58.
Urey and Miller constructed an experiment to illustrate the early atmosphere of the Earth and possible development of organic molecules in the absence of living cells. Which assumption did Urey and Miller make regarding conditions on Earth?
-
electric sparks occurred to catalyze the reaction
-
the composition of the gases in the atmosphere
-
there was sufficient oxygen for creating life
-
it produced water-soluble organic molecules
59.
Urey and Miller proposed that a series of reactions occurred, which ultimately resulted in amino acid formation. Which of the following is true based upon their theory?
-
Hydrogen and nitrogen combined to create amino acids.
-
Hydrogen and oxygen combined to create macromolecules.
-
Nitrogenous bases combined to form monomers then RNA.
-
Periodic elements combined to create molecules then DNA.
60.
How does Stanley Miller and Harold Urey’s model support the claim that simple precursors present on early Earth could have assembled into complex molecules necessary for life?
-
The simple molecules assembled to form amino acids and nucleic acids.
-
The organic molecules assembled to form large complexes such as starch and RNA.
-
The inorganic molecules assembled to form the amino acids and nucleic acids.
-
The inorganic molecules assembled to form large complexes such as starch and RNA.
61.
Which statement most accurately describes the importance of the condensation stage during Urey and Miller’s experiment?
-
Condensed water enabled the formation of monomers.
-
Condensation and evaporation simulated lightning storms.
-
Condensation and evaporation simulated the water cycle.
-
Condensed water enabled the formation of polymers.
62.
According to the findings of the Urey and Miller experiment, the primitive atmosphere consisted of water in the form of steam, methane, ammonia, and hydrogen gases. If there was so much hydrogen gas in the early atmosphere, why is there so little now?
-
Hydrogen gas is so light with a molecular weight of 1 that the excess diffused into space over time and is now absent from the atmosphere.
-
Hydrogen combined with ammonia to make ammonium.
-
It was all used up in the production of organic molecules.
-
The excess hydrogen gas was dissolved in the early oceans.
63.
How is the Earth's atmosphere today different from the primitive atmosphere Miller and Urey modeled in the lab?
-
The modern atmosphere is more oxidizing and lacks hydrogen.
-
The modern atmosphere is less oxidizing and lacks hydrogen.
-
The primitive atmosphere is more oxidizing and lacks hydrogen.
-
The primitive atmosphere is less oxidizing and lacks hydrogen.
64.
What is structurally different between starch and cellulose that gives them different physical properties?
-
Cellulose is formed by \unicode[Arial]{x3B2}-1,4 glycosidic linkages and crosslinks, making it rigid. Starch has \unicode[Arial]{x3B1}-1.4 and \unicode[Arial]{x3B1}-1.6 glycosidic linkages without the tight crosslinks of cellulose.
-
Cellulose has rigid \unicode[Arial]{x3B1}-1,4 glycosidic linkages while starch has less rigid \unicode[Arial]{x3B2}-1,4 glycosidic linkages
-
Cellulose has amylose and amylopectin, making it more rigid than starch.
-
Starch has amylose and amylopectin that make it more rigid than cellulose.
65.
Complex polymers are built from combinations of smaller monomers. What type of reaction is shown, and what is a product of the following reaction? Assume water is also produced.
-
a synthesis reaction producing glucose and water
-
a hydrolysis reaction producing fructose and water
-
a condensation reaction producing lactose and water
-
a dehydration reaction producing sucrose and water
66.
The fatty acids of triglycerides are classified as saturated, unsaturated, or trans fats. What is it about the structure of these compounds that distinguishes them from each other?
-
Saturated fats and trans fats contain the greatest possible number of hydrogen atoms, while unsaturated fats do not.
-
Saturated and unsaturated fats have stable configurations, while trans fats are transient.
-
Trans fats are a type of unsaturated fat where the hydrogens around the double bond are not in the same plane.
-
Trans fats are a type of saturated fat that is produced artificially by hydrogenation.
67.
Carbohydrates serve various functions in different animals. Arthropods like insects, crustaceans, and others, have an outer layer, called the exoskeleton, which protects their internal body parts. This exoskeleton is made mostly of chitin. Chitin is also a major component of the cell walls of fungi, the kingdom that includes molds and mushrooms. Chitin is a polysaccharide. What is the major difference between chitin and other types of polysaccharides?
-
Chitin is a nitrogen-containing polysaccharide, with repeating units of N-acetyl-\unicode[Arial]{x3B2}-D-glucosamine, a modified sugar.
-
Chitin is similar to amylase, but with sulfur linkages between the monomers.
-
Chitin is similar to inulin, a polysaccharide with fructose, but with additional glucose monomers.
-
Chitin contains phosphate groups that give it a stiffness not found in other polysaccharides.
68.
What categories of amino acids would you expect to find on the surface of a soluble protein and which would you expect to find in the interior? Which of these are some examples for each part of the answer?
-
Non-polar and charged amino acids will be present on the surface and polar in the interior of the membrane whereas non-polar will be found in the membrane embedded proteins.
-
Non-polar and uncharged proteins will be found on the surface with non-polar in the interior, while only non-polar will be found in the embedded proteins.
-
Polar and charged amino acids will be found on the surface whereas non-polar in the interior.
-
Polar and charged amino acids will be found on the surface of a membrane protein whereas non-polar in the interior. The membrane protein will be polar and hydrophobic.
69.
You have been identifying the sequence of a segment of a protein. The sequence to date is: leucine-methionine-tyrosine-alanine-glutamine-lysine-glutamate. You insert arginine between the leucine and methionine. What effect would this have on the segment?
-
Arginine is a negatively charged amino acid and could attach to the glutamate at the end of the segment
-
Inserting arginine places a positively charged amino acid in a portion that is non-polar, creating the possibility of a hydrogen bond in this area.
-
There would be no effect other than an additional amino acid.
-
The arginine could attach to the lysine and bend the protein chain at this point.
70.
What would happen if even one amino acid is substituted for another in a polypeptide? What would be an example?
-
The change will definitely not be sufficient to have any effect on the function and structure of the protein.
-
The amino acid may not show any significant effect the protein structure and function or it may have a significant effect, as in the case of hemoglobin in individuals with sickle cell trait.
-
These changes would increase the possibility of having extra bends and loops in the proteins as in Leber congenital disease.
-
These changes would modify the structures of proteins making them nonfunctional.
71.
HIV is an RNA virus that affects CD4 cells, also known as T cells, in the human body. Which mechanism is most likely responsible for the fast rate at which HIV can spread?
-
recombination
-
mutation
-
reassortment
-
formation errors
72.
For many years, scientist believed that proteins were the source of heritable information. There are many thousands of different proteins in a cell, and they mediate the cell’s metabolism, producing the traits and characteristics of a species. Researchers working with DNA viruses proved that it is DNA that stores and passes on genes. They worked with viruses with an outer coat of protein and a DNA strand inside. How did they prove that it was DNA, not protein, which is the primary source of heritable information?
-
The DNA and protein of the virus were tagged with different isotopes and exposed to host cell where only the DNA was transferred to the host.
-
The DNA was tagged with an isotope, which was retained in the virus, proving it to be the genetic material.
-
The viral protein was tagged with an isotope, and the host cell was infected by it. This protein was transferred to the host.
-
The viral DNA, when sequenced, was found to be present in the host cell proving it to be the hereditary material instead of protein.
73.
The genetic code is based on each amino acid being coded for by a distinctive series of three nucleic acid bases called a codon. The following is a short segment of DNA using the slash symbol ( / ) to separate the codons for easy viewing:
\text{ATC/GTT/GAA/CTG/TAG/GAT/AAA}
A change has occurred in the segment resulting in the following:
\text{ATC/GTT/GTA/CTG/TAG/GAT/AAA}
What kind of change has occurred?
-
A substitution of \text{T} for \text{A}, changing the coding for the third codon
-
An addition of \text{C} for \text{G}, lengthening the strand and changing every codon past the addition
-
A deletion of an \text{A}, resulting in a shortening and changing every codon past the deletion
-
No change has occurred; the same one base was replaced with the same one
74.
A change in DNA on a chromosome affects all proteins made from that gene for the life of the cell. A change in the RNA involved in protein production is short lived. What is the difference between the effects of the changes in the two types of nucleic acids?
-
DNA is passed on to the daughter cell, permanently altering the genetic material.
-
Although short lived, a change in RNA can be lethal as it sets off a biological feedback loop.
-
A change in DNA is benign as DNA has repair mechanisms that RNA lacks.
-
Any change in DNA will immediately cause the cell to undergo apoptosis.