Usmle Biochemistry

Front 1

What are the three posttranscriptional modifications?

Back 1

1. 7-methyl guanine cap on the 5' end
2. Addition of the poly(A) tail to the 3' end
3. Removal of introns

Front 2

What AA is the major carrier of nitrogen byproducts from most tissues in the body?

Back 2

Glutamine

Front 3

What two AAs have a pKa of 4?

Back 3

Aspartic acid and glutamic acid

Front 4

How many acetyl CoAs per glucose enter into the TCA cycle?

Back 4

2 acetyl CoA per glucose, producing 12 ATPs per acetyl CoA, resulting in a total of 24 ATPs produced from glucose (via acetyl CoA) enter the TCA cycle

Front 5

What topoisomerase makes ssDNA cuts, requires no ATP, relaxes supercoils, and acts as the swivel in front of the replication fork?

Back 5

Topoisomerase I (Relaxase)

Front 6

In prokaryotes, what is the name of the RNA sequence that ribosomes bind to so translation can occur?

Back 6

Shine-Dalgarno sequence

Front 7

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 unaffected adults?

Back 7

Autosomal recessive

Front 8

What factors are needed for translation in prokaryotes?

Back 8

Elongation factor-G and GTP

Front 9

What three AAs must patients with maple syrup urine disease not eat?

Back 9

Isoleucine, leucine, and valine

Front 10

How many high-energy bonds are used to activate an AA?

Back 10

2 ATPs, via the amino acyl tRNA synthase enzyme

Front 11

What water-soluble vitamin deficiency results in pellagra?

Back 11

Niacin (B3)

Front 12

What glycolytic enzyme has a high Vmax, high Km, and low affinity for glucose?

Back 12

Glucokinase

Front 13

How many ATPs are generated per acetyl coenzyme A (CoA)?

Back 13

12 ATPs per acetyl CoA that enter the tricarboxylic acid (TCA) cycle (Krebs cycle)

Front 14

What cytoplasmic pathway produces NADPH and is a source of ribose 5-phosphate?

Back 14

HMP shunt

Front 15

What is the main inhibitor of pyruvate dehydrogenase?

Back 15

Acetyl CoA (pyruvate to acetyl CoA)

Front 16

Where on the codon and anticodon does the wobble hypothesis take place?

Back 16

3'end of the codon (third position) on mRNA and 5' end of the anticodon (first position) on tRNA.

Front 17

What DNA excision and repair enzyme is deficient in patients with xeroderma pigmentosum?

Back 17

Excision endonuclease, which removes thiamine dimers from DNA

Front 18

What form of bilirubin is carried on albumin?

Back 18

Unconjugated (indirect)

Front 19

What are the two ketogenic AAs?

Back 19

Leucine and lysine

Front 20

Which organisms have polycistronic mRNA?

Back 20

Prokaryotes. Polycistronic and prokaryotes both start with P.

Front 21

As what compound do the carbons for fatty acid synthesis leave the mitochondria?

Back 21

Citrate, via the citrate shuttle

Front 22

What four substances increase the rate of gluconeogenesis?

Back 22

1. Glucagon
2. NADH
3. Acetyl CoA
4. ATP

Front 23

With what three enzymes is thiamin pyrophosphate (TPP) associated?

Back 23

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

Front 24

What test uses very small amounts of DNA that can be amplified and analyzed without the use of Southern blotting or cloning?

Back 24

PCR

Front 25

What apoprotein is required for the release of chylomicrons from the epithelial cells into the lymphatics?

Back 25

apo B-48

Front 26

What enzyme catalyzes the covalent bonding of the AA's carboxyl group to the 3' end of tRNA?

Back 26

Aminoacyl-tRNA synthetase, which uses 2 ATPs for this reaction.

Front 27

What must be supplemented in patients with medium-chain acyl CoA dehydrogenase (MCAD) deficiency?

Back 27

Short-chain fatty acids

Front 28

What form of AA is found only in collagen?

Back 28

Hydroxyproline

Front 29

In a diabetic patient, to what does aldose reductase convert glucose?

Back 29

Sorbitol (resulting in cataracts)

Front 30

What enzyme catalyzes the rate-limiting step in cholesterol metabolism?

Back 30

HMG-CoA reductase

Front 31

What is the term for the pH at which the structure carries no charge?

Back 31

pI (isoelectric point)

Front 32

What enzyme catalyzes the rate-limiting step in gluconeogenesis?

Back 32

Fructose-1, 6-bisphosphatase

Front 33

What is the drug of choice in treating a patient with hyperuricemia due to underexcretion of uric acid?

Back 33

Probenecid, a uricosuric agent

Front 34

What enzyme deficiency results in darkening of the urine when exposed to air?

Back 34

Homogentisate oxidase deficiency is seen in patients with alcaptonuria.

Front 35

In eukaryotes, what transcription factor binds to the TATA box before RNA polymerase II can bind?

Back 35

Transcription factor IID

Front 36

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?

Back 36

Primase

Front 37

What enzyme catalyzes the rate-limiting step in fatty acid synthesis?

Back 37

Acetyl CoA carboxylase

Front 38

Name the eukaryotic DNA polymerase based on the following information:
• Replicates mitochondrial DNA

Back 38

DNA polymerase-γ

Front 39

Name the eukaryotic DNA polymerase based on the following information:
• Synthesizes the lagging strand during replication

Back 39

DNA polymerase-α

Front 40

Name the eukaryotic DNA polymerase based on the following information:
• Synthesizes the leading strand during replication

Back 40

DNA polymerase-δ

Front 41

What is the order of fuel use in a prolonged fast?

Back 41

1. Glucose from liver glycogen
2. Glucose from gluconeogenesis
3. Body protein
4. Body fat

Front 42

Which way will the O2 dissociation curve shift with the addition of 2, 3-bisphosphoglycerate (2, 3-BPG) to adult hemoglobin (Hgb)?

Back 42

Shifts it to the right

Front 43

What enzyme of pyrimidine synthesis is inhibited by the following?
• 5-FU

Back 43

Thymidylate synthase

Front 44

What enzyme of pyrimidine synthesis is inhibited by the following?
• Methotrexate

Back 44

Dihydrofolate reductase

Front 45

What enzyme of pyrimidine synthesis is inhibited by the following?
• Hydroxyurea

Back 45

Ribonucleotide reductase

Front 46

What is found in the R group if the AA is acidic? Basic?

Back 46

If a carboxyl group is the R group, it is acidic; if an amino group is the R group, it is said to be basic.

Front 47

What gluconeogenic mitochondrial enzyme requires biotin?

Back 47

Pyruvate carboxylase

Front 48

What factors are needed for translocation in eukaryotes?

Back 48

EF-2 and GTP

Front 49

DNA replication occurs during what phase of the cell cycle?

Back 49

S phase

Front 50

What is the end product of purine catabolism?

Back 50

Uric acid

Front 51

What causes transcription to stop in eukaryotes?

Back 51

The poly(A) site on the DNA

Front 52

What enzyme of the TCA cycle catalyzes the production of the following:
• FADH2

Back 52

Succinate dehydrogenase

Front 53

What enzyme of the TCA cycle catalyzes the production of the following:
• GTP

Back 53

Succinyl CoA synthetase

Front 54

What enzyme of the TCA cycle catalyzes the production of the following:
• NADH (hint: 3 enzymes)

Back 54

Isocitrate dehydrogenase, α-ketoglutarate dehydrogenase, and malate dehydrogenase

Front 55

What form of alcohol causes blindness?

Back 55

Methanol (wood alcohol)

Front 56

How many base pairs upstream is the prokaryotic TATA box promoter?

Back 56

There are two bacterial promoter regions upstream. The TATA box is - 10 base pairs upstream, and the -35 promoter site is self-explanatory.

Front 57

What are the two essential fatty acids?

Back 57

Linoleic acid and linolenic acid

Front 58

During a prolonged fast, why is the brain unable to use fatty acids?

Back 58

Fatty acids cannot cross the blood-brain barrier; therefore, they cannot be used as an energy source.

Front 59

What type of jaundice is seen in Rotor's syndrome?

Back 59

Conjugated (direct) hyperbilirubinemia

Front 60

If a sample of DNA has 30% T, what is the percent of C?

Back 60

Solved as 30% T + 30% A = 60%; therefore, C + G = 40%; then C = 20% and G = 20% (example of Chargaff's rule)

Front 61

From where is the energy for gluconeogenesis derived?

Back 61

β-Oxidation of fatty acids

Front 62

Name the type of mutation:
• The deletion or addition of a base

Back 62

Frameshift

Front 63

Name the type of mutation:
New codon specifies a different AA

Back 63

Missense

Front 64

Name the type of mutation:
• Unequal crossover in meiosis with loss of protein function

Back 64

Large segment deletions

Front 65

Name the type of mutation:
• New codon specifies for the same AA

Back 65

Silent

Front 66

Name the type of mutation:
• New codon specifies for a stop codon

Back 66

Nonsense

Front 67

What form of bilirubin can cross the blood-brain barrier?

Back 67

Unconjugated free bilirubin

Front 68

What AA is broken down into N2O, causing an increase in cyclic guanosine monophosphate (cGMP) of smooth muscle, hence vasodilation?

Back 68

Arginine

Front 69

What three things are needed to produce a double bond in a fatty acid chain in the endoplasmic reticulum?

Back 69

NADPH, O2, and cytochrome b5

Front 70

What are the vitamin K–dependent coagulation factors?

Back 70

Factors II, VII, IX, X, and proteins C and S

Front 71

Is the hydroxyl (–OH) end of DNA and RNA at the 3' or the 5' end?

Back 71

3' end. Phosphate (PO4) is at the 5' end.

Front 72

How many codons code for AAs? How many for termination of translation?

Back 72

61 codons code for AAs and 3 codons (UAA, UGA, UAG) code for the termination of translation.

Front 73

What is the enzyme for the oxidative reaction in glycolysis?

Back 73

Glyceraldehyde dehydrogenase

Front 74

What substrate builds up in Tay-Sachs disease?

Back 74

GM2 ganglioside

Caused by a deficiency of β-hexosaminidase A

Front 75

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?

Back 75

Mitochondrial inheritance

Front 76

What is the rate-limiting enzyme of glycogen synthesis?

Back 76

Glycogen synthase

Front 77

What sphingolipid is formed by the union of serine and palmitoyl CoA?

Back 77

Sphingosine

Front 78

What causes an increase in bone mineralization and Ca2+ along with PO4- absorption from the GI tract and kidney tubules?

Back 78

Vitamin D

Front 79

What two sugars can be used to produce cerebrosides?

Back 79

Glucose and galactose

Front 80

What group of eukaryotic regulatory proteins has a major factor in controlling the gene expression embryonically?

Back 80

Homeodomain proteins

Front 81

What causes the lysis of RBCs by oxidizing agents in a G-6-PD deficiency?

Back 81

The lack of glutathione peroxidase activity results in a decrease in NADPH production, leaving glutathione in the reduced state.

Front 82

All AAs have titration plateaus at what pH values?

Back 82

pH of 2 and 9

Front 83

What cytoplasmic organelle carries the enzymes for elongation and desaturation of fatty acyl CoA?

Back 83

SER

Front 84

What is the binding site for RNA polymerase?

Back 84

The promoter indicates where transcription will begin.

Front 85

What vitamin is necessary for epithelial health?

Back 85

Vitamin A is responsible for vision and epithelial health.

Front 86

What lipoprotein is formed if an IDL particle acquires cholesterol from a HDL particle?

Back 86

LDL

Front 87

What structure of a protein describes the interaction among subunits?

Back 87

Quaternary structure

Front 88

What is the only factor of enzyme kinetics that the enzyme affects?

Back 88

Ea (activation energy)

Front 89

Is the Lac operon activated or inactivated in the presence of both glucose and lactose?

Back 89

Inactivated; glucose results in decreased cAMP levels and therefore blocks protein binding between cAMP and CAP.

Front 90

At the end of each round of β-oxidation, what is released?

Back 90

Acetyl CoA, FADH2, and NADH

Front 91

What is the rate-limiting enzyme on glycolysis?

Back 91

Phosphofructokinase-1 and costs 1 ATP

Front 92

What enzyme of heme synthesis is deficient in the autosomal dominant disorder acute intermittent porphyria?

Back 92

Uroporphyrinogen-I synthase

Front 93

What enzyme is blocked by disulfiram?

Back 93

Aldehyde dehydrogenase

Front 94

Deficiencies in what enzyme result in insoluble glycogen synthesis formation?

Back 94

α-1, 6 transferase

Front 95

What eukaryotic translation enzyme is associated with the following:
• Initiation

Back 95

eIF-2 in the P site

Front 96

What eukaryotic translation enzyme is associated with the following:
• Elongation

Back 96

eEF-1

Front 97

What eukaryotic translation enzyme is associated with the following:
• Termination

Back 97

No enzymes are needed. When the stop codon reaches the A site, it results in termination.

Front 98

What AA undergoes N-glycosylation?

Back 98

Asparagine

Front 99

What is the pyrimidine intermediate that joins PRPP (5-Phosphoribosyl-1-Pyrophosphate)?

Back 99

Orotic acid
(purine metabolism)

Front 100

What intermediate of cholesterol synthesis anchors proteins in the membranes and forms CoA?

Back 100

Farnesyl pyrophosphate (FPP)

Front 101

What AA is a phenol?

Back 101

Tyrosine

Front 102

What hormone is activated in adipose tissue when blood glucose levels decrease?

Back 102

Hormone-sensitive lipase

Front 103

How many NADPHs are used per addition of acetyl CoA into a fatty acid chain?

Back 103

2 NADPHs per acetyl CoA

Front 104

What factors are needed for elongation in eukaryotes?

Back 104

EF-1 and GTP

Front 105

What purine base is contained in inosine monophosphate?

Back 105

Hypoxanthine (remember, IMP is a precursor for AMP and GMP)

Front 106

What are the two ways that nitrogen can enter into the urea cycle?

Back 106

Aspartate and carbomoyl PO4-

Front 107

What two requirements must be met for the Lac operon to be activated?

Back 107

Lactose must be present and glucose must be absent

Front 108

Name the phase of the eukaryotic cell cycle:
• Period of cellular growth (translation and transcription) before DNA synthesis

Back 108

G1 phase (gap 1)

Front 109

Name the phase of the eukaryotic cell cycle:
• Period of cellular growth (translation and transcription) after DNA synthesis

Back 109

G2 phase (gap 2)

Front 110

Name the phase of the eukaryotic cell cycle:
• Period of DNA replication (preparing for mitosis)

Back 110

S phase

Front 111

Name the phase of the eukaryotic cell cycle:
• Cells cease replicating (i.e., nerve cell)

Back 111

G0 phase

Front 112

True or false? RBCs anaerobically use glucose in both the well-fed and fasting states.

Back 112

True. Remember, RBCs do not contain mitochondria, so they cannot metabolize aerobically.

Front 113

What enzyme of the TCA cycle catalyzes the substrate level phosphorylation?

Back 113

Succinyl CoA synthetase

Front 114

What apoprotein on HDL activates lecithin–cholesterol acyltransferase (LCAT)?

Back 114

apo A-1

Front 115

What three AAs are used to synthesize the purine ring?

Back 115

1. Glycine
2. Aspartate
3. Glutamine

Front 116

How many ATPs are produced from cytoplasmic NADH oxidation using the glycerol phosphate shuttle?

Back 116

2 ATPs by oxidative phosphorylation

Front 117

What enzyme is deficient in patients with PKU?

Back 117

Phenylalanine hydroxylase

Front 118

What three steps of the TCA cycle generate NADH?

Back 118

1. Malate dehydrogenase
2. Isocitrate dehydrogenase
3. α-Ketoglutarate dehydrogenase

Front 119

What two enzymes of heme synthesis are inhibited by lead?

Back 119

ALA dehydrogenase and ferrochelatase

Front 120

What enzyme, induced by insulin and activated by apo C-II, is required for chylomicron and VLDL metabolism?

Back 120

Lipoprotein lipase

Front 121

What is the most common genetic deficiency resulting in hemolytic anemia?

Back 121

G-6-PD deficiency; pyruvate kinase deficiency is second.

Front 122

Are the following conditions associated with a negative or positive nitrogen balance?
• AA deficiency

Back 122

Negative

Front 123

Are the following conditions associated with a negative or positive nitrogen balance?
• Growth

Back 123

Positive

Front 124

Are the following conditions associated with a negative or positive nitrogen balance?
• Pregnancy

Back 124

Positive

Front 125

Are the following conditions associated with a negative or positive nitrogen balance?
• Uncontrolled DM

Back 125

Negative

Front 126

Are the following conditions associated with a negative or positive nitrogen balance?
• Starvation

Back 126

Negative

Front 127

Are the following conditions associated with a negative or positive nitrogen balance?
• Infection

Back 127

Negative

Front 128

Are the following conditions associated with a negative or positive nitrogen balance?
• Recovery from injury

Back 128

Positive

Front 129

Are the following conditions associated with a negative or positive nitrogen balance?
• Kwashiorkor

Back 129

Negative

Front 130

Why is the liver unable to metabolize ketone bodies?

Back 130

Hepatocytes lack the enzyme succinyl CoA acetoacetyl CoA transferase (thiophorase).

Front 131

What toxin ADP-ribosylates via Gs protein to increase cAMP?

Back 131

Cholera toxin

Front 132

What two vitamins are inactivated when they come in contact with acetaldehyde?

Back 132

Thiamine and folate

Front 133

Name the end product or products:
• Fatty acid synthesis

Back 133

Palmitate

Front 134

Name the end product or products:
• Fatty acid oxidation

Back 134

Acetyl CoA and propionyl CoA (in odd chain fatty acids)

Front 135

What is the term for production of a DNA copy from an RNA molecule?

Back 135

Reverse transcription

Front 136

What two monosaccharides are produced when lactose is hydrolyzed?

Back 136

Galactose and glucose

Front 137

What mineral is required for cross-linking of collagen molecules into fibrils?

Back 137

The enzyme lysyl oxidase requires Cu2+and O2 to function properly.

Front 138

What blotting technique uses the following for analysis?
• DNA

Back 138

Southern blot

Front 139

What blotting technique uses the following for analysis?
• Protein

Back 139

Western blot

Front 140

What blotting technique uses the following for analysis?
• RNA

Back 140

Northern blot

Front 141

How many high-energy bonds does the cycle of elongation cost?

Back 141

Four high energy bonds, two from ATP in AA activation and two from GTP

Front 142

What enzyme of purine synthesis is inhibited by allopurinol and 6-mercaptopurine?

Back 142

PRPP aminotransferase

Front 143

True or false? The urea cycle takes place in both the cytoplasm and the mitochondria.

Back 143

True. Remember, carbamoyl phosphate synthetase and ornithine transcarbamoylase are mitochondrial enzymes.

Front 144

What is the only fatty acid that is gluconeogenic?

Back 144

Propionic acid

Front 145

What enzyme has a 5' to 3' synthesis of the Okazaki fragments, 3' exonuclease activity, and 5' exonuclease activity?

Back 145

DNA polymerase I

Front 146

In what organelle does the TCA cycle occur?

Back 146

Mitochondria

Front 147

Do genomic or cDNA libraries contain introns, exons, promoters, enhancers, and are they fragmented?

Back 147

Genomic libraries are made from nuclear DNA, are fragmented, and contain all sequences found in the particular genome copied.

Front 148

What enzyme is deficient in selective T cell immunodeficiency?

Back 148

Purine nucleoside phosphorylase

Front 149

True or false? Adipose tissue lacks glycerol kinase.

Back 149

True. Adipose depends on glucose uptake for dihydroxyacetone phosphate (DHAP) production for triglyceride synthesis.

Front 150

In what form is excess folate stored in the body?

Back 150

N-5-methyl THF

Front 151

What is the term for taking an mRNA molecule and arranging the AA sequence forming a protein?

Back 151

Translation

Front 152

What enzyme is blocked by hydroxyurea?

Back 152

Ribonucleotide reductase

Front 153

What protein carries free fatty acids to the liver?

Back 153

Albumin

Front 154

What substrate is built up in Niemann-Pick disease?

Back 154

Sphingomyelin

Front 155

True or false? Methylation of bacterial DNA prevents restriction endonuclease from cutting its own chromosomes.

Back 155

True. Restriction endonucleases cut only unmethylated DNA.

Front 156

What two AAs have a pKa of 10?

Back 156

Lysine and tyrosine

Front 157

What is the only enzyme in the body that uses N-5-methyl folate?

Back 157

Homocysteine methyl transferase

Front 158

How can you differentiate vitamin K from vitamin C deficiency by bleeding time and PT levels?

Back 158

Vitamin K deficiency has normal bleeding time and increased PT, and vitamin C deficiency has increased bleeding time and normal PT.

Front 159

What is the term for a unit of DNA that encodes a particular protein or RNA molecule?

Back 159

A gene (a rather simple definition but accurate)

Front 160

Is the coding or the template strand of DNA identical to mRNA (excluding the T/U difference)?

Back 160

The coding strand is identical to mRNA, and the template strand is complementary and antiparallel.

Front 161

What enzyme is deficient in acute intermittent porphyria?

Back 161

porphobilinogen deaminase

Front 162

What five cofactors and coenzymes are required by pyruvate dehydrogenase?

Back 162

1. TTP
2. Lipoic acid
3. Coenzyme A from pantothenate
4. NAD(H) (from niacin or tryptophan)
5. FADH2 (from riboflavin)

Front 163

What pattern of genetic transmission affects only M and has no M-to-M transmission, and mother is usually an unaffected carrier?

Back 163

X-linked recessive

Front 164

To what does aldose reductase convert galactose?

Back 164

Galactitol

Front 165

Name three purine bases that are not found in nucleic acids.

Back 165

Xanthine, hypoxanthine, theophylline, theobromine, caffeine, and uric acid are all purines.

Front 166

What water-soluble-vitamin deficiency is associated with cheilosis and magenta tongue?

Back 166

Riboflavin (B2)

Front 167

What is the precursor of all sphingolipids?

Back 167

Ceramide

Front 168

What three substances stimulate glycogenolysis?

Back 168

1. Ca2+ : calmodulin ratio
2. Epinephrine
3. Glucagon

Front 169

What is the primer for the synthesis of the second strand in production of cDNA from mRNA?

Back 169

The hairpin loop made by reverse transcriptase at the 3' end of the first strand is the primer.

Front 170

What factors are needed for elongation in prokaryotes?

Back 170

EF-Tu or EF-ts and GTP

Front 171

What restriction endonuclease site is destroyed in sickle β-globin allele?

Back 171

MstII; changing codon 6 (from A to T) destroys the restriction site.

Front 172

What complex is needed for propionyl CoA carboxylase?

Back 172

Biotin, ATP, and CO2

Front 173

What enzyme catalyzes the reversible oxidative deamination of glutamate and produces the TCA cycle intermediate α-ketoglutarate?

Back 173

Glutamate dehydrogenase

Front 174

What enzyme is deficient in congenital erythropoietic porphyria?

Back 174

Uroporphyrinogen III cosynthase

Front 175

What is the drug of choice for treating a patient with hyperuricemia due to overproduction of uric acid?

Back 175

Allopurinol

Front 176

What is the maximum rate possible with a given amount of enzyme?

Back 176

Vmax

Front 177

From what do catalase, superoxide dismutase, and glutathione peroxidase defend the cell?

Back 177

Production of oxygen free radicals

Front 178

What signals are used to direct an enzyme to a lysosome?

Back 178

Phosphorylation of mannose residues

Front 179

What enzyme catalyzes the rate-limiting step of the urea cycle?

Back 179

Carbamoyl phosphate synthetase I

Front 180

What liver enzyme, for triglyceride synthesis, converts glycerol to glycerol-3-phosphate?

Back 180

Glycerol kinase

Front 181

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?

Back 181

Liver

Front 182

What pattern of inheritance does G-6-PD deficiency follow?

Back 182

X-linked recessive

Front 183

What is the term for conversion of a dsDNA molecule to the base sequence of an ssRNA molecule?

Back 183

Transcription (C comes before L in the alphabet, and transCription comes before transLation)

Front 184

Via what cell surface receptor does HDL cholesterol from the periphery enter hepatoceles?

Back 184

Scavenger receptor (SR-B1)

Front 185

Which shuttle is used to bring fatty acyl CoA from the cytoplasm for ketogenesis?

Back 185

Carnitine acyl CoA transferase II

Front 186

What enzyme is blocked by 5-FU?

Back 186

Thymidylate synthetase

Front 187

What disease has a genetically low level of UDPglucuronate transferase, resulting in elevated free unconjugated bilirubin?

Back 187

Gilbert's syndrome

Front 188

What AA has a pKa of 13?

Back 188

Arginine

Front 189

What X-linked recessive disorder is characterized by hyperuricemia, spastic cerebral palsy, mental retardation, and self-mutilation?

Back 189

Lesch-Nyhan syndrome

Front 190

How many ATPs per glucose are generated from glycolysis in RBCs?

Back 190

2 ATPs, because RBCs use only anaerobic metabolism.

Front 191

What enzyme catalyzes the rate-limiting step in glycogenolysis?

Back 191

Glycogen phosphorylase

Front 192

Would a G-C or an A-T rich dsDNA sequence have a higher melting point? Why?

Back 192

G-C rich sequences, because they have 3 hydrogen bonds, where A-T has 2 hydrogen bonds, resulting in higher melting points.

Front 193

As what AAs do muscles send nitrogen to the liver?

Back 193

Alanine and glutamine

Front 194

What sphingolipid cannot be produced without sialic acid and amino sugars?

Back 194

Ganglioside

Front 195

What happens to affinity if you increase Km?

Back 195

Affinity decreases; they are inversely proportional.

Front 196

What type of bilirubin is found in neonatal jaundice?

Back 196

Indirect or unconjugated

Front 197

What two AAs do not have more than one codon?

Back 197

Methionine (start) and tryptophan are the only two AAs with only one codon.

Front 198

What bonds are broken by exonucleases?

Back 198

External 3', 5' PDE bonds

Front 199

How can a genetic deficiency of carbamoyl phosphate synthetase be differentiated from an ornithine transcarbamoylase deficiency?

Back 199

Uracil and orotic acid levels increase with ornithine transcarbamoylase deficiency and are normal in carbamoyl phosphate synthetase deficiency.

Front 200

Name the lipoprotein based on the following characteristics.
• apo E

Back 200

IDL

Front 201

Name the lipoprotein based on the following characteristics.
• apo B-100

Back 201

LDL

Front 202

Name the lipoprotein based on the following characteristics.
• apo E, apo B-100, apo C-II

Back 202

VLDL

Front 203

Name the lipoprotein based on the following characteristics.
• apo A-1, apo E, apo C-II

Back 203

HDL

Front 204

Name the lipoprotein based on the following characteristics.
• apo E, apo C-II, apoB-48

Back 204

Chylomicrons

Front 205

True or false? There is no hormonal control to the TCA cycle.

Back 205

True. The energy status of the cell dictates if the cycle is running or relaxing.

Front 206

What are the three tissues where triacylglycerols are produced?

Back 206

1. Liver
2. Muscle
3. Adipose tissue

Front 207

What toxin ADP-ribosylates via Gi to increase cAMP?

Back 207

Pertussis toxin

Front 208

What enzyme catalyzes the rate-limiting step in heme synthesis?

Back 208

δ-ALA synthase

Front 209

What cycle is responsible for converting to glucose in the liver the lactate produced in the RBCs?

Back 209

Cori cycle

Front 210

What enzyme is used to remove the hairpin loop during production of cDNA from mRNA?

Back 210

S1 nuclease

Front 211

Does a saturated fatty acid have double bonds?

Back 211

No, unsaturated fatty acids have double bonds.

Front 212

What pyrimidine base is found
• Only in RNA?

Back 212

Uracil

Front 213

What pyrimidine base is found
• Only in DNA?

Back 213

Thymine

Front 214

What pyrimidine base is found
• In both DNA and RNA?

Back 214

Cytosine

Front 215

What two AAs require vitamin C for hydroxylation?

Back 215

Proline and lysine

Front 216

What is the only organ in the body that can produce ketone bodies?

Back 216

The liver (in the mitochondria)

Front 217

What determines the rate of reaction?

Back 217

The energy of activation

Front 218

What is the term for the number of trinucleotide repeats increasing with successive generations and correlating with increased severity of disease?

Back 218

Anticipation, associated with fragile X syndrome; Huntington's disease is also associated with a decrease in onset of age.

Front 219

What enzyme is blocked by methotrexate/ trimethoprim?

Back 219

Dihydrofolate reductase

Front 220

What fructose metabolism enzyme is deficient in patients with vomiting, apathy, diarrhea, jaundice, proximal renal tubular acidosis, hypoglycemia, and hyperuricemia?

Back 220

Aldolase B deficiencies are treated by eliminating fructose from the diet.

Front 221

What enzyme catalyzes the rate-limiting step in purine synthesis?

Back 221

PRPP aminotransferase

Front 222

What water-soluble-vitamin deficiency is associated with poor wound healing, easy bruising, bleeding gums, anemia, and painful glossitis?

Back 222

Vitamin C

Front 223

What three substrates control the enzyme PEPCK for the conversion of oxaloacetate (OAA) to pyruvate in the cytoplasm?

Back 223

1. Cortisol (stimulates PEPCK)
2. Glucagon
3. GTP

Front 224

What genetic defect is characterized by coarse facial features, gingival hyperplasia, macroglossia, psychomotor and growth retardation, club foot, claw hand, cardiorespiratory failure, and death in the first decade of life?

Back 224

I-cell disease is a result of a genetic defect affecting the phosphorylation of mannose residues.

Front 225

What two glycolytic enzymes catalyze the substrate-level phosphorylations?

Back 225

3-Phosphoglycerate kinase and pyruvate kinase; this produces two ATPs per enzyme (total four ATPs)

Front 226

What pathway uses HMG CoA synthetase in the cytoplasm?

Back 226

Cholesterol biosynthesis

Front 227

Where in the body is heme converted to bilirubin?

Back 227

RES(Reticular endothelial system)

Front 228

What protein is required by prokaryotic RNA polymerases to initiate transcription at the promoter region of DNA?

Back 228

Sigma factor

Front 229

What enzyme catalyzes the rate-limiting step in pyrimidine synthesis?

Back 229

Aspartate transcarbamylase

Front 230

What are the two actions of calcitonin?

Back 230

It increases Ca2+ excretion from the kidney and increases bone mineralization.

Front 231

What enzyme of the purine salvage pathway is deficient in the following?
• Selective T-cell immunodeficiency

Back 231

Purine nucleoside phosphorylase

Front 232

What enzyme of the purine salvage pathway is deficient in the following?
• SCID

Back 232

Adenosine deaminase

Front 233

What enzyme of the purine salvage pathway is deficient in the following?
• Lesch-Nyhan syndrome

Back 233

HGPRT

Front 234

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?

Back 234

Alanine cycle

Front 235

What is the primary end product of pyrimidine synthesis?

Back 235

UMP

Front 236

What pyrimidine base is produced by deaminating cytosine?

Back 236

Uracil

Front 237

What AA is classified as basic even though its pK is 6.5 to 7?

Back 237

Histidine, because of the imidazole ring found in the R group, is basic.

Front 238

What enzyme is deficient in hereditary protoporphyria?

Back 238

Ferrochelatase

Front 239

What elongation factor is inactivated by ADP ribosylation, preventing translation?

Back 239

eEF-2 is the site where Pseudomonas and Diphtheria toxins work.

Front 240

Is linolenic acid an omega-3 or omega-6 fatty acid?

Back 240

Omega-3; linoleic is omega-6

Front 241

How many ATPs per glucose are generated in glycolysis?

Back 241

38 ATPs if aerobic, 2 ATPs if anaerobic (36 ATPs[malate shuttle] + 4 ATPs[Glycolysis] - 2 ATPs[phosphorylate glucose] = 38 ATPs)

Front 242

Name the three ketone bodies.

Back 242

Acetoacetate, acetone, and β-hydroxybutyrate

Front 243

What three bases are pyrimidines?

Back 243

1. Cytosine
2. Uracil (only in RNA)
3. Thymidine

Front 244

Name the RNA subtype based on the following:
• The most abundant form of RNA in the cell

Back 244

rRNA

Front 245

Name the RNA subtype based on the following:
• Found only in the nucleus of eukaryotes and functions to remove introns from mRNA

Back 245

snRNA

Front 246

Name the RNA subtype based on the following:
• Only type of RNA that is translated

Back 246

mRNA

Front 247

Name the RNA subtype based on the following:
• Carries AA to the ribosome for protein synthesis

Back 247

tRNA

Front 248

Name the RNA subtype based on the following:
• RNA molecules with enzymatic activity

Back 248

Ribozymes

Front 249

Name the RNA subtype based on the following:
• Found only in the nucleus of eukaryotic cells and are precursors of mRNA

Back 249

hnRNA

Front 250

What enzyme is deficient in the following glycogen storage disease?
• von Gierke's disease

Back 250

Glucose-6-phosphatase

Front 251

What enzyme is deficient in the following glycogen storage disease?
• Pompe's disease

Back 251

Lysosomal α-1, 4-glucosidase

Front 252

What enzyme is deficient in the following glycogen storage disease?
• McArdle's disease

Back 252

Muscle glycogen phosphorylase

Front 253

What enzyme is deficient in the following glycogen storage disease?
• Hers' disease

Back 253

Hepatic glycogen phosphorylase

Front 254

In prokaryotes, what is the term for a set of structural genes that code for a select group of proteins and the regulatory elements required for the expression of such gene?

Back 254

Operon

Front 255

What are the two most common AAs found in histones?

Back 255

Lysine and arginine

Front 256

What five pathways use SAM (S-adenosylmethionine) as the methyl donor?

Back 256

1. Epinephrine synthesis
2. Phosphatidyl choline
3. Creatine
4. Methylation of cytosine
5. N-methyl cap of mRNA

Front 257

What complex of the ETC contains Cu2+?

Back 257

Complex 4

Front 258

How many ATPs per glucose are produced by pyruvate dehydrogenase?

Back 258

6 ATPs (remember 2 pyruvates per glucose are produced, and 2 NADHs result from production of acetyl CoA, so 6 ATPs)

Front 259

What is the size of the prokaryotic ribosome?

Back 259

70S ribosomes in prokaryotes and 80S ribosomes in eukaryotes

Front 260

What type of fatty acid is associated with a decrease in serum triglycerides and cardiovascular disease?

Back 260

Omega-3 fatty acids

Front 261

What disease is produced by a deficiency in the enzyme tyrosinase?

Back 261

Albinism. Tyrosine is converted to melanin by the enzyme tyrosinase.

Front 262

In what form are triglycerides sent to adipose tissue from the liver?

Back 262

VLDLs

Front 263

What determines the rate of a reaction?

Back 263

The energy of activation (Ea)

Front 264

What is the rate-limiting enzyme of the HMP shunt?

Back 264

G-6-PD

Front 265

What vitamin is necessary for the transfer of one amino group from a carbon skeleton to another?

Back 265

Pyridoxal phosphate is derived from vitamin B6 and is needed to transfer the amino groups of one carbon skeleton to another.

Front 266

What is the only sphingolipid that contains choline and PO4?

Back 266

Sphingomyelin (lecithin also, but it is not a sphingolipid)

Front 267

What protein catalyzes the formation of the last PDE bond between the Okazaki fragments to produce a continuous strand?

Back 267

DNA ligase

Front 268

What type of damage to the kidneys is caused by drinking ethylene glycol (antifreeze)?

Back 268

Nephrotoxic oxylate stones

Front 269

What water-soluble-vitamin deficiency may result from eating raw eggs?

Back 269

Biotin (only if eaten in large quantities)

Front 270

Regarding the Lac operon, for what do the following genes code?
• Z gene

Back 270

β-Galactosidase

Front 271

Regarding the Lac operon, for what do the following genes code?
• Y gene

Back 271

Galactoside permease

Front 272

Regarding the Lac operon, for what do the following genes code?
• I gene

Back 272

Lac repressor protein

Front 273

Regarding the Lac operon, for what do the following genes code?
• A gene

Back 273

Thiogalactoside transacetylase

Front 274

What attaches to protons and allows them to enter into the mitochondria without going through the ATP-generating system?

Back 274

2, 4-Dinitrophenol

Front 275

1-α-Hydroxylase activity is increased in response to what two physiologic states? (hint: think of vitamin D activity)

Back 275

Hypocalcemia and hypophosphatemia

Front 276

What is the major ketone body produced during alcoholic ketoacidosis?

Back 276

β-Hydroxybutyrate

Front 277

What enzyme catalyzes the rate-limiting step in the TCA cycle?

Back 277

Isocitrate dehydrogenase

Front 278

Name the pattern of genetic transmission characterized thus: both M and F are affected; M may transmit to M; each generation has at least one affected parent; and one mutant allele may produce the disease.

Back 278

Autosomal dominant

Front 279

What bonds are broken by endonucleases?

Back 279

Internal 3', 5' PDE bonds

Front 280

Name the GLUT transporter based on the following:
• Found in liver and pancreatic β-cells

Back 280

GLUT 2

Front 281

Name the GLUT transporter based on the following:
• Found in skeletal muscle and adipose tissues

Back 281

GLUT 4

Front 282

Name the GLUT transporter based on the following:
• Found in most tissues, including brain and RBCs

Back 282

GLUT 3 and 4

Front 283

What enzyme catalyzes the rate-limiting step in fatty acid oxidation?

Back 283

Carnitine acyltransferase-I

Front 284

What enzyme of the TCA cycle also acts as complex II of the ETC?

Back 284

Succinate dehydrogenase

Front 285

What is the term for chemicals that keep the pH constant despite the formation of acids and bases during metabolism?

Back 285

Buffers (remember that buffers are best when they are used in a pH range near its pK)

Front 286

In the mitochondria, what complex is needed for pyruvate carboxylase to catalyze the reaction from pyruvate to OAA?

Back 286

Biotin, ATP, and CO2

Front 287

How many ATPs are produced from cytoplasmic NADH oxidation using the malate shuttle?

Back 287

3 ATPs by oxidative phosphorylation

Front 288

What is the rate-limiting step of the following?
• Fatty acid synthesis

Back 288

Acetyl CoA carboxylase

Front 289

What is the rate-limiting step of the following?
• β-Oxidation

Back 289

Carnitine acyltransferase I

Front 290

What is the rate-limiting step of the following?
• Ketogenolysis

Back 290

HMG CoA synthase

Front 291

What is the rate-limiting step of the following?
• Cholesterol synthesis

Back 291

HMG CoA reductase

Front 292

What direction does RNA polymerase move along the template strand of DNA during transcription?

Back 292

3'-5' direction, synthesizing RNA in the 5'-3' direction

Front 293

True or false? Histidine activates the histidine operon.

Back 293

False. Histidine operon is activated when there are low intracellular levels of histidine.

Front 294

What organ is responsible for the elimination of excess nitrogen from the body?

Back 294

The kidneys excrete the excess nitrogen from the body as urea in the urine.

Front 295

What is the only way to increase maximum velocity (Vmax)?

Back 295

Increase enzyme concentrations

Front 296

Name the two purine bases found in both DNA and RNA.

Back 296

Adenine and guanine

Front 297

What prokaryotic positioning enzyme in translation is blocked by the following?
• Tetracycline

Back 297

EF-Tu and EF-Ts of the 30S ribosomal subunit

Front 298

What prokaryotic positioning enzyme in translation is blocked by the following?
• Erythromycin

Back 298

EF-G of the 50S subunit

Front 299

What prokaryotic positioning enzyme in translation is blocked by the following?
• Streptomycin

Back 299

IF-2 of the 30S subunit

Front 300

True or false? DNA polymerases can correct mistakes, whereas RNA polymerases lack this ability.

Back 300

True. DNA polymerases have 3'-5' exonuclease activity for proofreading.

Front 301

What are the two precursors of heme?

Back 301

Glycine and succinyl-CoA

Front 302

What two factors cause PTH to be secreted?

Back 302

A decrease in Ca2+ and an increase in PO4-

Front 303

What are the nonoxidative enzymes of the HMP shunt? Are the reactions they catalyze reversible or irreversible?

Back 303

Transketolase and transaldolase. The reactions they catalyze are reversible.

Front 304

What are the five AAs that are both ketogenic and glucogenic?

Back 304

Isoleucine, threonine, tryptophan, tyrosine, and phenylalanine

Front 305

What artificial sweetener must patients with PKU avoid?

Back 305

Aspartame

Front 306

Cri-du-chat syndrome results in a terminal deletion of the short arm of what chromosome?

Back 306

Chromosome 5

Front 307

What substrate gets built up in Gaucher's disease?

Back 307

Glucosyl cerebroside

Front 308

What protein prevents ssDNA from reannealing during DNA replication?

Back 308

Single-strand DNA binding protein

Front 309

What type of jaundice is seen in Dubin-Johnson syndrome?

Back 309

Conjugated (direct) hyperbilirubinemia, a transport defect

Front 310

What type of DNA library is made from the mRNA from a tissue expressing a particular gene?

Back 310

cDNA libraries are derived from mRNA, are continuous, and contain no introns or regulatory elements.

Front 311

What is the most common cause of vitamin B6 deficiency?

Back 311

Isoniazid treatment

Front 312

What lysosomal enzyme is deficient in
• Gaucher's disease?

Back 312

Glucocerebrosidase

Front 313

What lysosomal enzyme is deficient in
• Niemann-Pick disease?

Back 313

Sphingomyelinase

Front 314

What lysosomal enzyme is deficient in
• Tay-Sachs disease?

Back 314

Hexosaminidase A

Front 315

What are the three exceptions to the rule of codominant gene expression?

Back 315

Barr bodies in females, T-cell receptor loci, and immunoglobulin light and heavy chain loci

Front 316

How many kilocalories per gram are produced from the degradation of fat? CHO? Protein?

Back 316

9 kcal/g from fat metabolism; 4 kcal/g from both CHO and protein metabolism

Front 317

What is the only way to increase the Vmax of a reaction?

Back 317

Increase the concentration of enzymes

Front 318

From which two substances are phospholipids made?

Back 318

Diacylglycerols and phosphatidic acid

Front 319

What intermediate enables propionyl CoA to enter into the TCA cycle?

Back 319

Succinyl CoA

Front 320

What vitamin is an important component of rhodopsin?

Back 320

Vitamin A

Front 321

What is the term to describe the 5'-3' sequence of one strand being the same as the opposite 5'-3' strand?

Back 321

Palindrome

Front 322

What gluconeogenic enzyme is absent in muscle, accounting for its inability to use glycogen as a source for blood glucose?

Back 322

Glucose-6-phosphatase

Front 323

What is the term for vitamin D deficiency prior to epiphyseal fusion?

Back 323

Rickets prior to fusion, osteomalacia if the deficiency occurs after epiphyseal fusion.

Front 324

In what disease is there a genetic absence of UDP-glucuronate transferase, resulting in an increase in free unconjugated bilirubin?

Back 324

Crigler-Najjar syndrome

Front 325

What enzyme requires molybdenum as a cofactor?

Back 325

Xanthine oxidase

Front 326

At what three sites can the HMP shunt enter into glycolysis?

Back 326

1. Fructose-6-phosphate
2. Glucose-6-phosphate
3. Glyceraldehyde-3-phosphate

Front 327

What is the term for the pH range where the dissociation of H+ occurs?

Back 327

pK (think of it as where half is base and half is acid)

Front 328

What regulates the rate of ketone body formation?

Back 328

The rate of β-oxidation

Front 329

What are the eight liver-specific enzymes?

Back 329

1. Fructokinase
2. Glucokinase
3. Glycerol kinase
4. PEPCK
5. Pyruvate carboxylase
6. Galactokinase
7. Fructose-1, 6-bisphosphatase
8. Glucose-6-phosphatase

Front 330

How many bases upstream is the eukaryotic TATA box promoter?

Back 330

There are two eukaryotic upstream promoters. The TATA box is –25 base pairs upstream; the CAAT box is –75 bases upstream.

Front 331

What is needed to initiate translation?

Back 331

IF and GTP (eIF for eukaryotes)

Front 332

What part of the 30S ribosome binds to the Shine-Dalgarno sequence?

Back 332

16S subunit

Front 333

What component of the ETC is inhibited by the following?
• Barbiturates

Back 333

Complex I

Front 334

What component of the ETC is inhibited by the following?
• Antimycin A

Back 334

Cytochrome b/c1

Front 335

What component of the ETC is inhibited by the following?
• Cyanide

Back 335

Cytochrome a/a3

Front 336

What component of the ETC is inhibited by the following?
• Oligomycin

Back 336

Fo/F1 complex

Front 337

What component of the ETC is inhibited by the following?
• Atractyloside

Back 337

ATP/ADP Translocase

Front 338

What component of the ETC is inhibited by the following?
• CO

Back 338

Cytochrome a/a3

Front 339

What component of the ETC is inhibited by the following?
• Rotenone

Back 339

Complex I

Front 340

What component of the ETC is inhibited by the following?
• Azide

Back 340

Cytochrome a/a3

Front 341

What AA is a precursor of the following substances?
• Serotonin

Back 341

Tryptophan

Front 342

What AA is a precursor of the following substances?
• GABA

Back 342

Glutamate

Front 343

What AA is a precursor of the following substances?
• Histamine

Back 343

Histidine

Front 344

What AA is a precursor of the following substances?
• Creatine

Back 344

Glycine/arginine

Front 345

What AA is a precursor of the following substances?
• NAD

Back 345

Tryptophan

Front 346

What AA is a precursor of the following substances?
• N2O

Back 346

Arginine

Front 347

What two enzymes are vitamin B12-dependent

Back 347

Homocysteine methyl transferase and methylmalonyl CoA transferase

Front 348

What two post-transcriptional enzymes in collagen synthesis require ascorbic acid to function properly?

Back 348

Prolyl and lysyl hydroxylases

Front 349

What three organs participate in production of vitamin D?

Back 349

1. Skin
2. Liver
3. Kidney

Front 350

What water-soluble-vitamin deficiency is associated with neural tube defects in the fetus?

Back 350

Folic acid

Front 351

What phase of Interphase is haploid (N)?

Back 351

G1 phase; G2 and S phase are diploid (2N).

Front 352

What neurotransmitter inhibits the optic nerve bipolar cell and shuts off in response to light?

Back 352

Glutamate

Front 353

Which of the following—DNA methylating enzymes, scaffolding proteins, histone acetylases, or deacetylases—is a regulator of eukaryotic gene expression?

Back 353

Histone acetylases is a regulator favoring gene expression. All of the others favor inactivation.

Front 354

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 the disease.

Back 354

X-linked dominant

Front 355

What fat-soluble vitamin is connected to selenium metabolism?

Back 355

Vitamin E

Front 356

Why are eukaryotes unable to perform transcription and translation at the same time like prokaryotes?

Back 356

In eukaryotes transcription occurs in the nucleus and translation in the cytoplasm.

Front 357

What is determined by the secondary structure of an AA?

Back 357

The folding of an AA chain

Front 358

What three vitamin deficiencies are associated with homocystinemia?

Back 358

Folate, vitamin B12, and vitamin B6

Front 359

If the pH is more acidic than the pI, does the protein carry a net positive or net negative charge?

Back 359

When the pH is more acidic than the pI, it has a net positive charge, and when the pH is more basic than the pI, it has a net negative charge.

Front 360

What form of continuous DNA, used in cloning, has no introns or regulatory elements?

Back 360

cDNA, when it is made from mRNA

Front 361

What is the start codon, and what does it code for in eukaryotes? Prokaryotes?

Back 361

The one start codon, AUG, in eukaryotes codes for methionine and in prokaryotes formylmethionine.

Front 362

What parasite found in raw fish can produce vitamin B12 deficiency?

Back 362

Diphyllobothrium latum

Front 363

Methylating uracil produces what pyrimidine base?

Back 363

Thymine

Front 364

Name the eukaryotic RNA polymerase based on the following:
• Synthesizes tRNA, snRNA, and the 5S rRNA

Back 364

RNA polymerase III

Front 365

Name the eukaryotic RNA polymerase based on the following:
• Synthesizes hnRNA, mRNA, and snRNA

Back 365

RNA polymerase II

Front 366

Name the eukaryotic RNA polymerase based on the following:
• Synthesizes 28S, 18S and 5.8S rRNAs

Back 366

RNA polymerase I

Front 367

What is the primary screening test used to detect HIV-infected individuals? Confirmatory test?

Back 367

ELISA is used as a screening test because it is very sensitive; Western blot is used as a confirmatory test because it detects antibodies (protein) to the HIV virus.

Front 368

How many covalent bonds per purine-pyrimidine base pairing are broken during denaturation of dsDNA?

Back 368

None. Denaturation of dsDNA breaks hydrogen bonds, not covalent bonds.

Front 369

How many hydrogen bonds link A-T? C-G?

Back 369

A-T are linked by 2 hydrogen bonds, C-G by 3 hydrogen bonds.

Front 370

What DNA replication enzyme breaks the hydrogen bond of base pairing, forming two replication forks?

Back 370

Helicase (requires ATP for energy)