15 bitches

Which of the following statements about the unfolded protein response (UPR) is false?

Activation of the UPR occurs when receptors in the cytoplasm sense misfolded proteins.

Which of the following statements is true?

Chaperone proteins in the mitochondria facilitate the movement of proteins across the outer and inner mitochondrial membranes.

Which of the following statements about vesicle budding from the Golgi is false?

Clathrin molecules are important for binding to and selecting cargos for transport.

You are working in a biotech company that has discovered a small-molecule drug called H5434. H5434 binds to LDL receptors when they are bound to cholesterol. H5434 binding does not alter the conformation of the LDL receptor's intracellular domain. Interestingly, in vitro experiments demonstrate that addition of H5434 increases the affinity of LDL for cholesterol and prevents cholesterol from dissociating from the LDL receptor even in acidic conditions. Which of the following is a reasonable prediction of what may happen when you add H5434 to cells?

Cytosolic cholesterol levels will decrease relative to normal cells.

Which of the following statements about disulfide bond formation is false?

Disulfide bonds form spontaneously within the ER because the lumen of the ER is oxidizing.

Which of the following choices reflects the appropriate order through which a protein destined for the plasma membrane travels?

ER → Golgi → plasma membrane

Which of the following statements about membrane-enclosed organelles is true?

In a typical cell, the area of the endoplasmic reticulum membrane far exceeds the area of plasma membrane.

What is the role of the nuclear localization sequence in a nuclear protein?

It is bound by cytoplasmic proteins that direct the nuclear protein to the nuclear pore.

Your friend works in a biotechnology company and has discovered a drug that blocks the ability of Ran to exchange GDP for GTP. What is the most likely effect of this drug on nuclear transport?

Nuclear transport receptors would be unable to release their cargo in the nucleus.

You are interested in Fuzzy, a soluble protein that functions within the ER lumen. Given that information, which of the following statement must be true?

Once the signal sequence from Fuzzy has been cleaved, the signal peptide will be ejected into the ER membrane and degraded.

Which of the following statements about the endoplasmic reticulum (ER) is false?

Proteins to be delivered to the ER lumen are synthesized on smooth ER.

15-19 Figure Q15-19 shows the organization of a protein that normally resides in the plasma membrane. The boxes labeled 1 and 2 represent membrane-spanning sequences and the arrow represents a site of action of signal peptidase. Given this diagram, which of the following statements must be true? Figure Q15-19

The C-terminus of this protein is cytoplasmic

Which of the following statements about secretion is true?

The membrane of a secretory vesicle will fuse with the plasma membrane when it discharges its contents to the cell's exterior.

15-33 Cells have oligosaccharides displayed on their cell surface that are important for cell-cell recognition. Your friend discovered a transmembrane glycoprotein, GP1, on a pathogenic yeast cell that is recognized by human immune cells. He decides to purify large amounts of GP1 by expressing it in bacteria. To his purified protein he then adds a branched 14-sugar oligosaccharide to the asparagine of the only Asn-X-Ser sequence found on GP1 (Figure Q15-33). Unfortunately, immune cells do not seem to recognize this synthesized glycoprotein. Which of the following statements is a likely explanation for this problem? Figure Q15.33

The oligosaccharide needs to be further modified before it is mature.

Which of the following protein families are not involved in directing transport vesicles to the target membrane?

adaptins

After isolating the rough endoplasmic reticulum from the rest of the cytoplasm, you purify the RNAs attached to it. Which of the following proteins do you expect the RNA from the rough endoplasmic reticulum to encode?

all of the above

Most proteins destined to enter the endoplasmic reticulum

begin to cross the membrane while still being synthesized.

Your friend has just joined a lab that studies vesicle budding from the Golgi and has been given a cell line that does not form mature vesicles. He wants to start designing some experiments but wasn't listening carefully when he was told about the molecular defect of this cell line. He's too embarrassed to ask and comes to you for help. He does recall that this cell line forms coated pits but vesicle budding and the removal of coat proteins don't happen. Which of the following proteins might be lacking in this cell line?

dynamin

Where are proteins in the chloroplast synthesized?

in both the cytosol and the chloroplast

In which cellular location would you expect to find ribosomes translating mRNAs that encode ribosomal proteins?

in the cytosol

Which of the following organelles are not part of the endomembrane system?

mitochondria

N-linked oligosaccharides on secreted glycoproteins are attached to

the asparagine in the sequence Asn-X-Ser/Thr.

An individual transport vesicle

will fuse with only one type of membrane