Test Prep for AP® Courses
Urey and Miller constructed an experiment to illustrate the early atmosphere of 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
- Hydrogen, methane, water, and ammonia combined to create amino acids.
- Hydrogen, methane, and oxygen combined to create macromolecules.
- Nitrogenous bases combined to form monomers, then RNA.
- Periodic elements combined to create molecules, then DNA.
How does Urey and Miller'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 the large complexes, such as water and methane.
- The inorganic molecules assembled to form the amino acids and nucleic acids.
- The inorganic molecules assembled to form the large complexes, such as water and methane.
- 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.
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 one 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.
- The primitive atmosphere cannot be created due to the oxidizing atmosphere and lack of hydrogen.
- The primitive atmosphere can be created as the atmosphere is reducing and the Earth has sufficient hydrogen to reproduce the conditions.
- The primitive atmosphere cannot be created due to the presence of abundant water and hydrogen in the atmosphere.
- The primitive atmosphere can be created as the atmosphere is oxidizing and has less of hydrogen.
What is structurally different between starch and cellulose that gives them different physical properties?
- Cellulose is formed by β- 1-4 glycosidic linkages and crosslinks, making it rigid, while starch has α- 1-4 and α- 1-6 glycosidic linkages without the tight crosslinks of cellulose.
- Cellulose has rigid α- 1-4 glycosidic linkages, while starch has less rigid β- 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.
Complex polymers are built from combinations of smaller monomers. What type of reaction is illustrated in the figure, and what is the product of the reaction?
- a synthesis reaction producing glucose
- a hydrolysis reaction producing fructose
- a condensation reaction producing lactose
- a dehydration reaction producing water
- 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.
- Unsaturated fats and trans fats have some double bonded carbon atoms, while saturated fats do not.
- Unsaturated and trans fats are the same; the fatty acids are just found on opposite sides of a trans fat.
- Chitin is a nitrogen-containing polysaccharide, with repeating units of N-acetyl--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 plus additional glucose monomers.
- Chitin contains phosphate groups that give it a stiffness not found in other polysaccharides.
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?
- Nonpolar and charged amino acids will be present on the surface and polar in the interior of the membrane, whereas nonpolar will be found in the membrane embedded proteins.
- Nonpolar and uncharged proteins will be found on the surface with nonpolar in the interior, while only nonpolar will be found in the embedded proteins.
- Polar and charged amino acids will be found on the surface, whereas nonpolar in the interior.
- Polar and charged amino acids will be found on the surface of a membrane protein, whereas nonpolar in the interior. The membrane protein will be polar and hydrophobic.
You have been identifying the sequence of a segment of a protein. The sequence to date is: leucine-methioninetyrosine-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 nonpolar, 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.
Predict what happens if even one amino acid is substituted for another in a polypeptide and provide a specific 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.
- replication errors
- The DNA and protein of the virus were tagged with different isotopes and exposed to the host cell, whereas 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.
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: ATC/GTT/GAA/CTG/TAG/GAT/AAA
- A substitution of T for A, resulting in a coding change for the third codon.
- An addition of C for G, lengthening the strand and changing every codon past the addition.
- A deletion of an 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.
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. Explain the difference between the effects of the changes in the two types of nucleic acids.
- DNA is the genetic material that is passed from parent cells to daughter cells and to future generations.
- DNA would not affect the individuals as the proteins made are finally altered and modified. RNA would cause harm to the person as the RNA is encoded by the DNA and is not altered.
- DNA is the genetic material and is transferred from one generation to another, making use of repair mechanisms for every mutation. The RNA does not use a repair mechanism.
- DNA, when mutated, makes use of the repair mechanisms and can be repaired, whereas RNA is not repaired and is transferred in generations.