Question

QUESTION 1

1. To study how proteins fold, scientists must be able to purify the protein of interest, use solvents like urea to denature the folded protein, and observe the process of refolding at successive time points. What is the effect of the solvents used in the denaturation process?

   	a.	The solvents break all noncovalent interactions.
   	b.	The solvents break all covalent interactions.
   	c.	The solvents create a new folded conformation.
   	d.	The solvents break some of the noncovalent interactions, resulting in a misfolded protein.

1 points   

QUESTION 2

1. Alpha-helices are important for which of the following types of proteins? (choose all correct answers)

   	a.	Ion channels
   	b.	DNA double helix
   	c.	Coiled-coil proteins
   	d.	Amyloid structures

1 points   

QUESTION 3

1. Choose all amino acids that are positively charged and non-polar.

   	a.	Lysine
   	b.	Phenylalanine
   	c.	Glutamic acid
   	d.	All of the above.
   	e.	None of the above.

1 points   

QUESTION 4

1. Which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains?

   	a.	electrostatic interactions
   	b.	hydrogen bonds
   	c.	van der Waals attractions
   	d.	hydrophobic forces

1 points   

QUESTION 5

1. Which of the following levels of protein structure involves the interaction of more than one polypeptide chain into a three-dimensional structure?

   	a.	quaternary
   	b.	secondary
   	c.	tertiary
   	d.	primary

1 points   

QUESTION 6

1. A stretch of amino acids in a polypeptide chain that is capable of independently folding into a defined structure is called a

   	a.	domain.
   	b.	subunit.
   	c.	ligand.
   	d.	backbone.

1 points   

QUESTION 7

1. Which amino acids would mostlikely be on the inside of a properly folded, globular protein? (choose all correct answers)

   	a.	Glutamine
   	b.	Tryptophan
   	c.	Proline
   	d.	Tyrosine

1 points   

QUESTION 8

1. Which of the following is FALSE about molecular chaperones?

   	a.	They help streamline the protein-folding process by making it a more efficient and reliable process inside the cell.
   	b.	They can isolate proteins from other components of the cells until folding is complete.
   	c.	They can interact with unfolded polypeptides to promote energetically unfavorable folding.
   	d.	They assist polypeptide folding by helping the folding process follow the most energetically favorable pathway.

1 points   

QUESTION 9

1. If protein folding is determined by the sequence of amino acids in the polypeptide chain, why are chaperone proteins needed to assist folding in the cell?

   	a.	Proteins constantly unfold and refold.
   	b.	Certain proteins easily aggregate with other proteins.
   	c.	Some proteins cannot fold on their own.
   	d.	Protein folding is energetically unfavorable.

1 points   

QUESTION 10

1. The correct folding of proteins is necessary to maintain healthy cells and tissues. The presence of unfolded proteins are associated with some neurodegenerative disorders as Alzheimer’s disease, Huntington’s disease, and Creutzfeldt–Jakob disease. What happens to these disease-causing, unfolded proteins?

   	a.	They form protein aggregates.
   	b.	They form an aggregate of alpha helices.
   	c.	They refold correctly and function normally.
   	d.	They are quickly degraded and cleared from the cell.

Answer 1

Answer=

QUESTION 1

To study how proteins fold, scientists must be able to purify the protein of interest, use solvents like urea to denature the folded protein, and observe the process of refolding at successive time points. the effect of the solvents used in the denaturation process is

a.The solvents break all noncovalent interactions

Explanation - When we treat protein with urea,urea interacts directly as well as indirectly with protein.

In direct mechanism urea either directly interacts with protein backbone via hydrogen bonding and other electroststic interactions such as van der waals attractions ,causes the protein to denature.

In indirect mechanism ,urea disrupt the structure of water molecule, thus making hydrophobic groups more readily solvated .

in this way hydrophobic interaction,electrostatic attraction ,hydrogen bonding and van der waals attractions are most important noncovalent interactions break by urea causes protein denaturation.

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2.Alpha-helices are important for which of the following types of proteins

a.Ion channel = are made up of alpha helix.the potassium ion channel is made up of four alpha subunits.the 6-helix bundle is also found in calcium channel.

c.Coiled-coil proteins = A coiled coil is a structural motif in proteins in which 2-7 alpha-helices are coiled together like the strands of a rope.

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3.amino acids that are positively charged and non-polar.

e.None of the above

Explanation - Lysine is positively charged amino acid but it is not nonpolar,it has a polar side chain.

phenylalanine has a nonpolar side chain but it is not positively charged amino acid.

glutamic acid is negatively charged amino acid.

hence the correct answer is none of the above.

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4.Which type of noncovalent interaction can involve either the polypeptide backbone or amino acid side chains

b.hydrogen bonds

Explanation = Hydrogen bond is a type of noncovalent interaction which is formed in polypeptide backbone.The hydrogen bond is formed in between the N-H and C=O groups in the polypetide backbone,without involving the side chains of the amino acids.