Biochem 3

Question 1

A common cloning strategy for introducing foreign genes into plants with Agrobacterium employs all the following features except:

Select one:

a. a shuttle vector with 25 bp T-DNA repeats flanking the foreign gene of choice.
b. a Ti plasmid lacking its T-DNA segment.
c. active vir gene products from the altered Ti plasmid.
d. a selectable antibiotic marker such as kanamycin resistance.

Answer 1

a. a shuttle vector with 25 bp T-DNA repeats flanking the foreign gene of choice.

Question 2

An example of a glycerophospholipid that is involved in cell signaling is:

Select one:

a. ceramide.
b. phosphatidylinositol.
c. arachidonic acid.
d. testosterone.
e. vitamin A (retinol).

Answer 2

b. phosphatidylinositol.

Question 3

Biological waxes are all:

Select one:

a. none of the above.
b. semesters of sphingolipids.
c. trimesters of glycerol and three long-chain saturated fatty acids.
d. esters of single fatty acids with long-chain alcohols.
e. trimesters of glycerol and palmitic acid.

Answer 3

d. esters of single fatty acids with long-chain alcohols.

Question 4

Hormone-activated phospholipase C can convert phosphatidylinositol 4,5-bisphosphate to:

Select one:

a. glycerol + inositol + phosphate.
b. diacylglycerol + inositol + phosphate.
c. diacylglycerol + inositol triphosphate.
d. glycerol + phosphoserine.
e. phosphatidyl glycerol + inositol + phosphate.

Answer 4

c. diacylglycerol + inositol triphosphate.

Question 5

Identify the molecule(s) derived from sterols.

Select one:

a. Gangliosides
b. Prostaglandins
c. Phosphatidylglycerol
d. Arachidonic acid
e. Vitamin D

Answer 5

e. Vitamin D

Question 6

In genetic engineering, in vitro packaging is used to:

Select one:

a. cut a desired region out of the host bacterium’s chromosome.
b. splice a desired gene into a plasmid.
c. place an antibiotic resistance gene in a plasmid.
d. ensure that genetically engineered bacteria are not accidentally released into the environment.
e. incorporate recombinant DNA into infectious bacteriophage particles.

Answer 6

e. incorporate recombinant DNA into infectious bacteriophage particles.

Question 7

In the laboratory, recombinant plasmids are commonly introduced into bacterial cells by:

Select one:

a. transformation-heat shock of the cells incubated with plasmid DNA in the presence of CaCl2.
b. electrophoresis - a gentle low-voltage gradient draws the DNA into the cell.
c. infection with a bacteriophage that carries the plasmid.
d. microinjection.
e. mixing plasmids with an extract of broken cells.

Answer 7

a. transformation-heat shock of the cells incubated with plasmid DNA in the presence of CaCl2.

Question 8

Programmed cell death is called:

Select one:

a. ubiquitination.
b. mitotic termination.
c. metastasis.
d. apoptosis.
e. oncogenic transformation.

Answer 8

d. apoptosis.

Question 9

Protein kinase A (PKA) is:

Select one:

a. affected by cyclic AMP only under unusual circumstances.
b. allosterically activated by cyclic AMP.
c. activated by covalent binding of cyclic AMP.
d. competitively inhibited by cyclic AMP.
e. noncompetitively inhibited by cyclic AMP.

Answer 9

b. allosterically activated by cyclic AMP.

Question 10

Proto-oncogenes can be transformed to oncogenes by all of the following mechanisms except:

Select one:

a. chromosomal rearrangements.
b. elimination of their start signals for translation.
c. chemically induced mutagenesis.
d. during a viral infection cycle.
e. radiation-induced mutation.

Answer 10

b. elimination of their start signals for translation.

Question 11

Steroid hormones are carried on specific carrier proteins because the hormones:

Select one:

a. need them in order to pass through the plasma membrane.
b. require subsequent binding to specific receptor proteins in the nucleus.
c. cannot find their target cells without them.
d. cannot dissolve readily in the blood because they are too hydrophobic.
e. are too unstable to survive in the blood on their own.

Answer 11

d. cannot dissolve readily in the blood because they are too hydrophobic.

Question 12

The biological role of restriction enzymes is to:

Select one:

a. restrict the size of DNA in certain bacteria.
b. degrade foreign DNA that enters a bacterium.
c. restrict the damage to DNA by ultraviolet light.
d. make bacteria resistant to antibiotics.
e. aid recombinant DNA research.

Answer 12

b. degrade foreign DNA that enters a bacterium.

Question 13

The E. coli recombinant plasmid pBR322 has been widely utilized in genetic engineering experiments. pBR322 has all of the following features except:

Select one:

a. a number of conveniently located recognition sites for restriction enzymes.
b. small overall size, which facilitates entry of the plasmid into host cells.
c. a replication origin, which permits it to replicate autonomously.
d. a number of palindromic sequences near the EcoRI site, which permit the plasmid to assume a conformation that protects newly inserted DNA from nuclease degradation.
e. resistance to two different antibiotics, which permits rapid screening for recombinant plasmids containing foreign DNA.

Answer 13

d. a number of palindromic sequences near the EcoRI site, which permit the plasmid to assume a conformation that protects newly inserted DNA from nuclease degradation.

Question 14

The G-protein involved in visual signal transduction is:

Select one:

a. rhodopsin.
b. a leukotriene.
c. arrestin.
d. a GTP receptor.
e. transducin

Answer 14

e. transducin.

Question 15

The inner (plasma) membrane of E. coli is about 75% lipid and 25% protein by weight. How many molecules of membrane lipid are there for each molecule of protein? (Assume that the average protein is Mr 50,000 and the average lipid is 750.)

Select one:

a. 50
b. 1
c. 50,000
d. 10,000
e. 200

Answer 15

200

Question 16

The PCR reaction mixture does not include:

Select one:

a. all four deoxynucleoside triphosphates.
b. DNA containing the sequence to be amplified.
c. DNA ligase.
d. heat-stable DNA polymerase.
e. oligonucleotide primer(s).

Answer 16

c. DNA ligase.

Question 17

The technique known as two hybrid analysis for detecting interacting gene products depends on:

Select one:

a. stimulation of transcription by interaction of two Gal4p domains via fused protein sequences.
b. hybridization of DNA segments corresponding to the two genes being examined.
c. having a promoter that responds directly to one of the two proteins whose interactions is being measured.
d. activation of DNA polymerase by the nearby binding of hybridizing protein complexes.
e. direct binding of a Gal4p activation domain to a DNA sequence in the promoter region.

Answer 17

a. stimulation of transcription by interaction of two Gal4p domains via fused protein sequences.

Question 18

Which of the following contains an ether-linked alkyl group?

Select one:

a. Gangliosides
b. Phosphatidyl serine
c. Platelet-activating factor
d. Sphingomyelin
e. Cerebrosides

Answer 18

c. Platelet-activating factor

Question 19

Which of the following does not involve cyclic AMP?

Select one:

a. Regulation of glycogen synthesis and breakdown
b. Regulation of glycolysis
c. Signaling by epinephrine
d. Signaling by glucagon
e. Signaling by acetylcholine

Answer 19

e. Signaling by acetylcholine

Question 20

Which of the following is not involved in signal transduction by the beta-adrenergic receptor pathway?

Select one:

a. GTP-binding protein
b. Protein kinase A
c. GTP hydrolysis
d. Cyclic AMP synthesis
e. All of the above are involved.

Answer 20

e. All of the above are involved.

Question 21

Which of the following is not involved in the specificity of signal transduction?

Select one:

a. Structure of signal molecules
b. Structure of receptor molecules
c. Interactions between receptor and signal molecules
d. Transmembrane transport of signal molecules by receptor molecules
e. Location of receptor molecules

Answer 21

d. Transmembrane transport of signal molecules by receptor molecules

Question 22

Which of the following is not true of sterols?

Select one:

a. They have a structure that includes four fused rings.
b. They are precursors of steroid hormones.
c. They are commonly found in bacterial membranes.
d. They are more common in plasma membranes than in intracellular membranes (mitochondria, lysosomes, etc.).
e. Cholesterol is a sterol that is commonly found in mammals.

Answer 22

c. They are commonly found in bacterial membranes.

Question 23

Which of the following is true of sphingolipids?

Select one:

a. Phosphatidylcholine is a typical sphingolipid.
b. They contain two esterified fatty acids.
c. Cerebrosides and gangliosides are sphingolipids.
d. They always contain glycerol and fatty acids.
e. They may be charged, but are never amphipathic.

Answer 23

c. Cerebrosides and gangliosides are sphingolipids.

Question 24

Which of the following statements about sterols is true?

Select one:

a. Sterols are found in the membranes of all living cells.
b. All sterols share a fused-ring structure with four rings.
c. Sterols are soluble in water, but less so in organic solvents such as chloroform.
d. Stigmasterol is the principal sterol in fungi.
e. The principal sterol of animal cells is ergosterol

Answer 24

b. All sterols share a fused-ring structure with four rings.

Question 25

Which of the following statements about the polymerase chain reaction (PCR) is false?

Select one:

a. DNA is amplified at many points within a cellular genome.
b. Newly synthesized DNA must be heat-denatured before the next round of DNA synthesis begins.
c. The technique is sufficiently sensitive that DNA sequences can be amplified from a single animal or human hair.
d. DNA amplified by PCR can be cloned.
e. The boundaries of the amplified DNA segment are determined by the synthetic oligonucleotides used to prime DNA synthesis.

Answer 25

a. DNA is amplified at many points within a cellular genome.

Question 26

Which of the following statements about type II restriction enzymes is false?

Select one:

a. They are part of a bacterial defense system in which foreign DNA is cleaved.
b. They cleave and ligate DNA.
c. Many make staggered (off-center) cuts within their recognition sequences.
d. Some cut DNA to generate blunt ends.
e. They cleave DNA only at recognition sequences specific to a given restriction enzyme

Answer 26

b. They cleave and ligate DNA.

Question 27

Which of the following statements concerning cyclins is not correct?

Select one:

a. They are activated and degraded during the cell cycle.
b. They are regulatory subunits for enzymes that catalyze the phosphorylation of proteins.
c. They can become linked to ubiquitin.
d. They contain specific amino acid sequences that target them for proteolysis.
e. They catalyze the phosphorylation of proteins

Answer 27

e. They catalyze the phosphorylation of proteins.

Question 28

Which of the following statements concerning receptor enzymes is correct?

Select one:

a. They are not usually membrane-associated proteins.
b. They have a ligand-binding site on the cytosolic side of the membrane.
c. They contain an enzyme activity that acts upon a cytosolic substrate.
d. They have an active site on the extracellular side of the membrane.
e. They contain an enzyme activity that acts upon the extracellular ligand

Answer 28

c. They contain an enzyme activity that acts upon a cytosolic substrate.

Question 29

Which of the following statements concerning signal transduction by the insulin receptor is not correct?

Select one:

a. Binding of insulin to the receptor results in a change in its quaternary structure.
b. The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription.
c. Binding of insulin to the receptor activates a protein kinase.
d. The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins.
e. Activation of the receptor protein kinase activity results in the activation of additional protein kinases.

Answer 29

b. The substrates of the receptor protein kinase activity are mainly proteins that regulate transcription.

Question 30

Which of these is a general feature of the lipid bilayer in all biological membranes?

Select one:

a. Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.
b. Polar, but uncharged, compounds readily diffuse across the bilayer.
c. The polar head groups face inward toward the inside of the bilayer.
d. The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.
e. Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer.

Answer 30

a. Individual lipid molecules are free to diffuse laterally in the surface of the bilayer.

Question 31

Which of these statements is generally true of integral membrane proteins?

Select one:

a. The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides.
b. They are unusually susceptible to degradation by trypsin.
c. A hydropathy plot reveals one or more regions with a high hydropathy index.
d. They undergo constant rotational motion that moves a given domain from the outer face of a membrane to the inner face and then back to the outer.
e. They can be removed from the membrane with high salt or mild denaturing agents.

Answer 31

c. A hydropathy plot reveals one or more regions with a high hydropathy index.

Question 32

Which one of the following signaling mechanisms is used most predominantly in plants?

Select one:

a. Cyclic-nucleotide dependent protein kinases
b. Protein tyrosine kinases
c. G protein-coupled receptors
d. Protein serine/threonine kinases
e. DNA-binding nuclear steroid receptors

Answer 32

d. Protein serine/threonine kinases