MCB 252 Exam 3

What causes the power stroke for Myosin II? -Binding of ATP to the myosin head -Hydrolysis of ATP to ADP + Pi -Release of Pi from the myosin head -Release of ADP from the myosin head -As described in lecture, we do not yet know.

Release of Pi from the myosin head

Approximately how many different types of cells are found in the human body?

210

What is the distance that is equal to one full turn of an actin filament? -18 nm -36 nm -54 nm -72 nm -90 nm

72 nm

In lecture we discussed a version of the figure below. Which of the following comments is TRUE about the relationship between A and B in this figure? A--IB -A inhibits B -A negatively regulates B -in the absence of A, B functions. -A in habits and negatively regulates B -A negatively regulates B, and in the absence of A, B functions. -A inhibits and negatively regulates B, and in the absence of A, B functions.

A inhibits and negatively regulates B, and in the absence of A, B functions.

A. Is the data displayed in this figure collected from a single experiment in a single test tube, or does it need to be collected from multiple test tubes? B. Is this experiment measuring reactions that are at steady state or reactions that are undergoing net assembly (or disassembly)?

A. Multiple test tubes B. steady state

What are the two aspects of the critical concentration that were discussed in lecture that relate to whether or not actin filaments will form in a reaction and to reactions that contain both monomers and filaments when they reach equilibrium?

Actin filaments will only form if the concentration of g-actin is above the critical concentration. For reaction that contain both monomers and filaments, the concentration of monomers will be equal to the critical concentration.

Which of the following proteins nucleates the formation of branched actin filaments? -CapZ -formin -tropomodulin -cofilin -Arp2/3 complex

Arp 2/3 complex

Based on our discussion in lecture, which of the following statements are truant false? 1: Apoptosis can occur in response to cellular damage 2: Apoptosis can occur in response to normal developmental events -Statement 1 is TRUE, and statement 2 is FALSE. -Statement 1 is FALSE, and statement 2 is TRUE. -Both statements 1 and 2 are FALSE. -Both statements 1 and 2 are TRUE.

Both statements 1 and 2 are TRUE

As described in lecture, cells form actin filaments in particular regions of the cell in part because they nucleate filament formation at particular times and places within cells and in part because they inhibit the formation of filaments that are "randomly" nucleated. What protein(s) is/are responsible for inhibiting the elongation of filaments that are randomly nucleated? -Profilin -Thymosin B4 -Tropomodulin -Formin -CapZ

CapZ

The diagram below was discussed in lecture and represents the evolutionary history of a variety of human globin genes.

False: The alpha-globin gene indicated by the arrow is more closely related to the myoglobin gene than it is to the beta-globin gene indicated by the arrow.

What causes the Myosin II head to move to the cocked position? -Release of Pi from the myosin head -Release of ADP from the myosin head -Binding of ATP to the myosin head -Hydrolysis of ATP to ADP + Pi -As described in lecture, we do not yet know.

Hydrolysis of ATP to ADP + P

Which of the following statements is true? -Large proteins elute from a gel filtration column before small proteins. -Small proteins elute from a gel filtration column before large proteins.

Large proteins elute from a gel filtration column before small proteins.

Which of the following best describes the fate of the cloned DNA used in a transformation experiment? -The DNA remains on a plasmid and is maintained as an episome (non-chromosomal DNA) indefinitely. -The DNA is integrated into a chromosome and maintained indefinitely. -The DNA remains on a plasmid and is maintained as an episome (non-chromosomal DNA) for a day or two and is then lost. -The DNA is integrated into a chromosome but is degraded and lost after a day or two.

The DNA is integrated into a chromosome and maintained indefinitely.

In lecture we talked about mutant alleles of Cdc42, Rac and Rho that were constructed in vitro and used to reveal the role of these G-proteins in cell crawling. Were those in vitro constructed alleles dominant or recessive to the wild-type allele? -The alleles were dominant to the wild-type allele -The alleles were recessive to the wild-type allele

The alleles were dominant to eh wild-type allele

You have a solution of G-actin and AMPPNP. Initially your solution contains no filaments. You add Mg++ to your solution, wait five minutes and examine your reaction by electron microscopy. You find that there are now a substantial number of F-actin filaments. What can you conclude about the initial concentration of G-actin in your solution prior to the addition of Mg++? Which one of the following answers best fits your observations? -The initial concentration of G-actin was below the critical concentration. -The initial concentration of G-actin was at the critical concentration. -The initial concentration of G-actin was above the critical concentration

The initial concentration of G-actin was above the critical concentration

A polyclonal antibody contains many different antibodies which collectively recognize many different epitopes on an antigen. -True -False

True

As described in lecture, all three types of cytoskeletal filaments (actin filaments, intermediate filaments and microtubules) are multi-stranded. -True -False

True

As discussed in lecture, at least some types of cell movements are based on changes in cell shape. -True -False

True

As discussed in lecture, at one time or another virtually every amino acid on the surface of actin is thought to contact another protein. -True -False

True

As discussed in lecture, in an in vitro reaction, actin filaments assemble faster at the plus end than at the minus end. -True -False

True

As discussed in lecture, many aspects of development and tissue formation can be viewed as converting sheets of cells into tubes, balls, and tubular solid structures. -True -False

True

As discussed in lecture, metastasis of cancer cells is thought to involve an active process of cell migration. -True -Flase

True

Gene families are formed by gene duplication and divergence. -True -False

True

Some actin family members are subunits of some chromatin remodeling complexes. -True -False

True

TRUE or FALSE: Steady-state reactions require the continuous input of energy to remain at steady state. -True -False

True

We've talked extensively about the fact that actin polymerization can move the plasma membrane outward, away from the center of the cell. As discussed in lecture, actin polymerization can also be used in endocytosis to move vesicles from the plasma membrane toward the center of the cell. -True -False

True

When performing column chromatography to purify a protein of interest, one needs an assay to identify which fractions that contain the protein of interest. True or False: As discussed in lecture, we use a different assay for each different protein that we purify (For instance, the assay for protein A will be different than the assay for protein B which will be different than the assay for protein C, etc). -True -False

True

What is required for a steady state reaction that is not required for an equilibrium reaction?

continuous input of energy

Match the experimental approach with the corresponding experimental strategy. Approach: X = Biochemistry Y = Genetics Z = Cell biology Strategy: i = Watch the process in a microscope. Follow the dynamics of particular proteins in a living cell. Does inhibiting the function of a specific protein in a living cell block the process you are interested in? ii = Purify the proteins involved and study their behavior in vitro. Recapitulate the process in a test tube. iii = Isolate a mutant organism that is defective in the process.

X= ii, Y=iii, Z=i

Can ADP-actin monomers form F-actin polymers in the absence of ATP in vitro? Based on your answer to this question, what important property can be inferred about actin polymerization?

Yes, ADP-actin monomers can F-actin polymers in vitro in the absence of ATP. From this observation we can infer that the energy of ATP hydrolysis is not necessary for actin polymerization.

Which of the following is a downstream target of the Rac pathway? Choose the single best answer. - a formin family member -a WASP family member and the Arp2/3 complex -the Arp2/3 complex -a WASP family member -a WASP family member, the Arp2/3 complex, and a formin family member

a WASP family member and the Arp 2/3 complex

In lecture we discussed the use of speckle microscopy. What did the speckled microscopy experiment that we discussed actually show?

actin filaments treadmill in vivo

Which type of cells described in lecture are multipotent

adult stem cells

Some mutations that cause hypertrophic cardiomyopathy are in the gene that encodes cardiac myosin. As discussed in lecture, those mutations result in: - an increased force of cardiac contraction relative to wild-type myosin -a decreased force of cardiac contraction relative to wild-type myosin

an increased force of cardiac contraction relative to wild-type myosin

What is the name of the process by which cells undergo "programmed cell death"?

apoptosis

During protein purification, how does one determine which fractions contain the protein of interest?

can be done by carrying out an assay fro the protein of interst

What is the term for the fraction of the ATPase cycle in which a myosin head is bound to an actin filament? -duty cycle -binding fraction -dwell time -binding percentage -activated fraction

duty cycle

Which type of cells described in lecture are pluripotent?

embryonic stem cells

What are the three embryonic germ layers?

endoderm, ectoderm, mesoderm

Which of the following models of myosin V movement is thought to be correct? -jogging model -sliding model -super-charger model -inchworm model -hand over hand model

hand over hand model

Which drug results in loss of actin filaments? -phalloidin -destabilin -latrunculin

latrunculin

You wish to visualize the dynamics (movement of) two different proteins over time in a living tissue culture cell. Describe how you could achieve this goal.

make a gene fusion to two different color derivatives of GFP and transform/transfect then into you tissue sample. Visualize by fluorescence microscopy

Gel filtration chromatography separates proteins based on which physical or chemical property of the proteins?

molecular weight/size

Which drug stabilizes actin filaments? -phalloidin -cytochalasin -stabilin -latunculin

phalloidin

Myosin is a -plus end directed motor -minus end directed motor

plus end directed motor

Which end of actin filaments within sarcomeres is associated with (attached to) Z discs? -plus end for all actin filaments -minus end for all actin filaments -plus end on one end of a sarcomere and the minus end on the other end of a sarcomere

plus end for all actin filaments

In lecture we discussed a process that facilitates exon shuffling. Which of the following processes was that? -Transcription -Translation -DNA replication -splicing

splicing

In addition to an X-ray diffraction pattern, what other information is needed to generate a high-resolution three-dimensional structure of a protein?

the sequence of protein

As long as ATP is present in an in vitro actin assembly reaction that is at steady state, which of the following will be occurring? -treadmilling -assembly at the minus end -disassembly at the plus end -disassembly at the minus end -assembly at the plus end

treadmilling, disassembly at he minus end, assembly at the plus end

A step size that is a multiple of 36 nm allows myosin V to do what? -walk down one side of the actin filament -walk in both directions -walk as either a monomer or dimer -all of the above

walk down one side of the actin filament

Which technique allows the determination of the three-dimensional structure of a protein? -Ion exchange chromatography -Gel filtration chromatography -immuno-fluorescence microscopy -X-ray crystallography -genetics

x-ray crystallography