Bio Chem Exam 3

Front 1

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

A) electrophoresis – a gentle low-voltage gradient draws the DNA into the cell.

B) infection with a bacteriophage that carries the plasmid.

C) transformation

D) microinjection.

E) mixing plasmids with an extract of broken cells

Back 1

C) transformation

Front 2

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

A) A) Many make staggered (off-center) cuts within their recognition sequences.

B) They cleave and ligate DNA.

C) They are part of a bacterial defense system in which foreign DNA is cleaved.

D) They cleave DNA only at recognition sequences specific to a given restriction enzyme.

E) Some cut DNA to generate blunt ends.

Back 2

B) They cleave and ligate DNA.

Front 3

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

A) A) a number of conveniently located recognition sites for restriction enzymes.

B) a replication origin, which permits it to replicate autonomously.

C) resistance to two different antibiotics, which permits rapid screening for recombinant plasmids containing foreign DNA.

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) small overall size, which facilitates entry of the plasmid into host cells.

Back 3

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.

Front 4

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

A) A) DNA amplified by PCR can be cloned.

B) The boundaries of the amplified DNA segment are determined by the synthetic oligonucleotides used to prime DNA synthesis.

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

D) The technique is sufficiently sensitive that DNA sequences can be amplified from a single animal or human hair.

E) Newly synthesized DNA must be heat-denatured before the next round of DNA synthesis begins.

Back 4

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

Front 5

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

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

B) direct binding of a Gal4p activation domain to a DNA sequence in the promoter region.

C) having a promoter that responds directly to one of the two proteins whose interactions is being measured.

D) hybridization of DNA segments corresponding to the two genes being examined.

activation of DNA polymerase by the nearby binding of hybridizing protein complexes.

Back 5

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

Front 6

Biological waxes are all:

A) trimesters of glycerol and three long-chain saturated fatty acids.

B) trimesters of glycerol and palmitic acid.

C) sorcerers of single fatty acids with long-chain alcohols.

D) semesters of sphingolipids.

E) none of the above.

F) all of the above.

Back 6

E) none of the above.

Front 7

Which of the following is true of sphingolipids?

A) Phosphatidylcholine is a typical sphingolipid.

B) They always contain glycerol and fatty acids.

C) They contain two esterified fatty acids.

D) Cerebrosides and gangliosides are sphingolipids.

E) They may be charged, but are never amphipathic

Back 7

D) Cerebrosides and gangliosides are sphingolipids

Front 8

Which of the following statements about sterols is true?

A) Stigmasterol is the principal sterol in fungi.

B) Sterols are found in the membranes of all living cells.

C) Sterols are soluble in water, but less so in organic solvents such as chloroform.

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

E) The principal sterol of animal cells is ergosterol.

Back 8

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

Front 9

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

A) arachidonic acid.

B) testosterone.

C) vitamin A (retinol).

D) phosphatidylinositol.

E) ceramide.

Back 9

D) phosphatidylinositol.

Front 10

Which vitamin is derived from cholesterol?

A) A

B) C

C) D

D) P

E) Q

F) P

G) N

Back 10

C) D

Front 11

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

A) The domains that protrude on the cytoplasmic face of the plasma membrane nearly always have covalently attached oligosaccharides.

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

C) They can be removed from the membrane with high salt or mild denaturing agents.

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 are unusually susceptible to degradation by trypsin.

Back 11

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

Front 12

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

A) Individual lipid molecules in one face (monolayer) of the bilayer readily diffuse (flip-flop) to the other monolayer.

B) Polar, but uncharged, compounds readily diffuse across the bilayer.

C) The polar head groups face inward toward the inside of the bilayer.

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

E) The bilayer is stabilized by covalent bonds between neighboring phospholipid molecules.

Back 12

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

Front 13

The fluidity of a lipid bilayer will be increased by:

A) decreasing the number of unsaturated fatty acids.

C) increasing the temperature.

D) increasing the length of the alkyl chains.

B) decreasing the temperature.

E) substituting 18:0 (stearic acid) in place of 18:2 (linoleic acid).

Back 13

C) increasing the temperature.

Front 14

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

A) Location of receptor molecules

B) Structure of receptor molecules

C) Interactions between receptor and signal molecules

D) Transmembrane transport of signal molecules by receptor molecules

E) Structure of signal molecules

Back 14

D) Transmembrane transport of signal molecules by receptor molecules

Front 15

Which of the following statements concerning receptor enzymes is correct?

A) They are not usually membrane-associated proteins.

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

C) They have a ligand-binding site on the cytosolic side of the membrane.

D) They contain an enzyme activity that acts upon the extracellular ligand.

E) They have an active site on the extracellular side of the membrane.

Back 15

C) They have a ligand-binding site on the cytosolic side of the membrane

Front 16

Protein kinase A (PKA) is:

A) activated by covalent binding of cyclic AMP.

B) affected by cyclic AMP only under unusual circumstances.

C) allosterically activated by cyclic AMP.

D) noncompetitively inhibited by cyclic AMP.

E) competitively inhibited by cyclic AMP.

Back 16

C) allosterically activated by cyclic AMP.

Front 17

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

A) A) Cyclic AMP synthesis

B) GTP-binding protein

C) Protein kinase A

D) GTP hydrolysis

E) All of the above are involved.

Back 17

E) All of the above are involved.

Front 18

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

A) phosphatidyl glycerol + inositol + phosphate.

B) diacylglycerol + inositol + phosphate.

C) glycerol + inositol + phosphate.

D) diacylglycerol + inositol triphosphate.

E) glycerol + phosphoserine.

Back 18

D) diacylglycerol + inositol triphosphate.

Front 19

The specificity of signaling pathways includes all of the following except:

a. phosphorylation of target proteins at Ser, Thr, or Tyr residues.

b. migration of signal proteins into membrane rafts.

c. the ability to be switched off instantly by hydrolysis of a single phosphate-ester bond.

d. the assembly of large multiprotein complexes.

e. flippase-catalyzed movement of phospholipids from the inner to the outer leaflet.

Back 19

e. flippase-catalyzed movement of phospholipids from the inner to the outer leaflet.

Front 20

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

A) Activation of the receptor protein kinase activity results in the activation of additional protein kinases.

B) The substrates of the receptor protein kinase activity are only proteins that regulate transcription.

C) Binding of insulin to the receptor results in a change in its quaternary structure.

D) The receptor protein kinase activity is specific for tyrosine residues on the substrate proteins.

E) Binding of insulin to the receptor activates a protein kinase.

Back 20

B) The substrates of the receptor protein kinase activity are only proteins that regulate transcription.