Download Quiz #4 1. Which of the following statements is

Quiz #4
1. Which of the following statements is true about Proteins A and B given that the two proteins
were run through a normal-phase HPLC system?
a.
b.
c.
d.
Protein A is more hydrophobic than Protein B.
Protein A is more hydrophilic than Protein B.
Protein A has a greater molecular weight than Protein B.
Protein A has more charged groups than Protein B.
Normal-phase chromatography has a polar stationary phase and a non-polar mobile phase,
resulting in more hydrophilic molecules eluting later. HPLC does not provide any direct
information about the molecular weight or number of charged groups. Therefore, Protein A
is more hydrophobic than Protein B.
2. True or false: the transmembrane domains of proteins that span the plasma membrane are
hydrophilic.
False – the transmembrane domain is primarily hydrophobic, allowing it to interact with the
hydrophobic region of the plasma membrane.
3. You treat a plate of cells that are actively producing and secreting Protein X with a toxin that
inhibits transport across the nuclear membrane. Which of the following is most likely to occur?
a. DNA for Protein X accumulates in the nucleus.
b. mRNA for Protein X accumulates in the nucleus.
c. Protein X accumulates in the nucleus.
d. Protein X accumulates in cytoplasmic vesicles.
Transcription (generation of mRNA from DNA) occurs in the nucleus, while translation
(generation of protein from mRNA) occurs in the cytoplasm (specifically, the endoplasmic
reticulum). Therefore, inhibiting nuclear transport will prevent the translocation of mRNA
into the cytoplasm, causing it to accumulate in the nucleus.
4. Which of the following statements is false regarding cellular trafficking of proteins?
a. Vesicles containing proteins targeted for extracellular secretion are said to be undergoing
the process of endocytosis.
b. The rough endoplasmic reticulum is the site of protein synthesis from mRNA. (true)
c. The Golgi apparatus is responsible for post-translational modifications of proteins. (true)
d. All of the above are true.
Answer a. is false because a correct statement would have read as follows: Vesicle
containing proteins targeted for extracellular secretion are said to be undergoing
exocytosis.
5. You have a peptide (MW 1,000 g/mol) and the full length protein (MW 50,000 g/mol) from
which it is derived in a mixture in solution (equal concentrations of each molecule). You place a
biomaterial in this solution. The contact angle of your material surface is 110 degrees. Which of
the following would most likely occur?
a. The peptide only would adsorb to the surface within seconds and remain there.
b. The protein only would adsorb to the surface within seconds and remain there.
c. The peptide would adsorb to the surface within seconds and then undergo exchange with
the protein.
d. The protein would adsorb to the surface within seconds and then undergo exchange with
the peptide.
Initial adsorption to the surface is mediated by diffusion, in which case a smaller molecule
will adsorb more quickly (larger diffusivity). As time passes, the larger protein that has a
greater affinity with the surface due to its size will undergo exchange and displace the
peptide, which has less interactions with the surface because it is smaller
6. What type of membrane protein is involved in cell contacts between the cell membrane and
fibronectin?
a. Selectins
b. Integrins
c. Cadherins
d. Cell adhesion molecules (CAMs)
Integrins are involved in cell-extracellular matrix interactions and fibronectin is a common
ECM component.