exam 1

Is the following statement true or false, and why? Within a developed multicellular organism, all cells possess the ability to divide and do so regularly.

You are part of an exobiology (the branch of science that deals with the possibility and potential nature of life on other planets) team studying potential life-forms on an asteroid. Your team is testing the hypothesis that alien life-forms would also be composed of cells, just like terrestrial (Earth-based) life-forms. You have identified several structures that you think might be cells of alien life-forms. Which of the following criteria would be MOST useful in determining whether or not these structures could be cells?

In 1970, Frye and Edidin published research describing the mobility of plasma membrane proteins. They fused mouse and human cells together, creating a hybrid cell, and then examined the localization of mouse and human proteins over time. Initially mouse and human proteins were each restricted to one-half of the heterokaryon, but over time the mouse and human proteins mixed, with each being present over the entire cell surface. What technique did Frye and Edidin likely use to examine the mouse and human proteins?

Which statement represents the cell theory?

You are a biologist interested in studying how eukaryotic cells obtained their unique features during their evolution from a prokaryotic ancestor. Which cellular features, unique to eukaryotes, might you focus on?

Antibiotics tend to target features that are unique to bacterial cells and absent from eukaryotic cells such as our own. Which of the following would present a safe target for a new antibiotic?

Which is not evidence for the endosymbiotic origins of mitochondria and chloroplasts?

You are studying a recently discovered protozoan and have found what appears be a new organelle of unknown function. You hypothesize that it may have resulted from a new endosymbiotic event. Which of the following properties of the organelle would support this hypothesis? Choose all that apply—there may be more than one correct answer.

The accumulation of mutations in DNA is the basis for evolution and organismal divergence. The amount of divergence can be measured by comparing the sequences of homologous genes. Which of the following statements is most likely to be true?

Scientists were studying yeast cells in which a mutation inactivated a gene required for cell division. Without this gene—and the protein it encoded—these mutant yeast cells were unable to divide normally. But the scientists discovered that introducing a related protein from human cells could “rescue” these mutant yeast cells, allowing the cells to resume normal division. Based on this finding, what is the most likely conclusion you could make?

Although the influenza virus and the SARS-CoV-2 virus are two completely unrelated viruses, both have RNA genomes, and both infect humans by binding to cells of the respiratory tract. Based on the success of the SARS-CoV-2 vaccine, you have decided to try to develop an influenza vaccine that takes the same strategy. Which of the following describes the approach you should use to follow the SARS-CoV-2 vaccine approach?

We have learned a great deal about human cell biology from human cell lines grown in tissue culture. Both primary cell lines (cells isolated from normal differentiated tissue that maintain the properties of the original tissue) and some cell lines derived from embryonic (i.e., nondifferentiated) cells can be induced in culture to show the properties of mature differentiated cells. Given this information, which of the following statements describes how we should think about cultured cells as a tool to study human biology?

Why do cell biologists study yeast?

Radioactive isotopes (radioisotopes) of elements are commonly used in biological experiments as tracers to follow and detect molecules of interest. For example, photosynthetic intermediates produced during carbon dioxide conversion to sugars were detected by exposing algae to carbon dioxide containing a radioactive form of carbon. This radioactive carbon could be rapidly detected in molecules produced by the algae during carbon fixation and sugar production. Why can radioisotopes substitute for non-radioactive isotopes of elements in experiments?

Approximately how much does a mole of carbon atoms (each having an atomic weight of 12) weigh?

Which type of covalent bond allows for rotation about the bond axis?

The melting point of an ionic solid is the temperature at which the crystal separates into its constituent ions. For sodium chloride, the melting point in air is 801°C. However, when sodium chloride is added to water at 37°C (human body temperature), the sodium and chloride ions separate readily. How can we explain this apparent paradox?

You have developed a promising anti-cancer agent, but it has poor solubility in water. Which of the following changes should improve water solubility?

On the basis of weight, which is most abundant in a living bacterial cell?

The ultracentrifuge is an important piece of laboratory equipment frequently used by cell biologists. What are some applications for the ultracentrifuge?

What evidence may have led you to conclude that the molecule is a macromolecule?

What type(s) of bonds link together the components of a ribosome, as shown in the figure?

Which of the following would most likely interact by forming an ionic bond?

The hydrophobic “force” results from the fact that it is energetically unfavorable for hydrophobic molecules to disrupt the hydrogen bonding network of water. This drives hydrophobic amino acid side chains to interact with each other during protein folding, typically in the interior of the protein. What would you expect to happen if a protein folded in a hydrophobic environment such as the lipid bilayer of a cellular membrane?