BIO CHEM FROM BOOK Flashcards
Which of the following represents the most reduced form of carbon?
R-CH3 R-COOH R-CHO R-CH2OH CO2
R-CH3
The Km (Michaelis constant) of an enzyme for a substrate is defined operationally as
half the substrate concentration at which the reaction rate is maximal
the substrate concentration at which the reaction rate is half maximal
the dissociation constant of the enzymesubstrate complex
the dissociation constant of the enzymeproduct complex
the rate constant of the reaction at saturation
the substrate concentration at which the reaction rate is half maximal
Dinitrophenol (DNP) uncouples mitochondrial electron transport from oxidative phosphorylation by
dissipating the proton gradient
inhibiting cytochrome oxidase
dissociating the F0 and F1 units of the
ATP synthase complex
binding irreversibly to ubiquinone
blocking the adenine nucleotide carrier
(ATP/ADP exchanger)
dissipating the proton gradient (B) inhibiting cytochrome oxidase
Most of the dry mass in the trunk of a tree was originally derived from
the soil light energy amino acids CO2 glucose
the soil
Which of the following cell compartments is associated with a protein skeleton composed of lamins?
Chloroplast Basement membrane Mitochondrion Nucleus Peroxisome
Nucleus
Initiation of mitogenesis by epidermal growth factor and depolarization of the membrane of a skeletal muscle cell by acetylcholine are similar in that each
involves, as an essential early step, an ion flux across the plasma-membrane receptor of the responding cell
requires a ligand-mediated conformational change in a plasma-membrane receptor of the responding cell
requires activation of a G protein on the cytoplasmic face of the plasma membrane in the responding cell
is mediated by phosphorylation of the ligand receptor in the responding cell
completes its primary task by direct activation of specific regulatory DNA sequences in the
nucleus of the responding cell
is mediated by phosphorylation of the ligand receptor in the responding cell
The principal site of peptide neurohormone biosynthesis is the
nucleus rough endoplasmic reticulum dendrite postsynaptic density synaptic vesicle
rough endoplasmic reticulum
A previously unknown organism that lacks a nuclear membrane and mitochondria has just been discovered. Which of the following would this organism most likely possess?
Lysosomes Cilia Ribosomes Endoplasmic reticulum Chloroplasts
Cilia
Drugs that either stabilize or depolymerize microtubules can be used in cancer chemo- therapy. Which of the following is correct concerning such drugs?
They stimulate the immune system.
They prevent chromatin condensation.
They prevent movement of tumor cells into other tissues.
They interfere with mitosis.
They interfere with endocytosis.
They prevent movement of tumor cells into other tissues.
If the genetic code consisted of four bases per codon rather than three, the maximum number of unique amino acids that could be encoded would be
16 64 128 256 512
256
In humans, the Barr body is an
active X chromosome in females active X chromosome in males inactive Y chromosome in males inactive Y chromosome in females inactive X chromosome in females
inactive Y chromosome in females
Which of the following types of molecules is always found in virions?
Lipid Protein Carbohydrate DNA RNA
RNA
An RNA-dependent RNA polymerase is likely to be present in the virion of a
(A) DNA virus that multiplies in the cytoplasm
(B) DNA virus that multiplies in the nucleus
(C) minus-strand RNA virus
(D) plus-strand RNA virus
(E) transforming virus
DNA virus that multiplies in the nucleus
In E. coli, the inability of the lac repressor to bind an inducer would result in
no substantial synthesis of -galactosidase
constitutive synthesis of -galactosidase
inducible synthesis of -galactosidase
synthesis of inactive -galactosidase
synthesis of -galactosidase only in the absence of lactose
inducible synthesis of -galactosidase
If sucrose and monosodium glutamate (MSG) are added to a vinegar and oil salad dressing and shaken, the mixture will eventually separate into two phases of different density and polarity. Where will most of the sucrose and the MSG be located following phase separation?
Both will concentrate in the vinegar.
Both will concentrate in the oil.
Sucrose will concentrate in the oil and MSG will concentrate in the vinegar.
Sucrose will concentrate in the vinegar and MSG will concentrate in the oil.
Both will concentrate in the vinegar
A major advantage of monoclonal antibodies compared to polyclonal antibodies is that monoclonal antibodies
have identical binding sites that recognize a specific epitope
cross-link molecules that share antigenic sites
are more easily coupled with probes such as fluorescent dyes
have higher-affinity binding to antigens
can be produced against proteins that are immunogenic in rabbits
have identical binding sites that recognize a specific epitope
The initial product of photosynthetic CO2 fixation in C3 plants is
glyceraldehyde 3-phosphate dihydroxyacetone phosphate 3-phosphoglycerate phosphoenolpyruvate 1,3-bisphosphoglycerate
glyceraldehyde 3-phosphate
In which of the following systems is the entropy the greatest?
Water vapor
Liquid water at pH 7.0, 37°C
Water with sufficient acid added to lower the pH to 2.0
Supercooled water (liquid water at a temperature less than 0°C)
Ice
Water with sufficient acid added to lower the pH to 2.0
Which enzyme is activated by phosphorylation?
Acetyl-CoA carboxylase Fructose-1,6-bisphosphatase Glycogen synthase Pyruvate kinase Fructose-2,6-bisphosphatase
Acetyl-CoA carboxylase
All of the following statements about monomeric G proteins are true EXCEPT:
They are regulated by GTP-GDP exchange proteins.
They are regulated by GTPase activating proteins.
They regulate enzymes that synthesize cGMP.
They regulate vesicle formation.
They regulate vesicle fusion.
They regulate vesicle fusion.
All of the following are known to be part of a signal transduction cascade EXCEPT
phosphorylation of fibronectin
dissociation of the components of a heterotrimeric G-protein
enzymatic breakdown of phosphatidyl inositol bisphosphate (PIP2)
elevation of intracellular [Ca2+]
activation of cGMP phosphodiesterase
enzymatic breakdown of phosphatidyl inositol bisphosphate (PIP2)
Which of the following will result if the level of potassium ions in a solution bathing a nerve cell is raised tenfold while the cell is at its resting state?
The decrease in the normal K+ gradient will cause partial depolarization.
The amplification of the normal K+ gradient will cause partial hyperpolarization.
The added extracellular K+ will accelerate Na+/K+ pumping and cause partial depolarization.
The added extracellular K+ will cause ligand-gated ion channels to open.
The elevated K+ will promote Ca2+ channel opening and produce partial hyperpolarization
The decrease in the normal K+ gradient will cause partial depolarization.
SNARE proteins are found in the membranes of all of the following compartments EXCEPT
Mitochondria Golgi complex Early endosome Endoplasmic reticulum Synaptic plasma membrane
Mitochondria
Treatment of root tip meristem cells with the microtubule inhibitor colchicine results in all of the following EXCEPT
induction of polyploidy prevention of cytokinesis inhibition of mitotic spindle assembly cessation of DNA replication prevention of chromosome segregation
induction of polyploidy
- Genes a, b, and c are widely spaced in the bacterial genome. Transducing phage from an a+ b+ c+ bacterium were used to infect a culture of a− b− c− cells, and b+ transductants were selected. Which of the following best describes the predicted genotypes of these transductants?
Mostly a− b+ c− Mostly a− b+ c+ Mostly a+ b+ c+ Mostly a+ b+ c− a+ b+ c+ and a− b+ c− in equal frequencies
Mostly a+ b+ c−
If a cell has one chromosome in excess of the normal number of chromosomes present in the nucleus, it is referred to as
aneuploid polyploid tetraploid haploid allotetraploid
aneuploid
Which of the following statements about retrotransposons is correct?
They transpose via an RNA intermediate.
They contain genes for ribosomal proteins.
They possess a gene for RNA-dependent RNA polymerase.
They possess genes that encode proteins that integrate RNA into chromosomes.
They are found only in bacteria.
They transpose via an RNA intermediate
When bacteria produce mammalian proteins, cDNA is used rather than genomic DNA. Which of the following is the best explanation?
It is easier to clone cDNA than genomic DNA of comparable size.
It is easier to clone RNA than DNA.
It is not possible to clone the entire coding region of the gene.
Most eukaryotic genes have introns that cannot be removed in bacteria.
Most eukaryotic gene promoters do not function in bacteria.
It is easier to clone cDNA than genomic DNA of comparable size.
A mutation deleting an upstream activating sequence for a single gene would be expected to be
polar trans-dominant cis-dominant silent revertible
silent
The difference between the molecular weight of sucrose and that of the sum of the molecular weights of its components (glucose and fructose) is
0 1 16 18 180
16
Proline disrupts -helical structure in proteins because it is
an acidic amino acid an aromatic amino acid an imino acid a basic amino acid a sulfur-containing amino acid
an imino acid
Glycogen phosphorylase exists in two forms in skeletal muscle. The active form, phosphorylase a, is generated from phosphorylase b by
reversible dimerization of phosphorylase b, triggered by calcium ion
proteolytic cleavage of a decapeptide from the N-terminus of phosphorylase b
protonation of the active-site histidine residue by a decrease in intracellular pH
ATP-dependent phosphorylation of a specific serine residue on each subunit
noncovalent binding of ATP to allosteric sites on phosphorylase b
protonation of the active-site histidine residue by a decrease in intracellular pH
An alpha-helical conformation of a globular protein in solution is best determined by which of the following?
Ultraviolet-visible absorbance spectroscopy Fluorescence spectroscopy Electron microscopy Analytical ultracentrifugation Circular dichroism
Analytical ultracentrifugation
The nucleoside adenosine exists in a protonated form with a pKa of 3.8. The percentage of the protonated form at pH 4.8 is closest to
1 9 50 91 99
99
Membrane carrier proteins differ from membrane channel proteins by which of the following characteristics?
Carrier proteins are glycoproteins, while channel proteins are lipoproteins.
Carrier proteins transport molecules down their electrochemical gradient, while channel proteins transport molecules against their electrochemical gradient.
Carrier proteins can mediate active transport, while channel proteins cannot.
Carrier proteins do not bind to the material transported, while channel proteins do.
Carrier proteins are synthesized on free cytoplasmic ribosomes, while channel proteins are synthesized on ribosomes bound to the endoplasmic reticulum.
Carrier proteins transport molecules down their electrochemical gradient, while channel proteins transport molecules against their electrochemical gradient
Particular RNAs that are important for development are located in distinct regions of the Drosophila embryo. This is most directly demonstrated by using
western blotting northern blotting in situ hybridization in vitro translation electroporation
in situ hybridization
Which of the following events can induce a transient arrest in the translation of a secretory protein?
Binding of a polysome to an ER receptor
Binding of SRP to an N-terminal signal sequence
Binding of snRNPs to the large ribosomal subunit
Presence of a stop-transfer sequence in the polypeptide
Cleavage of the signal sequence by signal peptidase
Binding of snRNPs to the large ribosomal subunit
The common pathway of entry into the endoplasmic reticulum (ER) of secretory, lysosomal, and plasma membrane proteins is best explained by which of the following?
Binding of their mRNAs to a special class of ribosomes attached to the ER
Addition of a common sorting signal to each type of protein after completion of synthesis
Addition of oligosaccharides to all three types of proteins
Presence of a signal sequence that targets each type of protein to the ER during synthesis
Presence of a zinc finger-binding domain in these three types of proteins
Addition of a common sorting signal to each type of protein after completion of synthesis
Eukaryotic cells with DNA damage often cease progression through the cell cycle until the damage is repaired. This type of control over the cell cycle is referred to as
proteosome control damage control checkpoint control anticyclin control transcriptional control
anticyclin control
A microarray is a large collection of specific DNA oligonucleotides spotted in a defined pattern on a microscope slide. What is the most useful experiment that can be done with such a tool?
Predicting the presence of specific metabolites in a cell
Comparing newly synthesized nuclear RNA with cytoplasmic RNA to locate introns
Comparing RNA produced under two different physiological conditions to understand patterns of gene expression
Comparing proteins produced under two different physiological conditions to understand their function
Evaluating the linkage relationships of genes
Comparing RNA produced under two different physiological conditions to understand patterns of gene expression
In vertebrate genes, transcription regulatory regions that contain CpG islands are inactivated by which CpG modification?
Methylation Myristylation Phosphorylation Acetylation Ubiquitination
Phosphorylation
All of the following are proteins within the core nucleosome particle EXCEPT
H1 H2A H2B H3 H4
H1
In a study of arginine biosynthesis in yeast, four mutant haploids requiring arginine (Arg−) were isolated. The Arg− haploids were fused in pairwise combinations to form diploids, whose requirement for arginine was tested. The results of the tests were that all diploid combinations yielded arginine prototrophs. How many different Arg genes are represented among the four mutants?
One Two Three Four Five
One
A set of genes from Bacillus subtilis that encode the proteins required for sporulation have conserved DNA sequences −35 and −10 nucleotides before the site of transcript initiation, although the sequence at −35 is different from that seen in most other genes from that species. Which of the following best explains this difference?
A novel sigma factor is required for transcription initiation at these genes.
The −35 sequence is the binding site for a repressor of transcription.
The replication of these genes requires a specifically modified DNA polymerase.
Translation of the mRNAs transcribed from these genes requires specific ribosomes that recognize a modified Shine-Dalgarno sequence.
Transcription of these genes is induced by cAMP.
Translation of the mRNAs transcribed from these genes requires specific ribosomes that recognize a modified Shine-Dalgarno sequence.
Acetyl CoA, the cytoplasmic substrate for fatty acid synthesis, is formed in mitochondria. The inner mitochondrial membrane is impermeable to acetyl CoA. Which of the following compounds is the form in which the carbon of acetyl CoA is transported to the cytoplasm?
Malate Acetate Citrate Pyruvate Glucose
T(°C) pKw
0 14.94 25 14.00
50 13.28
75 12.71
Malate
The ion product for liquid water, Kw, varies with temperature (T), as indicated by the change in pKw shown in the table above. The definition of neutrality is [H+] = [OH−]. Which of the following is the pH of water at neutrality at 50°C ?
- 35 (B) 6.64
- 00
- 40
- 28
7.00
Which of the following groups of enzymes are unique to the Calvin cycle?
Ribulose bisphosphate carboxylase, phosphoribulokinase, and sedoheptulose
1,7-bisphosphatase
Ribose 5-phosphate isomerase, epimerase, and aldolase
Glyceraldehyde 3-phosphate dehydrogenase, phosphofructokinase, and phosphoenolpyruvate carboxylase
Phosphoglycolate phosphatase, glycerol kinase, and serine synthetase
Sucrose synthase, hexokinase, and glucose
6-phosphate dehydrogenase
Ribose 5-phosphate isomerase, epimerase, and aldolase
Which of the following best describes the hyperchromicity of DNA?
The shift in UV absorbance to longer wavelengths upon denaturation
The shift in UV absorbance to shorter wavelengths upon hydrolysis
The shift in UV absorbance to longer wavelengths upon annealing (forming double strands)
The increase in absorbance at 260 nm upon annealing
The increase in absorbance at 260 nm upon denaturation
The shift in UV absorbance to longer wavelengths upon denaturation
Isopentenyl pyrophosphate is a precursor of which of the following?
I. Cholesterol
II. Farnesyl groups on proteins
III. Steroid hormones
I, II, and III
I, II, and III
Cytokinesis in animal cells is caused by
the sliding movements of a band of microtubules around the circumference of the cell
the contraction of a band of actin filaments around the circumference of the cell
the movement of the mitotic spindle fibers
endocytosis of the plasma membrane around the equator of the cell
fusion of cytoplasmic membrane vesicles at the equator of the cell
fusion of cytoplasmic membrane vesicles at the equator of the cell
The synthesis of mRNA’s that encode the proteins of eukaryotic ribosomes occurs in the
cytoplasm nuclear envelope nucleolus euchromatin heterochromatin
nuclear envelope
Which of the following is NOT a consequence of increased cellular levels of cAMP?
Activation of a kinase cascade
Activation of the transducin G-protein
Increased phosphorylation of glycogen phosphorylase
Inhibition of glycogen synthesis
Dissociation of the cAMP-dependent protein kinase tetramer
Inhibition of glycogen synthesis
The KDEL sequence, found on luminal proteins of the ER, is responsible for
translocation of proteins into the ER lumen
insertion of proteins into the membrane of the ER
quality control in the ER
recognition by signal peptidase of the signal sequence
retrieval of ER luminal proteins from the Golgi
insertion of proteins into the membrane of the ER
Cyclins are proteins involved in regulation of
cell-cycle protein kinases
circadian rhythms
synthesis of cAMP
membrane circulation via exocytosis and endocytosis
the cycling of tubulin subunits through microtubules
the cycling of tubulin subunits through microtubules
The uppermost figure above shows the locations of four genes on the genetic map of an organism; the lower figure shows the locations of the same four genes on a physical map derived from the nucleotide sequence of the DNA of that organism. The maps are not identical because
there is no relationship between the position of genes in a genetic map and their positions on the DNA
recombination frequencies per kb of DNA are not uniform throughout a chromosome
the farther apart two genes are, the more likely they are to recombine
the closer two genes are, the more likely they are to recombine
some genes contain introns
recombination frequencies per kb of DNA are not uniform throughout a chromosome
