CELL BIO EXAM 2

In the primary research article the authors utilized a two step cell extraction method in Figure 1. What was the purpose and order of those steps?

Cell Shearing to break open and separate the cytoplasm from the membrane and them chemical homogenization to breakdown the remaining membranes

Which of the following statements is true?

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

Consider two genes that are next to each other on a chromosome, as arranged in the figure. Which of the following statements is true?

Gene A and gene B can be transcribed at different rates, producing different amounts of RNA within the same cell

If Na+ channels are opened in a cell that was previously at rest, how will the resting membrane potential be affected?

It becomes more positive

A poison added to an in vitro translation mixture containing mRNA molecules with the sequence 5'-AUGAAAAAAAAAAAAUAA-3' has the following effect: the only product made is a Met-Lys dipeptide that remains attached to the ribosome. What is the most likely way in which the poison acts to inhibit protein synthesis?

It inhibits movement of the small subunit relative to the large subunit.

Which of the following concentration gradients is considered a passive movement of a ions?

K+ moves out of the cell, Ca2+ moves into the cytosol, Na+ moves into the cell

Which of the following statements about the proteasome is false?

Misfolded proteins are delivered to the proteasome, where they are sequestered from the cytoplasm and can attempt to refold.

Unlike DNA, which typically forms a helical structure, different molecules of RNA can fold into a variety of three-dimensional shapes. This is largely because ___________________.

RNA is single-stranded

Which of the following statements about prokaryotic mRNA molecules is false? Hint: Keep in mind we really focused on discussions in lecture on eukaryotic cells. What aspect of central dogma is not applicable when we are talking about prokaryotic? What don't prokaryotes have?

Ribosomes must bind to the 5' cap before initiating translation.

The ribosome is important for catalyzing the formation of peptide bonds. Which of the following statements is true?

The catalytic site for peptide bond formation is formed primarily from an rRNA.

Which of the following statements about the genetic code is correct?

The genetic code is redundant.

A hungry yeast cell lands in a vat of grape juice and begins to feast on the sugars there, producing carbon dioxide and ethanol in the process: C6H12O6 + 2ADP + 2Pi + H+ 2CO2 + 2CH3CH2OH + 2ATP + 2H2O Unfortunately, the grape juice is contaminated with proteases that attack some of the transport proteins in the yeast cell membrane, and the yeast cell dies. Which of the following could account for the yeast cell's demise?

inability to import sugar into the cell

Cholesterol serves several essential functions in mammalian cells. Which of the following is not influenced by cholesterol?

membrane thickness

What do you predict would happen if you created a tRNA with an anticodon of 5'-CAA-3' that is charged with methionine, and added this modified tRNA to a cell-free translation system that has all the normal components required for translating RNAs?

methionine would be incorporated into proteins at some positions where leucine should be

The plasma membrane serves many functions, many of which depend on the presence of specialized membrane proteins. Which of the following roles of the plasma membrane could still occur if the bilayer were lacking these proteins?

selective permeability

Ribozymes catalyze which of the following reactions?

splicing Yes! Not only do the ribosomes work because RNAs act like enzymes but the spisosome is ALSO made up of RNAs that act like enzymes.

You have a segment of DNA that contains the following sequence: 5'-GGACTAGACAATAGGGACCTAGAGATTCCGAAA-3' 3'-CCTGATCTGTTATCCCTGGATCTCTAAGGCTTT-5' You know that the RNA transcribed from this segment contains the following sequence: 5'-GGACUAGACAAUAGGGACCUAGAGAUUCCGAAA-3' Which of the following choices best describes how transcription occurs?

the bottom strand is the template strand; RNA polymerase moves along this strand from 3' to 5'

Consider the apical location of a particular protein expressed in epithelial cells, illustrated in the figure. Which type of defect described below is the most likely to cause the redistribution of that protein around the entire cell, shown in the figure?

the deletion of a junctional protein

Cells use membranes to help maintain set ranges of ion concentrations inside and outside the cell. Which of the following ions is the most abundant outside a typical mammalian cell?

Na+

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 studying a disease that is caused by a virus, but when you purify the virus particles and analyze them you find they contain no trace of DNA. Which of the following molecules are likely to contain the genetic information of the virus?

RNA

Which of the following does not occur before a eukaryotic mRNA is exported from the nucleus?

The ribosome binds to the mRNA

Which of the following might decrease the transcription of only one specific gene in a bacterial cell?

a mutation that introduced extensive sequence changes into the DNA that precedes the gene's transcription start site

In the diagram it shows you two neurons that are in tandem in the brain (one right next to the other). When these cells need to have one turn on the next cell, cell 1 releases a neurotransmitter (ligand) or "propagate" the signal in the brain. What likely happens to "propagate" the electrical signal from cell one end terminal to cell 2 start receiver side?

a neurotransmitter passes between cells and activates the inward

The figure illustrates changes in membrane potential during the formation of an action potential. What membrane characteristic or measurement used to study action potentials is indicated by the arrow? Quiz 6 Q8.pdf

action potential

In the primary research article, why did the authors have to do the research in the first place?

because some scientists used different cell types and came up with different answers;because the difference in all of the data coming our about lipid rafts was confusing people; because some scientists used different detergents and came up with different responses

Signal sequences that direct proteins to the correct compartment are _________.

encoded in the amino acid sequence and sufficient for targeting a protein to its correct destination

In the primary article the authors separated their lipids using thin layer chromatography which separated them based on

polarity

The sigma subunit of bacterial RNA polymerase ___________________.

recognizes promoter sites in the DNA.

The concentration of a particular protein, X, in a normal human cell rises gradually from a low point, immediately after cell division, to a high point, just before cell division, and then drops sharply. The level of its mRNA in the cell remains fairly constant throughout this time. Protein X is required for cell growth and survival, but the drop in its level just before cell division is essential for division to proceed. You have isolated a line of human cells that grow in size in culture but cannot divide, and on analyzing these mutants, you find that levels of X mRNA in the mutant cells are normal. Which of the following mutations in the gene for X could explain these results?

the deletion of a sequence that encodes sites at which ubiquity can be attached to the protein