Exam 2
What is a riboswitch?
A region of the mRNA that alters the structure upon binding of a ligand, thus altering translation.
What is a signal sequence?
A short amino acid sequence that targets a protein for transport across a specific membrane.
The covalent attachment of amino acids to tRNA molecules is performed by...
Aminoacyl tRNA synthetases
How can the cell contain an inheritable "memory" without changes in the DNA sequence?
Based on DNA methylation patterns.
How do intracellular membrane vesicles find the correct membrane to fuse with?
Based on the v-SNARE and t-SNARE system.
You are attempting to express a human extracellular protein in E. coli, but despite using a DNA sequence from which the introns have been removed, the protein produced by E. coli is not functional. What could be the reason for this?
Because E. coli does not perform protein glycosylation, and this is needed for the function of the protein.
Proteins that function in the thylakoid space of plant chloroplasts usually contain two consecutive (and distinct) signal sequences. Why?
Because these proteins need to be transported across two distinct membranes.
How does a gel shift assay work?
Binding of a protein to a DNA fragment alters the position of this DNA fragment in an agarose gel.
How can a transmembrane alpha-helix be predicted based on the amino acid sequence of a protein?
By calculating a hydropathy plot.
What experiment can distinguish a positive regulator of gene expression from a negative regulator of gene expression?
By measuring if the gene is a mutant lacking the regulatory protein.
What type of experiment can reveal the activity of a specific promoter region of the DNA in different regions of the embryo during development?
By staining the embryo for beta-galactosidase activity using anembryo in which the LacZ gene encoding beta-galactosidase was placed under the control of the promoter region of interest.
The formation of new vesicles from the plasma membrane (for endocytosis) and for transport between the ER, Golgi, an plasma membranes are all initiated through the formation of...
Coated vesicles.
The release of neurotransmitters into the synaptic cleft between two neuronal cells occurs through...
Exocytosis.
Cholesterol is transported through the blood stream as part of the...
Low density lipoprotein particle.
For the disposal of phagocytic vesicles containing bacteria, these vesicles usually proceed to fuse with the membrane of the...
Lysosome.
The uptake of cholesterol particles by cells is an example of...
Receptor-mediated endocytosis.
In bacteria, RNA polymerase itself does not recognize promoters. Instead, RNA bacterial polymerase forms a complex with a protein that helps recognize the promoter. This protein is...
Sigma factor
How can the Lac repressor prevent RNA polymerase from initiating transcription of the Lac operon?
The binding site of the Lac repressor overlaps with the promoter sequence.
How does the cell achieve the specific glycosylation of the extracellular regions of transmembrane proteins in the plasma membrane?
The extracellular regions of proteins are first exposed to the lumen of the ER and the Golgi, where they are glycosylated.
The composition on the lipids in the two leaflets of a biological membrane can be chemically distinct because...
The flop-flop process in which a lipid diffuses from one leaflet of the lipid bilayer to the other leaflet is very slow.
How does the cell achieve co-translational translocation across the membrane for proteins targeted for the endoplasmic reticulum?
The signal recognition particle pauses protein translation until the robisome is docked on a protein pore.
Why do many transcription factors contain a functionally important alpha-helix?
This alpha-helix makes specific molecular contacts with the exposed atoms in the base of the major groove.
How is processed mRNA transported across the nuclear envelope into the cytosol?
Through nuclear pores.
How can the protein composition in the part of the membrane of epithelial cells exposed to the gut be different for the part of the membrane on the opposite side of the cells?
Tight junctions prevent diffusion of membrane proteins between these two compartments of the plasma membrane.
The formation of peptide bonds during translation is catalyzed by...
rRNA.