Question 1

Which of the groups below is capable of only hydrophobic interactions? Explain your answer.Which is capable of only hydrophilic interactions? Explain your answer.

Accepted Answer

The answer of Which of the groups below is capable...

Question 2

Which amino acid is most likely to be found in the core of a protein?

Accepted Answer

Methionine contains a hydrophobic (nonpolar) side chain and is often found buried in the hydrophobic core of proteins, away from the aqueous environment.

Question 3

You treat a partially purified preparation of protein with a reagent that breaks bonds between sulfur atoms.Which level(s)of protein structure are likely to be affected the most?

Accepted Answer

The answer of You treat a partially purified preparation of...

Question 4

You are a crew member on the starship Enterprise.Your responsibilities include investigation of biological life forms.You take out your tricorder after landing on the planet Yamihere and find a number of organisms,all of which contain DNA that follows the nitrogenous base pairing rules you are familiar with on Earth.For one species,the following relationships hold for the organism's DNA.
  How many moles of guanine are present?
How many moles of thymine are present?
How many moles of uracil are present?
You isolate DNA from another organism living on the surface of Yamihere and find that it contains all the bases normally found in DNA,but does not obey the pairing rules.Can you explain these strange results?

Accepted Answer

The answer of You are a crew member on the...

Question 5

An enzyme is placed in a solution containing urea.Assuming that this protein contains no disulfide linkages,is it reasonable to suspect that it will be totally denatured by the treatment? How could you know that the enzyme has,in fact,been denatured? Why does the urea denature the tertiary structure of the enzyme?

Accepted Answer

The answer of An enzyme is placed in a solution...

Question 6

Not all proteins are able to renature.Some proteins when exposed to heat or some other denaturing treatment are irreversibly denatured.What is an example of such a protein?

Accepted Answer

The answer of Not all proteins are able to renature.Some...

Question 7

How do amino acids like hydroxylysine and thyroxine,which are not among the 20 amino acids that are inserted into proteins,get into proteins?

Accepted Answer

The answer of How do amino acids like hydroxylysine and...

Question 8

The $\beta$ -pleated sheet is characterized by orientation of ______ the molecular axis.

Accepted Answer

The F1F1F1S1F1F1F10-pleated sheet is characterized by hydrogen bonds perpendicular to the molecular axis. This is because the hydrogen bonds form between the peptide bonds of adjacent strands, creating a zigzag pattern that runs perpendicular to the axis.

Question 9

What level of structure in DNA would be disrupted by a reagent that breaks apart hydrogen bonds?

Accepted Answer

The answer of What level of structure in DNA would...

Question 10

You are working with an enzyme altase that you denature in the presence of urea.If altase were denatured no further by the addition of mercaptoethanol,what would that suggest to you about the enzyme?

Accepted Answer

The answer of You are working with an enzyme altase...

Question 11

Would all proteins be likely to require exposure to mercaptoethanol in order to accomplish full denaturation? If not,what trait would a protein that did not require mercaptoethanol possess?

Accepted Answer

The answer of Would all proteins be likely to require...

Question 12

Mammals lack the enzyme that hydrolyzes cellulose.Yet many mammals are herbivores and they eat grass and other plant material for nutrition.How can this be,given that they cannot digest the food they are eating?

Accepted Answer

The answer of Mammals lack the enzyme that hydrolyzes cellulose.Yet...

Question 13

Tertiary structure in DNA is also known as ________.

Accepted Answer

Tertiary structure in DNA refers to the overall three-dimensional structure of the DNA molecule, which includes supercoiling. Primary structure refers to the sequence of nucleotides in the DNA strand, while double helix refers to the basic structural unit of DNA. F1F1F1S1F1F1F10-helix is not a known term for DNA structure.

Question 14

DNA is isolated from two different species.Both DNA samples are found to be the same size.One of the DNA samples has a G+C/A+T ratio of 2.0 and the other 2.5.Which DNA sample has a higher G+C content? Which sample contains the smallest number of H bonds between strands? Which DNA sample would be easiest to denature?

Accepted Answer

The answer of DNA is isolated from two different species.Both...

Question 15

Which of the following tripeptides would be most likely to be soluble in an organic (hydrophobic)solvent like benzene: N - phenylalanine - alanine - glutamine - C,N - leucine - alanine - lysine - C,N - proline - phenylalanine - leucine - C,N - arginine - lysine - proline - C,N - glutamate - aspartate - glycine - C? Explain your answer.

Accepted Answer

The answer of Which of the following tripeptides would be...

Question 16

What is now thought to have been the genetic material in the first living organisms on Earth?

Accepted Answer

The RNA World Hypothesis suggests that RNA was the genetic material in the first living organisms on Earth. RNA can both store genetic information and catalyze chemical reactions, making it a possible candidate for the first self-replicating molecule. While DNA is now the primary genetic material in living organisms, it is believed to have evolved from RNA. Protein and polypeptides are important components of living organisms, but they are not believed to have been the genetic material in the first living organisms.

Question 17

Which of the following is a nucleotide?

Accepted Answer

A nucleotide is composed of a nitrogenous base, a sugar, and a phosphate group. Adenine is a nitrogenous base and ribose is a sugar, so D (adenine + ribose + phosphate) is the only choice that includes all three components of a nucleotide.

Question 18

Proteins are often composed of two or more distinct modules that fold up independently of one another.They often represent parts of a protein that function in a semi-independent manner.These modules are called ______.

Accepted Answer

The term "protein motifs" generally refers to short amino acid sequences that are conserved across multiple proteins and have a specific function. The term "functionals" is not commonly used in the context of protein structure. The term "dominoes" does not accurately describe the modular nature of protein domains. Therefore, the best choice is C, domains.

Question 19

What level of structure in proteins is held together by intermolecular R group interactions?

Accepted Answer

The answer of What level of structure in proteins is...

Question 20

What type of protein secondary structure is characterized as being highly extensible because of its coiled structure?

Accepted Answer

The alpha helix is characterized by a coiled structure that is highly extensible under tension because the helix can uncoil without breaking bonds. The other options listed (beta-pleated sheets, double helix, and supercoiling) do not have the same degree of extensibility as the alpha helix.

Quiz 2: The Chemical Basis of Life