Question 1

In modern microbiology laboratories, scientists use sterile pipettes to transfer liquid cultures of microorganisms from one flask to another.The pipettes are sterilized by heating at very high temperatures, followed by cooling before use.Using sterile technique allows microbiologists to be confident that their cultures contain only the microorganisms that they want to work with and no others.This is possible because using sterile technique is an application of Pasteur's experiment in which he proved that living organisms do not arise by _______ from nonliving matter.

Accepted Answer

The answer of In modern microbiology laboratories, scientists use sterile...

Question 2

When J.William Schopf observed chains and clumps that resembled modern cyanobacteria in Australian sedimentary rocks, he concluded that these were remains of living organisms because

Accepted Answer

A)  the structures were near-perfect spheres, a form rarely found in nature. 
B)  the structures had an equal ratio of l- and d-amino acid isomers. 
C)  the structures had internal substructures that are characteristic of living systems. 
D)  the structures were in sediments deposited far from water. 
E)  the sediments indicated that oxygen had been consumed.

Question 3

Miller and Urey found that several different amino acids were formed during their first experiment using heated gases treated with electric sparks.The gas _______ was likely responsible for providing the source of nitrogen atoms that ended up in these amino acids, and water vapor was the likely source of oxygen atoms in these same molecules.

Accepted Answer

The answer of Miller and Urey found that several different...

Question 4

Scientists have generated protocells under lab conditions using different combinations of fatty acids.They have found that branched but not straight-chain fatty acids allow nucleotides to pass into protocells from the surrounding environment.Why is this an important finding in the study of the evolution of life?

Accepted Answer

A)  It signifies that both branched and straight-chain fatty acids must have existed on primordial Earth. 
B)  It shows that primitive cells developed with different membrane compositions. 
C)  It indicates that even very simple cell structures could take up molecules from the environment to fuel internal reactions. 
D)  It demonstrates that RNA molecules were likely the first biomolecules to catalyze chemical reactions. 
E)  It provides support for the idea that long-chain molecules could act as templates for transmitting biological information.

Question 5

The figure shows a cut away view of a structure used in experiments investigating the evolution of life on Earth.  These experiments were pivotal in finding evidence for the emergence of cells as the fundamental unit of life, because they focused on how a primitive _______ was able to form, creating a barrier between internal and external environments.

Accepted Answer

The answer of The figure shows a cut away view...

Question 6

Why did the Miller‒Urey hot chemistry experiment exclude oxygen in its investigation of the chemical origin of life on Earth?

Accepted Answer

A)  Oxygen is not necessary for life. 
B)  The scientists assumed the reactions would produce oxygen from water vapor. 
C)  The scientists assumed that photosynthetic organisms would develop in the apparatus. 
D)  There is no evidence that oxygen existed in Earth's earliest environments. 
E)  The scientists wanted to avoid contamination of the apparatus by oxygen-consuming bacteria.

Question 7

In a DNA double helix, a given purine can be paired with

Accepted Answer

A)  only one type of purine. 
B)  only one type of pyrimidine. 
C)  either one of two types of purine. 
D)  either one of two types of pyrimidine. 
E)  either a purine or a pyrimidine.

Question 8

In experiments measuring the rates at which different monosaccharides diffuse across phospholipid membranes, it was found that the rates followed this pattern (from slowest to fastest): glucose < mannose < arabinose < xylose < ribose.What aspect of the current theories about the origin of life do these results support?

Accepted Answer

A)  It is thought that simple sugars were synthesized from simple molecule precursors in the primordial soup of early Earth. 
B)  It is thought that nucleotides arose as the result of bond formation between sugar molecules, phosphate ions, and organic bases. 
C)  It is thought that RNA was the first molecule to serve a catalytic function in the evolution of cells. 
D)  It is thought that proteins became the primary catalytic molecules in modern cells because their ability to carry out catalytic functions is superior to that of RNA. 
E)  It is thought that the evolution of living cells depended on the chemical evolution of certain biomolecules that serve as building blocks for biomacromolecules.

Question 9

Single-stranded RNA can fold back on itself, creating three-dimensional structures such as tRNA.The folds are stabilized by _______ bonds.

Accepted Answer

A)  hydrogen 
B)  ionic 
C)  phosphodiester 
D)  peptide 
E)  glycosidic

Question 10

Retroviruses, such as HIV, have an enzyme that allows them to catalyze DNA synthesis from an RNA template.This evidence supports the hypothesis that

Accepted Answer

A)  RNA itself cannot be a catalyst. 
B)  early life consisted of an "RNA world." 
C)  RNA probably came from an extraterrestrial source. 
D)  chemical evolution led to polymerization. 
E)  DNA polymers form from RNA monomers.

Question 11

In DNA, bonding of A with T and bonding of C with G are examples of

Accepted Answer

A)  complementary base pairing. 
B)  a dehydration reaction. 
C)  a reduction reaction. 
D)  a hydrophobic interaction. 
E)  a purine-purine interaction.

Question 12

In the first Miller-Urey experiment, an electrical spark was passed through an experimental "atmosphere" consisting of hydrogen gas, ammonia, methane gas, and water vapor.A limitation of this experiment was that it

Accepted Answer

A)  assumed that the spark could catalyze reactions. 
B)  did not include certain gasses later considered to be part of the early Earth atmosphere. 
C)  did not freeze the constituents. 
D)  did not contain atmospheric oxygen. 
E)  did not correctly simulate the effects of hydrothermal vents.

Question 13

Refer to the figure below illustrating Louis Pasteur's experiment on spontaneous generation.  The experiment supports which hypothesis?

Accepted Answer

A)  Amino acids are the building blocks of life. 
B)  Some forms of life can arise by spontaneous generation. 
C)  Oxygen is needed for life. 
D)  Life comes from decaying matter. 
E)  Life comes from preexisting life.

Question 14

Changes to the original Miller‒Urey hot chemistry experiment included adding other gases like carbon dioxide (CO2), nitrogen (N2), hydrogen sulfide (H2S), and sulfur dioxide (SO2) in the test apparatus, which resulted in the production of more small molecules of life than the original experiment had produced.Which products were shown to be significant for the synthesis of proteins?

Accepted Answer

A)  All five bases that are present in nucleic acids (i.e., A, T, C, G, and U) 
B)  All of the 20 standard amino acids 
C)  Many 3- to 6-carbon sugars 
D)  Certain fatty acids 
E)  Small carboxylic acids

Question 15

Many enzymes in organisms living today have metal cofactors such as iron or zinc that participate directly in the reactions they catalyze.How might this property reflect the evolution of catalysts in living organisms, reaching all the way back to prebiotic times before living cells arose?

Accepted Answer

The answer of Many enzymes in organisms living today have...

Question 16

Why was the evolution of a self-contained cell essential for life as we know it?

Accepted Answer

The answer of Why was the evolution of a self-contained...

Question 17

When fatty acid molecules are in water, they can self-organize into a bilayer (double layer) that surrounds an inner core of water.Where "middle" refers to the middle of the bilayer between the outer and inner layers of fatty acids, which of the following statements is correct?

Accepted Answer

A)  The polar heads of the outer layer face outward; the polar heads of the inner layer face toward the middle. 
B)  The polar heads of the outer layer face outward; the polar heads of the inner layer face toward the inner water core. 
C)  The polar tails of the outer layer face outward; the polar tails of the inner layer face toward the middle. 
D)  The polar heads of the outer layer face the middle; the polar heads of the inner layer face toward the middle. 
E)  The polar tails of the outer layer face toward the middle; the polar tails of the inner layer face toward the inner water core.

Question 18

One way that modern enzymes increase reaction rates is to increase the chance for collision between molecules by binding them in close proximity to each other.Enzymes also increase rates by orienting reacting molecules in three-dimensional space to facilitate attack of one substrate by another.The figure below shows an organic molecule adsorbing onto a clay mineral surface.  How do the properties of enzymes mentioned above relate to the way that clay minerals are hypothesized to have been instrumental in the rise of life?

Accepted Answer

The answer of One way that modern enzymes increase reaction...

Question 19

A woman buys a fresh loaf of bread wrapped in a plastic bag.She removes several slices of the bread and closes the bag tightly before storing the bread in her pantry.When she takes the loaf out several days later, she is dismayed to see mold growing on the bread.She recognizes that mold spores must have landed on the bread before she closed the bag for storage in her pantry, because she knows that living organisms do not arise through _______.

Accepted Answer

The answer of A woman buys a fresh loaf of...

Question 20

The original Miller-Urey experiment did not include several gasses later shown to have occurred on the primordial Earth, including CO2, N2, and SO2. When scientists ran a new experiment incorporating these gasses, which of the following was not produced?

Accepted Answer

A)  All five bases that are present in DNA and RNA 
B)  Phospholipids 
C)  Nicotinamide (part of NA
D)  
D)  Many three- to six-carbon sugars 
E)  Certain fatty acids

Exam 4: Nucleic Acids and the Origin of Life