USMLE biochemistry Flashcards

Terms Definitions
Inactivates cAMP
What is this structure?
What water-soluble-vitamin deficiency is associated with poor wound healing, easy bruising, bleeding gums, anemia, and painful glossitis?
Vitamin C
Are the following conditions associated with a negative or positive nitrogen balance?• Recovery from injury
Ribonucleotide reductase
Makes deoxyribonucletides from ribonucleotides. Inhibited by hydroxyurea
Ketogenic enzymes
AcetoacetylCoA synthase, HMG-CoA synthase, HMG-CoA lyase
Gluthathione reductase
Reduces gluthathione using NADPH
What AA is a phenol?
What gluconeogenic mitochondrial enzyme requires biotin?
Pyruvate carboxylase
What enzyme catalyzes the rate-limiting step in cholesterol metabolism?
HMG-CoA reductase
Pyruvate kinase
Substrate-level phosphorylation of ADP using energy from PEP. Produces pyruvate and ATP. Activated by fructose-1,6BP.
ATPase that links peripheral 9 doublets to bend and slide cilium. Responsible for retrograde transport. Defective in Kartagener
Secreted by epithelial cells of intestine along with chylomicrons to allow their exit to lymph and tissues
postranslational modifications
N-linked and O-linked glycosylation, phosphorylation of tyrosine, serine, threonine residues, sulfation, methylation and acetylation of lysine residues, gamma-carboxylation of glutamate, myristoylation of glycine, palmitoylation and fernasylation of cysteine; all happen in the Golgi complex
Hormone-sensitive lipase
Hydrolizes triglycerides to glycerol and fatty acids in adipose tissue. Activated by decreased insulin, increased epinephrine and cortisol. Inhibited by niacin.
What cytoplasmic pathway produces NADPH and is a source of ribose 5-phosphate?
HMP shunt
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 blotting technique uses the following for analysis?• Protein
Western blot
What enzyme is blocked by hydroxyurea?
Ribonucleotide reductase
What group of eukaryotic regulatory proteins has a major factor in controlling the gene expression embryonically?
Homeodomain proteins
Vitamin A toxicity
Alopecia, dry skin, hepatomegaly, hyperlipidemia
cis regulators
core promoter sequence (TATA, BRE, DPE), proximal promoter region (GC box, CCAAT box), enhancers, silencers, insulators, response elements (CRE, SRE, IRE, GRE, PRE, HSRE, HMRE)
Vitamin B6 deficiency
Induced by isoniazid and contraceptives - peripheral neuropathy, seizures
Activated by ApoA-1from HDL. Binds a fatty acid to cholesterol to produce an ester that dissolves into the HDL for reverse transport to liver
Important fatty acids
Linoleic acid: C18:2(9,12); Linolenic acid: C18:3(9,12,15); Arachidonic acid C20:4(5,8,11,14); Palmitic acid: C16:0
What protein carries free fatty acids to the liver?
What protein is required by prokaryotic RNA polymerases to initiate transcription at the promoter region of DNA?
Sigma factor
What enzyme is blocked by hydroxyurea?
Ribonucleotide reductase
What fat-soluble vitamin is connected to selenium metabolism?
Vitamin E
What blotting technique uses the following for analysis?
Southern blot
What enzyme is deficient in the following glycogen storage disease?
• von Gierke's disease
What is the most abundant amino acid in collagen?
What enzyme is deficient in acute intermittent porphyria?
porphobilinogen deaminase
Name the RNA subtype based on the following:• Found only in the nucleus of eukaryotes and functions to remove introns from mRNA
What enzyme produces an RNA primer in the 5'-3' direction and is essential to DNA replication because DNA polymerases are unable to synthesize DNA without an RNA primer?
What form of alcohol causes blindness?
Methanol (wood alcohol)
Heinz bodies formation
H2O2 acumulates and denatures Hb because of lack of G6PDH and reduced gluthathione
Hypoglycemia induced by alcoholism
Alcohol metabolism produces excess NADH which interferes with gluconeogenesis by 1. favoring lactate formation from pyruvate; 2. Shifting the malate shuttle into the mitochondria; 3. Forming glycerol 3P from DHAP
Ketogenic and glucogenic AA
Phe, Tyr, Try, Ile, Thr
Pathophsysiology of atherosclerosis
1. Endothelial lesion produced by blood turbulence, elevated LDL, free radicals from cigarette smoke, homocystenemia, diabetes (glycosylation of LDL) and hypertension.; 2. Inflamed endothelium recruits monocytes and macrophages and platelet adhesion; 3. Production of ROS by macropahges oxidizes LDL; 4. Macrophages become cholesterol-laden (foam cells) after phagocytosis of LDL, producing fatty streaks; 5. Fatty streak enlarges with necrotic debris, lipids, epitheloid and smooth muscle cells producing an advanced plaque and ocluding blood vessel with subsequent ischemia; 6 The plaque can rupture with subsequent thrombosis
Thymidilate synthetase
Makes dTMP which is the deNovo precursor of DNA nucleotides. Requires methylTHF
Vitamin D excess
Results in hypercalcemia, stupor; Seen in sarcoidosis due to macrophage conversion of vit D into active form
Glucose 6 phosphatase
Converts glucose 1-P to glucose 6-P
Fructose metabolism
Bypases PFK-1 and therefore has the highest metabolic rate
What enzyme requires molybdenum as a cofactor?
Xanthine oxidase
What AA is broken down into N2O, causing an increase in cyclic guanosine monophosphate (cGMP) of smooth muscle, hence vasodilation?
Name the RNA subtype based on the following:
• Carries AA to the ribosome for protein synthesis
What is the drug of choice for treating a patient with hyperuricemia due to overproduction of uric acid?
What AA is a precursor of the following substances?
What form of bilirubin is carried on albumin?
Unconjugated (indirect)
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?
Thymidylate synthase
makes dTMP out of dUMP in pyrimidine synthesis; inhibited by 5-fluoracil
AMPA receptor
binds glutamate and allows Ca and Na influx and K efflux; responsible for excitotoxicity
HbC versus HbS
HbS is formed by replacement of glutamic acid by valine (neutral); HbC is formed by replacement of glutamic acid by lysine (positively charged). Therfore HbC moves less than HbS in electrophoresis.
What are the positively charged basic AA
Lysine, arginine, histidine
Signal sequence required by proteins destined to be secreted, placed on cell membrane or directed to lysosome
N-terminal hydrophobic signal sequence
Define: promoter region
The binding site for RNA polymerase. AT-rich sequence with TATA and CAAT boxes
Inhibitors of ethanol metabolism
Fomepizole (inhibits alcohol DH) and disulfram (inhibits acetaldehyde DH)
What enzyme is used to remove the hairpin loop during production of cDNA from mRNA?
S1 nuclease
What component of the ETC is inhibited by the following?
• Oligomycin
Fo/F1 complex
What is the term for taking an mRNA molecule and arranging the AA sequence forming a protein?
What type of jaundice is seen in Rotor's syndrome?
Conjugated (direct) hyperbilirubinemia
Is linolenic acid an omega-3 or omega-6 fatty acid?
Omega-3; linoleic is omega-6
Mechanism of action: Gq receptor
1. Activates phospholipase C; 2. Releases IP3 and DAG from membrane; 3. IP3 releases intracellular Ca+; DAG activates protein kinase C
DNA repair: Thymine dimers
1. UV light creates thymine dimers during G1; 2. Removed by excision endonuclease which is deficient in XP; 3. Patched by DNA polymerase and ligase.
Cherry-red spots in macula, blindness, psychomotor retardation, death before 2 years
Tay SaXhH. Deficiency of Hexosaminidase A. Ganglioside acumulates
Under which influence do phosphofructokinase inhibit the rate of glycolysis
Under the influence of glucagon (PFK-2) (increase cAMP/protein kinase A/phosphorylation) and ATP/citrate (PFK-1). Phosphorylated states noncompetitively inhibit PFK, lowering Vmax, lowering rate of glycolysis
What is a silent mutation?
New codon codes same amino acid
Substrate-level phosphorylation reaction of oxidative phosphorylation
Succinyl CoA + GDP + succinyl CoA synthetase --> succinate + GTP
What enzyme of the TCA cycle catalyzes the substrate level phosphorylation?
Succinyl CoA synthetase
What eukaryotic translation enzyme is associated with the following:
• Initiation
eIF-2 in the P site
Name three purine bases that are not found in nucleic acids.
Xanthine, hypoxanthine, theophylline, theobromine, caffeine, and uric acid are all purines.
All AAs have titration plateaus at what pH values?
pH of 2 and 9
What mineral is required for cross-linking of collagen molecules into fibrils?
The enzyme lysyl oxidase requires Cu2+and O2 to function properly.
Important reactions in oxidative stress
O2 + NADPH oxidase --> superoxide radical
superoxide radical + superoxide dismutase --> H2O2
H2O2 + catalse --> H2O + O2
H2O2 + Cl- + myeloperoxidase --> hypochlorite
What is the function of ubiquitin?
Covalently binds to misfolded proteins to signal their destruction by proteasome
Milestones in brain energy metabolism
12 hours: glucose from glycogen; 1 week: glucose from gluconeogenesis; beyond 1 week: ketone bodies
T-type Ca channel
located in the SA and AV nodes (phase 4) and in the thalamus (ethosuximide)
What enzyme has a 5' to 3' synthesis of the Okazaki fragments, 3' exonuclease activity, and 5' exonuclease activity?
DNA polymerase I
What two enzymes of heme synthesis are inhibited by lead?
ALA dehydrogenase and ferrochelatase
How many ATPs are produced from cytoplasmic NADH oxidation using the malate shuttle?
3 ATPs by oxidative phosphorylation
What is the binding site for RNA polymerase?
The promoter indicates where transcription will begin.
What two AAs have a pKa of 4?
Aspartic acid and glutamic acid
What three bases are pyrimidines?
1. Cytosine 2. Uracil (only in RNA) 3. Thymidine
What is a peptide bond?
Bond between carboxyl group of one AA to amino group of another AA
Reactions in the malate shuttle
OAA + NADH (cytoplasm) --> malate + NAD; malate enters mitochondria
What are the 6 types of RNA
1. rRNA: structural component of ribosome (most common); 2. tRNA: carries amino acids to ribosome; 3. mRNA: contain info for AA sequence; 4. hnRNA precursor of mRNA; 5. snRNA: splices mRNA; 6. Ribozymes: RNA molecules w/enzymatic activity
What purine base is contained in inosine monophosphate?
Hypoxanthine (remember, IMP is a precursor for AMP and GMP)
Which shuttle is used to bring fatty acyl CoA from the cytoplasm for ketogenesis?
Carnitine acyl CoA transferase II
What is the drug of choice in treating a patient with hyperuricemia due to underexcretion of uric acid?
Probenecid, a uricosuric agent
What is the only organ in the body that can produce ketone bodies?
The liver (in the mitochondria)
Protein synthesis: describe elongation process
1. Charged tRNA binds A site and mRNA codon; 2. Peptide bond by peptydyl transferase (uses 2 high energy bonds from aminoacyl-tRNAs); 3. tRNA is removed from P site/growing peptide; 4. ribosome moves 5'-3' exactly one codon. Translocation requires EF-2 (inactivated through ADP-rybosylation by Pseudomona and diptheria toxins)
During a prolonged fast, why is the brain unable to use fatty acids?
Fatty acids cannot cross the blood-brain barrier; therefore, they cannot be used as an energy source.
Where on the codon and anticodon does the wobble hypothesis take place?
3'end of the codon (third position) on mRNA and 5' end of the anticodon (first position) on tRNA.
Donators of NH2 and C to urea molecule
aspartate --> NH2; NH4+ --> NH2; CO2 --> C
What form of continuous DNA, used in cloning, has no introns or regulatory elements?
cDNA, when it is made from mRNA
True or false? There is no hormonal control to the TCA cycle.
True. The energy status of the cell dictates if the cycle is running or relaxing.
What two AAs do not have more than one codon?
Methionine (start) and tryptophan are the only two AAs with only one codon.
What is the order of fuel use in a prolonged fast?
1. Glucose from liver glycogen 2. Glucose from gluconeogenesis 3. Body protein 4. Body fat
What is the order of fuel use in a prolonged fast?
1. Glucose from liver glycogen
2. Glucose from gluconeogenesis
3. Body protein
4. Body fat
If a sample of DNA has 30% T, what is the percent of C?
Solved as 30% T + 30% A = 60%; therefore, C + G = 40%; then C = 20% and G = 20% (example of Chargaff's rule)
Sulfur-containing AA
Cysteine, methionine
Nissl bodies
RER of neurons
intermediate filament of epithelial cells
B12 deficiency
Megaloblastic anemia, neuropathy, homocystinemia, methylmalonic aciduria. Needed by methylTHF-homocysteine methyl transferase and malonyl CoA mutase. Pernicious anemia, D. latum, ileum resection, Crohn's
Complex II of ETC
Succinate dehydrogenase
Aromatic AAs
Tyr, phe (essential), trp
Consequence of hyperammonemia
ornithinetranscarbamoyl synthase deficiency or liver disease --> hyperammonemia --> depletion of alpha-ketoglutarate --> inhibition of TCA cycle
Are the following conditions associated with a negative or positive nitrogen balance?
• AA deficiency
Gluthathione peroxidase
Oxidizes H2O2 using reduced gluthathione
Pompe disease
Lysosomal alpha 1,4 glucosidase deficiency. Cardiomegaly, glycogen inclusion bodies.
What enzyme catalyzes the rate-limiting step in gluconeogenesis?
Fructose-1, 6-bisphosphatase
What lysosomal enzyme is deficient in
• Gaucher's disease?
What pyrimidine base is produced by deaminating cytosine?
Name the lipoprotein based on the following characteristics.• apo E, apo B-100, apo C-II
Name the type of mutation:• New codon specifies for the same AA
What enzyme of pyrimidine synthesis is inhibited by the following?• Hydroxyurea
Ribonucleotide reductase
Name the eukaryotic DNA polymerase based on the following information:• Synthesizes the lagging strand during replication
DNA polymerase-α
What pyrimidine base is found• Only in DNA?
PRPP synthase
Makes PRPP from ribose-5-phosphate in purine synthesis.
Hepatosplenomegaly, bone erosion, fractures, pancytopenia
Gaucher. Glucocerebroside deficiency. Glucocerebroside acumulates.
alternative RNA splicing
spliceosome combines exons in different ways producinf different isoforms of the protein
Neonatal ketoacidosis
Propionyl coa Carboxylase or methyl malonyl CoA mutase deficiency. Cant metabolize val, met, ile, thr through propyonyl acid cycle
Receptors/second messengers used by atrial natriuretic peptide
Guanylate cyclase pathway
What are the acidic, negatively charrged AA
Aspartate, glutamate
Carried by HDL, activates LCAT and PCAT (blood enzymes) to hydrolize fatty streak cholesterol by attaching a fatty acid to it (esterification) so that it dissolves into HDL for reverse transport from tissues to hepatocyte
What organ functions to keep blood glucose levels normal through both well-fed and fasting states and produces ketones in response to increased fatty acid oxidation?
Cri-du-chat syndrome results in a terminal deletion of the short arm of what chromosome?
Chromosome 5
What pyrimidine base is produced by deaminating cytosine?
1-α-Hydroxylase activity is increased in response to what two physiologic states? (hint: think of vitamin D activity)
Hypocalcemia and hypophosphatemia
Name the pattern of genetic transmission characterized thus: both M and F affected; no M-to-M transmission; affected M passes trait to all daughters, every generation; affected F passes trait to both sons and daughters; a single mutant allele can produce
X-linked dominant
What hormone is activated in adipose tissue when blood glucose levels decrease?
Hormone-sensitive lipase
What is O-linked glycosylation?
Proteins acquire oligosacchride side chains attached to serine or threonine residues
Permanent cells
Remain in G0, regenerate from stem cells; neurons, skeletal and cardiac muscle, RBCs
Sodium benzoate, phenylpyruvate
Treatment of urea cycle enzyme deficiencies. Provides alternative route for capturing and excreting excess nitrogen
Digestion of lipids
1. Bile emulsifies lipids; 2. pancreatic lipase, colipase and cholesterol esterase degrade lipids to 2-monoglyceride, fatty acids and cholesterol; 3. Absorbed and re-esterified to TG and cholesterol esters; 4. Packaged with Apo-B48 into chylomicrons
NMDA receptor
require glutamate and glycine to allow Na and Ca influx and K efflux; irreversible antagonists: amantadine and memantine; reversible antagonists: ketamine and PCP
Von Gierke disease
Deficiency of glucose 6 phosphatase. Severe hypoglycemia, lactic acidosis, hepatomegaly, hyperuricemia
What is the pyrimidine intermediate that joins PRPP (5-Phosphoribosyl-1-Pyrophosphate)?
Orotic acid
(purine metabolism)
What vitamin is an important component of rhodopsin?
Vitamin A
What enzyme of purine synthesis is inhibited by allopurinol and 6-mercaptopurine?
PRPP aminotransferase
What structure of a protein describes the interaction among subunits?
Quaternary structure
What enzyme of the purine salvage pathway is deficient in the following?• Selective T-cell immunodeficiency
Purine nucleoside phosphorylase
Name the type of mutation:• Unequal crossover in meiosis with loss of protein function
Large segment deletions
What enzyme is deficient in selective T cell immunodeficiency?
Purine nucleoside phosphorylase
DeNovo cholesterol synthesis
2 Aacetyl CoA provided by citrate shuttle + NADPH --> acetoacetyl CoA + HMG-CoA synthase --> HMG-CoA + HGM-CoA reductase --> mevalonate -->--> farnesyl ppi -->--> cholesterol.
Carbamoyl phosphate synthase 2
Located in the cytoplasm. Makes carbamoyl phosphate from CO2 + glutamine in pyrimidine synthesis.
Metabolism of homocysteine
Can be converted to cysthathione by cysthathione synthetase and then cysteine (requires B6). Or it can be converted into methionine (requires B12 and 5-methylTHF)
Labile cells
Never go to G0; bone marrow, gut epithelium, skin, hair follicles
Outcome of ETC inhibition
1. Decreased oxygen consumption; 2. Increased intracellular NADH and FADH2; 3. Decreased ATP
What determines the rate of reaction?
The energy of activation
Via what cell surface receptor does HDL cholesterol from the periphery enter hepatoceles?
Scavenger receptor (SR-B1)
What enzyme catalyzes the covalent bonding of the AA's carboxyl group to the 3' end of tRNA?
Aminoacyl-tRNA synthetase, which uses 2 ATPs for this reaction.
In what cycle does glucose go to the muscle, where it is converted to pyruvate and then into alanine before being taken back to the liver?
Alanine cycle
Mechanism of action: Daunorubicin, doxorubicin
Intercalate between bases of DNA interfering with activity of topoisomerase II (DNA gyrase), preventing replication
What does phosphorylation of manose residues do? I-cell disease?
Manose residues on oligosacchride chain are phosphorylated in golgi aparatus to direct the enzyme to lysosome. In I-cell disease, lysosomal enzymes are secreted into extracellular space due to inappropriate phosphorylation of manose residues
Mechanism of action: Gs receptor
1. Activates adenyl cyclase; 2. Increased cAMP; 3. Phosphorylation of protein kinase A and CREB
Biochemistry of vision
1. When rhodopsin Gt receptor is not stimulated by light, there are high levels of GMP in the rod cell. GMP activates Na-gated channels which partially depolarize the rod, releasing inhibitor glutamate on bipolar cells of optic nerve. 2. Upon light stimulation, rhodopsin Gt receptor decreases GMP, hyperpolarizes the cell and stops glutamate inhibition of bipolar cells
Direction of replication and transcription
5'-3'. The incoming nucleotide bears the triphosphate in 5' that attaches to the 3' hydroxyl of nascent peptide
Mention the vitamin K-dependant factors
Factors II (prothrombin), VII, IX, X
Which of the following—DNA methylating enzymes, scaffolding proteins, histone acetylases, or deacetylases—is a regulator of eukaryotic gene expression?
Histone acetylases is a regulator favoring gene expression. All of the others favor inactivation.
What part of the 30S ribosome binds to the Shine-Dalgarno sequence?
16S subunit
What type of bilirubin is found in neonatal jaundice?
Indirect or unconjugated
In what cycle does glucose go to the muscle, where it is converted to pyruvate and then into alanine before being taken back to the liver?
Alanine cycle
What is the rate-limiting step of the following?
• Fatty acid synthesis
Acetyl CoA carboxylase
What is the most common genetic deficiency resulting in hemolytic anemia?
G-6-PD deficiency; pyruvate kinase deficiency is second.
What is the drug of choice in treating a patient with hyperuricemia due to underexcretion of uric acid?
Probenecid, a uricosuric agent
How many ATPs are produced from cytoplasmic NADH oxidation using the glycerol phosphate shuttle?
2 ATPs by oxidative phosphorylation
How does cyanide poisoning inhibit glycolysis?
Complex IV is inhibited, NADH acumulates and inhibits isocitrate DH, citrate acumulates and inhibits PFK-1
What are the ketone bodies and what tissues metabolize them?
Acetoacetate and B-hydroxybutirate metabolized by muscle, cardiac muscle and renal cortex. Brain metabolizes them after 1 week of fasting
What is the direction of transcription?
reads template strand 3'-5'. makes mRNA 5'-3'
With what three enzymes is thiamin pyrophosphate (TPP) associated?
1. α-Ketoglutarate dehydrogenase
2. Pyruvate dehydrogenase
3. Transketolase

Thiamine pyrophosphate (TPP) functions as a coenzyme vital to tissue respiration. It is required for the oxidative decarboxylation of pyruvate to form acetyl-coenzyme A, providing entry of oxidizable substrate into the Krebs cycle for the generation of energy
Where in the body is heme converted to bilirubin?
RES(Reticular endothelial system)
What DNA replication enzyme breaks the hydrogen bond of base pairing, forming two replication forks?
Helicase (requires ATP for energy)
What three vitamin deficiencies are associated with homocystinemia?
Folate, vitamin B12, and vitamin B6
What is needed to initiate translation?
IF and GTP (eIF for eukaryotes)
What substrate builds up in Tay-Sachs disease?
GM2 gangliosideCaused by a deficiency of β-hexosaminidase A
What is a large segment deletion? Mention two examples
Unequeal crossover in meiosis. Ex. Alpha thalasemia: deletion of alpha globin gene from chromosome 16; Cri-du-chat: 5q deletion
Vitamin K dependant factors
II, VII, IX, X and proteins C and S
True or false? Adipose tissue lacks glycerol kinase.
True. Adipose depends on glucose uptake for dihydroxyacetone phosphate (DHAP) production for triglyceride synthesis.
Why are eukaryotes unable to perform transcription and translation at the same time like prokaryotes?
In eukaryotes transcription occurs in the nucleus and translation in the cytoplasm.
What elongation factor is inactivated by ADP ribosylation, preventing translation?
eEF-2 is the site where Pseudomonas and Diphtheria toxins work.
How can you differentiate vitamin K from vitamin C deficiency by bleeding time and PT levels?
Vitamin K deficiency has normal bleeding time and increased PT, and vitamin C deficiency has increased bleeding time and normal PT.
What are the two actions of calcitonin?
It increases Ca2+ excretion from the kidney and increases bone mineralization.
What is a triplet repeat expansion? Mention an example
Protein is longer than normal and unstable. Ex. Huntington CAG repeat codes multiple glutamines; also Fragile-X
What is the term for chemicals that keep the pH constant despite the formation of acids and bases during metabolism?
Buffers (remember that buffers are best when they are used in a pH range near its pK)
What is the term for vitamin D deficiency prior to epiphyseal fusion?
Rickets prior to fusion, osteomalacia if the deficiency occurs after epiphyseal fusion.
How many ATPs per glucose are generated in glycolysis?
38 ATPs if aerobic, 2 ATPs if anaerobic (36 ATPs[malate shuttle] + 4 ATPs[Glycolysis] - 2 ATPs[phosphorylate glucose] = 38 ATPs)
FADH2 is produced in this reaction of oxidative phosphorylation
Succinate + FAD + succinate DH (complex II) --> fumarate + FADH2
Is the coding or the template strand of DNA identical to mRNA (excluding the T/U difference)?
The coding strand is identical to mRNA, and the template strand is complementary and antiparallel.
What are the vitamin K–dependent coagulation factors?
Factors II, VII, IX, X, and proteins C and S
Would a G-C or an A-T rich dsDNA sequence have a higher melting point? Why?
G-C rich sequences, because they have 3 hydrogen bonds, where A-T has 2 hydrogen bonds, resulting in higher melting points.
How many high-energy bonds are used to activate an AA?
2 ATPs, via the amino acyl tRNA synthase enzyme
How many codons code for AAs? How many for termination of translation?
61 codons code for AAs and 3 codons (UAA, UGA, UAG) code for the termination of translation.
What does a high Km mean? Low Km?
High Km = low affinity; low Km = high affinity
If a sample of DNA has 30% T, what is the percent of C?
Solved as 30% T + 30% A = 60%; therefore, C + G = 40%; then C = 20% and G = 20% (example of Chargaff's rule)
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