Question 1

What are some possible explanations for the branched structure of glycogen?

Accepted Answer

The answer of What are some possible explanations for the...

Question 2

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 3

It is thought that most human diseases leave telltale patterns among the thousands of proteins present in the blood or other bodily fluids.It was hoped that analysis of the proteins present in the blood would help in the diagnosis of human disease; however,thus far,searches for these proteins in blood or bodily fluids have been largely unsuccessful and their use in diagnostics largely unreliable.What are these telltale patterns of proteins called?

Accepted Answer

The answer of It is thought that most human diseases...

Question 4

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 5

Which of the following is a nucleotide?

Accepted Answer

A nucleotide consists of three components: a nitrogenous base, a sugar molecule, and one or more phosphate groups. Adenine is a nitrogenous base, ribose is a sugar molecule, and phosphate is a phosphate group. Therefore, D (adenine + ribose + phosphate) is the only answer choice that correctly identifies a nucleotide.

Question 6

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

Accepted Answer

The F1F1F1S1F1F1F10-helix is characterized as being highly extensible because of its coiled structure.

Question 7

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 8

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 9

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

Accepted Answer

The F1F1F1S1F1F1F10-pleated sheet is characterized by H bonds perpendicular to the molecular axis. This orientation creates the pleated appearance and stability of the sheet.

Question 10

Many so-called temperature-sensitive mutations have been discovered in a wide variety of organisms.These are proteins that are non-functional at higher temperatures,while,at lower temperatures (often just a few degrees lower),they function normally.For example,the coloration patterns in Siamese Cats arise from a temperature-sensitive mutation.An enzyme required for the synthesis of dark pigment is unable to function in areas close to the body where normal physiological temperatures prevail.However,at the tips of the ears,paws,the tip of the tail and other extremities where the temperature is slightly lower,the enzyme works correctly and dark pigment is produced.What is happening at the molecular level that explains this?

Accepted Answer

The answer of Many so-called temperature-sensitive mutations have been discovered...

Question 11

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 12

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 13

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

These distinct modules that fold up independently of one another and represent parts of a protein that function in a semi-independent manner are called domains. Protein motifs refer to conserved amino acid sequences that are found within proteins and often have a specific function or structural role. "Functionals" and "dominoes" are not commonly used terms in protein biochemistry.

Question 14

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

Hydroxylysine and thyroxine are formed by post-translational modifications of the R groups of standard amino acids after they have been incorporated into the polypeptide chain.

Question 15

You are studying a protein.It binds to elongating polypeptide chains as they emerge from an exit channel within the ribosome's large subunit.It appears to prevent partially formed or nascent polypeptides from binding to other proteins in the cytosol,which might cause them either to aggregate or misfold.What kind of proteins is this likely to be? Another protein you are studying picks up larger proteins from Hsp70 family proteins.It is a cylindrical protein complex that contains chambers in which newly synthesized polypeptides can fold without interference from other cellular macromolecules.What is this protein called?

Accepted Answer

The answer of You are studying a protein.It binds to...

Question 16

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 17

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

Accepted Answer

Methionine contains a sulfur atom in its side chain, making it hydrophobic and allowing it to interact favorably with other hydrophobic residues in the core of a protein. This makes it more likely to be found in the core of a protein, compared to polar or charged residues like asparagine, serine, threonine, or glutamic acid.

Question 18

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 19

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

Accepted Answer

Quaternary structure is held together by intermolecular R group interactions.

Question 20

Scientists have sequenced proteins by using specific proteases to "clip" a purified protein preparation between two specific amino acids,thus forming a number of moderately sized fragments; they have used acid hydrolysis to produce smaller fragments.Each fragment can then be sequenced by breaking the moderate fragments into dipeptides that are easily sequenced.The fragments below are obtained after the initial enzymatic cleavages.Can you deduce the sequence of the original polypeptide? (HINT: the original cleavages at specific locations differ depending on which proteolytic enzyme was used to create each fragment; this causes an overlap in the fragments' sequences.)The final polypeptide should have 18 amino acid residues.

Accepted Answer

The answer of Scientists have sequenced proteins by using specific...

Quiz 2: The Chemical Basis of Life