Question 1

According to Fox's laboratory experiments,the protocell could have been composed

Accepted Answer

After macromolecules formed, something similar to a modern plasma membrane was needed to separate them from the environment. Thus, before the first true cell arose, there would likely have been a protocell, a structure that had a lipid-protein membrane and carried on energy metabolism. Fox has shown that if lipids are made available to microspheres the two tend to become associated and produce a lipid-protein membrane.Bloom's

Question 2

In a liquid environment,____ molecules will automatically form droplets called liposomes.

Accepted Answer

A liposome is a microscopic sac formed by fatty acids, in this case phospholipids. In an aqueous environment they will arrange themselves into a spherical shape to keep the hydrophobic portion of the molecules out of the liquid.Bloom's

Question 3

The first cell is believed to have carried on anaerobic respiration.This means that it would have

Accepted Answer

Anaerobic respiration is a metabolic pathway that extracts energy from preformed molecules without the presence of oxygen. It combines glycolysis and a step that regenerates the molecules necessary for glycolysis. The entire process is called fermentation.Bloom's

Question 4

Biological evolution (the evolution of living cells)differs from chemical evolution (the evolution of the molecules that make living cells)in that biological evolution would have been possible only after the development of

Accepted Answer

Since the definition of biological evolution requires that living cells exist to be acted upon then it can only occur after true cells exist.Bloom's

Question 5

A complex protein-rich cell shelters and supports the DNA genetic code,and the code is the blueprint for the cell proteins; thus is set the "chicken-or-the-egg" dilemma of which came first.This is probably solved by the discovery that

Accepted Answer

The first true cell would have contained RNA genes that could have replicated because of the presence of proteins. This eliminates the baffling chicken-and-egg paradox: which came first, proteins or RNA? It does mean, however, that two unlikely events would have had to happen at the same time.Bloom's

Question 6

Which theory would suggest that both polypeptides and RNA arose at the same time.

Accepted Answer

A combination of these RNA-first and the protein-first hypotheses was put forth by Alexander Cairns-Smith. He thinks that clay was especially helpful in causing the polymerization of both polypeptides and RNA at the same time. Clay attracts small organic molecules and contains iron and zinc, which may have served as inorganic catalysts for polypeptide formation. In addition, clay tends to collect energy from radioactive decay and then discharges it when the temperature or humidity changes, possibly providing a source of energy for polymerization. Cairns-Smith suggests that RNA nucleotides and amino acids became associated in such a way that polypeptides were ordered by, and helped synthesize, RNA.Bloom's

Question 7

The synthesis of DNA or RNA from the organic soup would have been guided by the actions of enzymes in the

Accepted Answer

The protein-first hypothesis suggests that proteins, or at least polypeptides, were the first of the three molecules to arise. Only after the protocell developed sophisticated enzymes did it have the ability to synthesize DNA and RNA from small molecules provided by the ocean. Researchers point out that because nucleic acids are very complicated molecules, the likelihood that RNA arose on its own is minimal.Bloom's

Question 8

Which feature is lacking in the cell wall of Archaea that will distinguish them from the bacteria?

Accepted Answer

Archaea lack peptidoglycan in their cell walls which will distinguish them from the bacteria. Phospholipids, proteins and polysaccharides are found in the cell walls of both Archaea and bacteria.Bloom's

Question 9

Which term does NOT apply to the first protocell?

Accepted Answer

The first protocells would have a ready supply of food molecules available in the ocean and were therefore, likely to be heterotrophs. With no oxygen present in the atmosphere fermentation would have been the only option for energy production. A cell must, by definition, have a membrane to separate it from the surrounding environment and the first cells would have been single cells with multicellular forms evolving much later.Bloom's

Question 10

What feature enables the Archaea to survive in harsh environments?

Accepted Answer

The cell wall is the main feature that enables the Archaea to survive in harsh environments. They do not possess a nucleus. Their metabolism, and reproductive capabilities are not the main feature that enables them to survive in harsh environments. Archaea do not form multicellular organisms.Bloom's

Question 11

Which of these would have been most likely to develop only after the formation of a true cell?

Accepted Answer

The ocean at this time contained a ready supply of preformed food so it is likely that heterotrophs were the first to evolve. Autotrophs would have evolved later.Bloom's

Question 12

Which of the following is a benefit of microbes?

Accepted Answer

All of these are benefits of microbes.Bloom's

Question 13

Through molecular interaction of the macromolecules in the primitive ocean,the self-replicating system of ____ evolved.

Accepted Answer

According to the RNA-first hypothesis, RNA would have been the first genetic material to evolve, and the first true cell would have had RNA genes. These genes would have directed and enzymatically carried out protein synthesis, as in ribozymes. Perhaps, with time, reverse transcription gave rise to DNA genes. Once DNA genes existed, they may have specified proteins.Bloom's

Question 14

Compare the Domains of Archaea and Eukarya in regards to their features.

Accepted Answer

The answer of Compare the Domains of Archaea and Eukarya...

Question 15

The fact that a nucleic acid is a very complicated molecule suggests that

Accepted Answer

Nucleotides are complex molecules that require a complex system of other molecules to maintain and replicate them and to produce proteins. They therefore, could not have arisen without first the machinery to produce and maintain them.Bloom's

Question 16

Which statement is NOT true about a protocell?

Accepted Answer

Before the first true cell arose, there would likely have been a protocell, a structure that had a lipid-protein membrane and carried on energy metabolism. Fox has shown that if lipids are made available to microspheres, the two tend to become associated, producing a lipid-protein membrane. Coacervate droplets have a tendency to absorb and incorporate various substances from the surrounding solution.Bloom's

Question 17

Which type of nutrition is believed to have come first?

Accepted Answer

The first protocells would have a ready supply of food molecules available in the ocean and were therefore, likely to be heterotrophs.Bloom's

Question 18

What general feature is necessary to consider an organism a microbe?

Accepted Answer

Microbes are generally small enough that a microscope is required to see them. All of the other features are not necessarily found in microbes.Bloom's

Question 19

Which of the following organisms is considered a microbe?

Accepted Answer

Bacteria is considered a microbe.Bloom's

Question 20

Some twentieth-century authors wrote that the earliest protocells would have to be autotrophs.This concept appears to be

Accepted Answer

It has been suggested that the protocell likely was a heterotroph, an organism that takes in preformed food. During the early evolution of life, the ocean contained abundant nutrition in the form of small organic molecules. This suggests that heterotrophs preceded autotrophs, organisms that make their own food.Bloom's

Quiz 28: Microbiology