Biology Exam 2

Five dialysis bags, constructed from a semipermeable membrane that is impermeable to sucrose but permeable to water, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed (see the figure above) Which line in the graph represents the bag with the lowest initial concentration of sucrose?

E

At puberty, an adolescent female body changes in both structure and function of several organ systems, primarily under the influence of changing concentrations of estrogens and other steroid hormones. How can one hormone, such as estrogen, mediate so many effects?

Estrogen binds to specific receptors inside many kinds of cells, each of which have different responses to its binding

H1N1 flu is a highly contagious viral infection caused by the influenza A (H1N1) virus. The symptoms of H1N1 are listed in the box. An antiviral agent such as Tamiflu® administered within 48 hours of the appearance of symptoms can reduce the severity of the illness. Why is it important to administer an antiviral agent to an infected person within 48 hours of the appearance of symptoms?

The H1N1 virus replicates quickly.

Some students used vinegar to dissolve away the shells of three eggs and used these eggs as models of human red blood cells. The students observed the changes in the eggs when they were placed in different solutions.Which statement best describes the role of the cell membrane in this model?

The cell membrane allows water to enter and leave the cell.

A researcher lyses (breaks open) a cell that contains nucleic acid molecules and capsomeres of tobacco mosaic virus (TMV). The cell contents are left in a covered test tube overnight. The next day this mixture is sprayed on tobacco plants. Which of the following would be expected to occur?

The plants would develop the typical symptoms of TMV infection.

The diagram above shows how a paramecium maintains homeostasis. A paramecium normally lives in a hypotonic environment in which water continually diffuses into the cell. To maintain homeostasis, the paramecium must pump out large amounts of water using its contractile vacuole. If the paramecium is then placed in a hypertonic environment, which of the following will occur?

Water will diffuse out of the paramecium.

The cell membranes of Antarctic ice fish might have which of the following adaptations?

a high percentage of polyunsaturated fatty acids

In order to be able to remain latent (dormant) in an infected live cell, herpes simplex virus (HSV) must be able to shut down what process?

apoptosis (cell death) of a virally infected cell

Electron microscopes are very powerful and can see smaller images than a light microscope. What is one advantage, however, of light microscopy over electron microscopy?

light microscopy allows one to view dynamic processes in living cells.

A bacterium engulfed by a white blood cell through phagocytosis will be digested by enzymes contained in

lysosomes.

The presence of cholesterol in the plasma membranes of some animals (select all that apply)

enables the membrane to stay less fluid when cell temperature increases. enables the membrane to stay fluid more easily when cell temperature drops.

Which of the following can be effective in preventing the onset of viral infection in humans?

getting vaccinated

Cyanide is a deadly poison. When cyanide enters the body it binds to at least one molecule involved in producing ATP. If you were to examine the cells of a person who had been exposed to cyanide, most of the cyanide would be found within the

mitochondria.

The difference between pinocytosis and receptor-mediated endocytosis is that

pinocytosis is nonselective in the molecules it brings into the cell, whereas receptor-mediated endocytosis offers more selectivity.

Vinblastine, a drug that inhibits microtubule polymerization, is used to treat some forms of cancer. Cancer cells given Vinblastine would be unable to

separate chromosomes during cell division

A primary objective of cell fractionation is to

separate the major organelles so that their particular functions can be determined.

What kinds of molecules pass through a cell membrane most easily?

small and hydrophobic

As a biologist working on your PhD thesis, your research focuses on the endocrine system; specifically the production of steroids in the body such as testosterone, estrogen, and cholesterol. What organelle is of particular importance to your research as it is primarily involved in the synthesis of these steroids?

smooth endoplasmic reticulum

Tay-Sachs disease is a human genetic abnormality that results in cells accumulating and becoming clogged with very large, complex, undigested lipids. Which cellular organelle must be involved in this condition?

the lysosome

Emerging viruses arise by (select all that apply)

the spread of existing viruses more widely within their host species. the spread of existing viruses to new host species. mutation of existing viruses

Five dialysis bags, constructed from a semipermeable membrane that is impermeable to sucrose but permeable to water, were filled with various concentrations of sucrose and then placed in separate beakers containing an initial concentration of 0.6 M sucrose solution. At 10-minute intervals, the bags were massed (weighed) and the percent change in mass of each bag was graphed (see the figure above) Which line in the graph represents the bag that contained a solution isotonic to the 0.6 M solution at the beginning of the experiment?

C

The HIV virus attacks only a certain type of white blood cells, and not other cell types. Why?

HIV receptors are not found on the other cell types.

The diagram shows cellular activity across a cell membrane. Which two processes does this diagram most directly model?

Homeostasis and transport of molecules

ou isolate an infectious substance that is capable of causing disease in plants, but you do not know whether the infectious agent is a bacterium or a virus. You have four methods at your disposal that you can use to analyze the substance in order to determine the nature of the infectious agent. Which treatment would allow you to distinguish between these two possibilities? I. treating the substance with nucleases that destroy all nucleic acids and then determining whether it is still infectious II. filtering the substance to remove all elements smaller than what can be easily seen under a light microscope III. culturing the substance by itself on nutritive medium, away from any plant cells IV. treating the sample with proteases that digest all proteins and then determining whether it is still infectious

III

The 1918 influenza epidemic killed between 50 million and 100 million people worldwide. This epidemic happened near the end of World War I. More people died from the influenza epidemic than were killed in the war. Which of the following explains why this virus was so deadly worldwide? (Select all that apply)

Infected soldiers returning from the war spread the virus when they coughed. Medical personnel often became ill as a result of exposure to airborne virus particles. Food was scarce because of the war, so people were undernourished, and their immune systems were weakened.

The cellular process known as the sodium-potassium pump was discovered in the 1950s by Jens Christian Skou, a Danish scientist. This process is a form of active transport that moves three sodium ions to the outside of a cell for every two potassium ions that it moves into the cell. Which of these best explains why energy is needed for active transport?

Ions are moved against the concentration gradient.

Antibiotics are used to treat bacterial infections. The overuse of antibiotics, however, has caused bacterial resistance to these antibiotics to increase. Now there are so called "super bugs", which are bacterial species where few, if any, antibiotic treatments will work. As a research scientist, you are trying to solve this problem by engineering a virus to combat a bacterial infection, specifically the bacterium Escherichia coli. What type of virus must you use in your research?

T4 phage virus

Models of the human immunodeficiency virus (HIV) and an animal cell are shown below. What is the difference in the function of the glycoprotein structures of an HIV virion and the cilia of an animal cell?

The glycoprotein structures are used for attachment, and the cilia are used to move fluids surrounding the cell.

Match the organelle to the phrase or sentence that describes it best. Each choice may be used once, more than once, or not at all.

These organelles are not found in red blood cells but are present in large numbers in muscle cells - mitochondria An organelle with cis and trans face, which acts as the packaging and secreting center of the cell - Golgi Apparatus Large membrane-bound structures that contain hydrolytic enzymes and that are found predominantly in animal cells - Lysosomes An organelle that is characterized by extensive, folded membranes and is abundant in cells that detoxify poisons, such as liver cells - Smooth ER

The nuclear lamina is an array of filaments on the inner side of the nuclear membrane. If a method were found that could cause the lamina to fall into disarray, what would you expect to be the most likely immediate consequence?

a change in the shape of the nucleus

In a plant cell, DNA may be found

in the nucleus, mitochondria, and chloroplasts.

The herpesviruses are very important enveloped DNA viruses that cause disease in all vertebrate species and in some invertebrates such as oysters. Some of the human ones are herpes simplex virus (HSV) types I and II, causing facial and genital lesions, and the varicella zoster virus (VSV), causing chicken pox and shingles. Each of these three actively infects nervous tissue. Primary infections are fairly mild, but the virus is not then cleared from the host; rather, viral genomes are maintained in cells in a latent phase. The virus can then reactivate, replicate again, and be infectious to others. If scientists are trying to use what they know about HSV to devise a means of protecting other people from being infected, which of the following would have the best chance of lowering the number of new cases of infection?

interference with new viral replication in preexisting cases

A cell has the following molecules and structures: enzymes, DNA, ribosomes, plasma membrane, and mitochondria. It could be a cell from

nearly any eukaryotic organism.

Which of the following characteristics, structures, or processes is common to both bacteria and viruses? (select all that apply)

nucleic acids proteins

Zellweger syndrome, also called cerebrohepatorenal syndrome, is a rare congenital disorder characterized by the inability to break down very long chain fatty acids (VLCFA) and branched chain fatty acids (BCFA). The organelle that is defective in these individuals is also responsible for the removal of hydrogen atoms in alcohol (thus metabolizing it). Which organelle is defective in individuals with Zellweger syndrome?

peroxisome

Which of the following types of molecules are the major structural components of the cell membrane?

phospholipids and proteins

n humans, viral DNA that is integrated into the host genome is called a

provirus

Which of the following do prokaryotic and eukaryotic cells both contain (select all that apply)

ribosomes, cell walls , DNA , plasma membrane

Insulin is a protein synthesized in the cytoplasm of pancreas cells and then transported to the plasma membrane where it enters the blood stream. Which of the following summarizes the pathway for insulin through a pancreatic cell?

rough ER → Golgi body → vesicle → plasma membrane

Pancreatic cells, like the one shown below, produce a lot of protein digesting enzymes. If you were able to examine a pancreatic cell under an electron microscope, what type of organelle would you expect to see a lot of?

rough endoplasmic reticulum

Celery stalks that are immersed in fresh water for several hours become stiff and hard. Similar stalks left in a 0.15 M salt solution become limp and soft. From this we can deduce that

the fresh water is hypotonic and the salt solution is hypertonic to the cells of the celery stalks.