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Mark the correct answer. Addition of phospholipids to newly synthesized membranes:
A. Are added directly to the various membranes at diverse cellular locations.
B. Asymmetry in membrane phospholipids occurs only during the addition of the new
membranes in the ER.
C. The ribosomes on the RER are associated with the production of the newly
synthesized phospholipids.
*D. Are added to cytoplasmic side of the RER membrane.
Which of these bind the SRP?
A. Tubulin
*B. EGF-R
C. Actin
D. Cop I
E. Clathrin
In a genetic sequence a yeast mutant was isolated in which proteins normally secreted
accumulated in the cytosol. The mutated protein is? Mark the correct answer:
A. Cop I
*B. Sec 61
C. M-6-P
D. Clathrin
Choose the correct statement:
A. Mitochondrial proteins that were synthesized with a signal peptide are always
maternally inherited
B. The genetic code of mitochondrial DNA is the same as that of bacteria
C. Most mitochondrial proteins are synthesized in the cytosol and transported into
mitochondria via the channel protein porin
*D. Protein import into the mitochondria requires energy in the form of both ATP and an
electrochemical potential.
The signal peptide of the insulin receptor:
*A. Cleaved in the lumen of the rough endoplasmic reticulum
B. Directs dynthesis of insulin receptor to cytoplasm
C. Present in cytosolic portion of molecule
D. Cleaved in lumen of the golgi apparatus
Mark the correct statement:
A. The higher the energetic requirements of a cell are, the more developed are the cristae
of the mitochondria in order to increase the number of signal peptide sites.
B. Though mitochondria may acquire different shapes, they are immobile structures
always found at the same cellular site.
C. The fact that mitochondria are surrounded by two membranes helps protect the
mitochondrial DNA from mutations.
*D. The higher the energetic requirements of a cell are, the more developed are the
cristae of the mitochondria in order to increase the surface area of the inner membrane.
The LDL binding sequence of the LDL receptor protein contains a cluster of negatively
charged amino acids. This region is important for:
A. Binding of uncoating heat shock protien.
B. Binding of protons in order to maintain endosomal acidic pH.
*C. Modulating ligand binding affinity in propotion to pH.
D. Recruiting lysosomal enzymes to break down the LDL receptor in the lysosome.
Microtubules undergo catastrophe and shrink when the GTP cap is removed because?
A. Degradation due to protease
B. Binding of tubulin-monomer with GDP at the + end
C. Dissociation of tubulin-GTP from the + end
*D. Bending of the tubulin-GDP protofilament
Which of these are intermediate fibers:
*A. Keratin
B. Lamin
Which is the correct statement? The centriole and basal body
A. Are composed of different cytoskeletal elements
B. Are both composed of Actin filaments and their associated proteins
C. Are both involved in cell division
*D. Are both composed of microtubules and their associated protein
Cytoskeleton. ATP is involved in several activities of the cytoskeleton. Which of the
following activities is independent of ATP binding?
*A. Growth of mictotubules
B. Growth of actin microfilaments
C. Transport of cargo along mictotubules
D. Transport of cargo along the microfilaments.
Mark the correct answer: A biopsy was taken from the skin of a patient suffering from
increased pigmentation. DNA anylysis of the biopsy has revealed the presence of a
mutation in the alpha subunit of the G protein Gs in the pigment producing cells. In view
of the fact that the hormone that stimulates pigmentation binds to a GPCR that is coupled
to Gs, you conclude that:
A. The mutation in Gs inhibits the ability of Gs to bind GTP
B. The mutation of Gs is a loss of function mutation
*C. The mutation in Gs inhibits its GTPase activity
D. No conclusions can be drawn based on these data
Mark the correct answer: The major role of tyrosine phosphorylation of growth factor
receptors is to:
A. Negatively regulate the receptors leading to their desensitization
B. Serve as docking sites for heterotrimeric G-proteins
C. Serve as docking sites for proteins that contain an SH3 domain.
*D. Serve as docking sites for proteins that contain an SH2 domain.
Mark the correct answer. Hydrolysis of inostol phospholipids leads to a rise in the
intracellular concentration of Ca2+ by:
A. producing DAG that mobilizes Ca2+ from the mitochondria
*B. producing IP3 that mobilizes Ca2+ from the mitochondria
C. producing DAG that binds it and opens plasma membrane localized Ca2+ channels
D. producing IP3 that directly activates PKC
Which of the following is NOT DIRECTLY involved in the separation of chromosomes
during anaphase?
A. Centromere
B. Kinetochore
*C. Astral Microtubules
D. Kinetochore Microtubules
A new yeast mutant was isolated. Yeast with this mutation divide slowly at 35°C and are
larger than wild type. The mutation is a(n):
A. inhibitory mutation of cdc 25 phosphatase
B. inhibitory mutation of wee1 kinase
C. mutation in COP1
D. mutation in mannose-6-phosphate receptor
E. mutation in clathrin
What is the arrow pointing at?
A. site of krebb's cycle
B. site of N-Glycosylation
*C. Site of oxidative phosphorylation
D. A coated Vessicle