism
- lipoprotein lipase
- what is the MC genetic deficiency resulting in hemolytic anemia
-
G-6-PD def
pyruvate kinase is 2nd -
are the following conditions associated with a negative or pos N balance
1. aa def
2. growth
3. preg
4. uncontrolled DM
5. starv
6. infec
7. recovery from injury
8. kwashiorkor -
1. neg
2. pos
3. pos
4. neg
5. neg
6. neg
7. pos
8. neg - what toxin ADP-ribosylates via Gs protein to inc cAMP
- cholera toxin
- what two viatmins are inactivated when they come in contact with acetaldehyde
- thiamine and folate
-
name the end product of FA synthesis?
FA oxidation -
palmitate
AcCoA and propionyl Coa (odd chain FAs) - what is the term for production of a DNA copy from an RNA molecule
- reverse transcription
- what mineral is req for cross-lining of collagen molecules into fibrils
- lysyl oxidase requires Cu and O2
- how many high energy bonds does the cycle of elongation cost
-
4
2 from ATP in aa activation
2 from GTP - what enzyme of purine synthesis is inhibited by allopurinol and 6-mercaptopurine
- PRPP aminotransferase
-
t or f
the urea cycle takes place in both the cytoplasm and the mito -
t
carbamoyl phosphate synthtesase and ornithine transcarbamoylase are mito enzymes - what is the only FA that is gluconeogenic
- propionic acid
-
what enzyme has 5' to 3' synth of okazaki fragments
3' exonuclease activity
5' exonuclease activity - dna pol I
- in what organelle does the TCA cycle occur
- mito
- what enzyme is deficient in selective T cell immunodeficiency
- purine nucleoside phosphorylase
-
t or f
adipose tissue lacks glycerol kinase -
t
adipose depends on glucose uptake for dihydroxyacetone phophate (DHAP) production for TG synthesis - in what form is excess folate stored in the body
- N-5-methyl THF
- what is the term for taking an mRNA molecule and arranging the aa sequence forming a protein
- translation
- what enzyme is blocked by hydroxyurea
- ribonucleotide reductase
- what protein carries free fatty acids to the liver
- albumin
- what substrate is built up in Neimann-Pick
- sphingomyelin
-
t or f
methylation of bacterial DNA prevents restriction endonuclease from cutting its own chromsomes - true
- what two aa's have a pka of 10
- lysine and tyrosine
- what is the only enzyme in the body that uses N-5-methyl folate
- homocysteine methyl transferase
- how can you differentiate vitamin K from vitamin C deficiency
-
K- nl bleeding time, inc PT
C- inc bleeding time, nl PT - what is the term for a unit of DNA that encodes a particular protein or RNA molecule
- a gene
- is the coding or the template strand of DNA identical to mRNA (excluding the T/U diff)
-
coding strand
the template strand is complementary and antiparallel) - what enzyme is deficient in acute intermittent porphyria
- uroporphyringoen I synthetase
- what five cofactors and coenzymes are required by pyruvate dehydrogenase
-
1. B1: thyamine -> TTP
2. B2: riboflavin -> FADH2
3. B3: niacin -> NAD(H)
4. B5: pantothenate -> CoA
5. lipoic acid