Chapter 11: Cell Communication
What happens to an active G protein for it to turn itself "off?"
The G protein hydrolyzes its bound GTP into GDP and inorganic phosphate (Pi), returning to an inactive state.
Which specific type of microtubules anchor the mitotic spindle to the plasma membrane, providing stability during chromosomal movement?
Astral microtubules (asters).
On what end are nucleotides added to a DNA/RNA primer.
3' end.
What is the chemical nature of the linkage that attaches the 5' GTP cap to the pre-mRNA, and what is its primary protective purpose?
It is a 5'-5' linkage that protects the mRNA from degradation and assists in ribosomal binding.
What is the structural and transcriptional difference between heterochromatin and euchromatin?
Heterochromatin is densely packed and usually not expressed, while euchromatin is loosely arranged and accessible for transcription.
In the yeast mating response, which two proteins are activated by the phosphorylation cascade to initiate the growth of "shmoo" microfilament projections?
Fus3 (which moves to the plasma membrane) and Formin.
What specific motor proteins are located at the kinetochore to "walk" the chromosome along the microtubule toward the spindle pole?
Dynein motor proteins.
What allows a prokaryote to synthesize it's DNA quickly?
Multiple origins or replications?
What enzyme turns an Uncharged tRNA to a Charged tRNA.
Aminoacyl tRNA synthetase.
Contrast the transcriptional effects of histone acetylation versus DNA methylation.
Histone acetylation loosens chromatin to promote transcription, while DNA methylation condenses chromatin to reduce transcription.
During sugar taste transduction on the tongue, which second messenger is responsible for opening the sodium channels that depolarize the sensory neuron?
Inositol triphosphate (IP3)
During the transition from the G2 phase to the M phase, what is the name of the active kinase complex that triggers the start of mitosis?
Maturation Promoting Factor (MPF).
Describe the trombone model of DNA replication.
It explains how leading and lagging strands are synthesized at the same time.
In what specific chemical direction is a polypeptide synthesized by the ribosome?
From the N-terminus (amino end) to the C-terminus (carboxyl end).
What allows cells to specifically express certain genes.
The presence of specific transcription factors within the cell.
Which signal protein(s) does Fight or Flight (epinephrine) use AND what is the cellular response?
GPCR, depolymerization of glycogen
Which enzyme is activated at the M checkpoint to degrade the cohesin proteins, allowing sister chromatids to separate?
Separase.
What enzyme removes RNA primers and replaces them with DNA.
DNA Polymerase I.
Name the sites and funcitonality of a Ribosome.
A site - charged tRNA enters
P site - holds growing protein
E site - tRNA exits
How does the degree of complementarity between a microRNA (miRNA) and its target mRNA determine the regulatory outcome?
If all bases are complementary, the mRNA is degraded; if the match is less complete, translation is blocked.
If a G protein is genetically modified so that it is physically incapable of exchanging GDP for GTP, what would happen to the cellular response stage?
There would be no cellular response.
Name the molecule and the process that allows the cell to degrade cyclin.
Ubiquitin and Ubiquination.
Why do Okazaki Fragments form?
They form as DNA can only be polymerized in the 5'->3' direction.
What occurs during the translation of a protein destined for the endomembrane system when the Signal-Recognition Particle (SRP) binds to the signal peptide?
Translation is temporarily stopped until the SRP/ribosome complex docks onto the receptor on the rough ER membrane.
What is the natural biological purpose of the CRISPR-Cas system in bacteria?
It serves as a genomic defense system against viruses (phages) that have already infected the bacteria.