Quiz 6 Practice

How does miRNA inhibit translation?

• Associates with RISC and binds to mRNA

• Causes base pair mismatch and inhibits translation

• Inhibits translation by inhibiting eEF4A which unwinds mRNA

• Targets mRNA for degradation

When an adequate growth factor supply is present, how does eIF2 function?

• eIF2 carries MET to ribosome

• It must have GTP to carry out this process

• eIF2 carries LYS to the ribosome

• eIF2 carries LYS to the cytosol

What mediates the exchange of GDP for GTP in eIF2?

• eIF2B

• eIF4E

• 4E-BP

• Protein Kinase

What happens to eIF2 and EIF2B when stress or growth factor starvation is present?

• Protein kinase phosphorylates eIF2 and eIF2B

• Phosphorylation inhibits the exchange of GDP for GTP which inhibits translation

• The phosphate group serves a source of energy, powering translation

• Causes base pair mismatch

Which of the following apply to eIF4E?

• It facilitates ribosomal binding

• In the absence of growth factors, non-phosphorylated 4E-BP binds to EIF4E which inhibits translation

• In the presence of growth factors, PK phosphorylates 4E-BP which removes it from eIF4E, allowing translation to proceed.

• In the presence of growth factors, PK phosphorylates 4E-BP which removes it from eIF4E, which inhibits translation.

Which of the following apply to ferritin?

• Translation of ferritin is regulated by iron levels

• When iron levels are abundant, more ferritin will be synthesized

• When iron levels are low, IRP1 and 2 bind to 5' UTR of ferritin and block its translation

What is the importance of molecular chaperones?

• They facilitate the folding of other proteins

• Prevent incorrect folding of nascent polypeptides or chains that are still being translated on ribosomes

• Upregulate transcription and uses DNA looping to get in closer proximity to promoter

• Stabilize unfolded polypeptide chains during transport to avoid misfolding

Which of the following apply to protein misfolding?

• Leads to aggregation or insoluble fibers called amyloid fibers

• Accumulation of amyloid fibers causes Alzheimer's and Parkinson's

• Chaperones facilitate protein misfolding

What types of brain tissue is Alzheimer's characterized by?

• Amyloid plaques which are aggregates of misfolded amyloid-B-proteins

• Neurofibrillary tangles or misfolded tau

• Beta pleated sheets

• Alpha helices

What is the role of protein disulfide isomerase?

• Catalyzes disulfide bond formation

• Forms cysteine bonds in insulin

• Facilitates the addition of carbs to protein

• Adds glycine to N-terminal