bs 161 hw6

How many water molecules would be produced in making a polypeptide that is 14 amino acids long?

13

How many carbons are contained in this skeleton structure of Aspartate?

4

What causes denaturation of a protein?

Acidic environments (i.e., pH < 2). High heat (i.e., >212 F or 100ºC) Basic environments (i.e., ph > 9)

Using the structures of amino acids (you will need to look at pp. 73 (Fig. 4.2) in the textbook or look this up online), determine which one of the following amino acids is MOST likely to participate in hydrogen bonding with water?

Asparagine

New amino acids add to a peptide at its:

C terminus.

At physiological pH (i.e., pH 7), the ionized state of the carboxyl (COOH) in the R group of aspartic acid is:

COO^-

The image shows the binding pocket of a protein (on the left) to a small molecule on the right. (Please note that the complete R-group is not shown.) Which of the following changes would be most likely to disrupt the binding of the small molecule?

Changing Arg to Val would disrupt ionic bonding.

Which of the following would affect the secondary structure of a protein?

Disruption of the hydrogen bonds that hold different regions of the poly-peptide backbone together.

You are studying a protein with aspartic acid in a position that is important for stabilizing its structure. If this aspartic acid changes to a different amino acid due to a mutation, which of the following amino acid substitutions would be the MOST likely to allow the protein to fold normally?

Glutamic acid

Which one of the following can contribute to a protein's tertiary structure?

Hydrogen bonds Covalent bonds Ionic bonds

The image shows a tight grouping of specific amino acids that formed during protein folding. Based on the properties of these amino acids, what interaction likely accounts for this formation? Phe Pro Met Leu Ile Gly

Hydrophobic effect

What is wrong with this diagram of the secondary structure in a polypeptide chain?

It has two amino ends.

Which of the following amino acids has a non-polar R group?

Leucine

At physiological pH, the ionized state of the amino (NH2) group in the R group of lysine is:

NH3^+

The function of a protein is dependent upon the shape into which the chain of amino acids folds. Many noncovalent interactions are responsible for maintaining the protein's shape. Assume you have isolated a protein from an organism in its proper shape, and you have treated it with an enzyme that selectively targets and breaks only the peptide bonds in the proteins. Would the protein retain its shape under these conditions?

No; while the noncovalent bonds determine the shape of a protein, the peptide bonds are required to hold the amino acids together.

Which of the following amino acids is most likely to be found on the outside of a properly folded protein in the cytoplasm?

Serine

Based on these statements pick the most correct answer. Statement 1 - All polypeptides a have tertiary structure. Statement 2 - All proteins have a quaternary structure

Statement 1 is true, but statement 2 is false

A burn caused by boiling water causes proteins inside your cells to lose their functions. Explain why the high temperature causes this to happen.

The increased temperature disrupts weak interactions such as hydrogen bonding, which causes the proteins to lose their tertiary structures and abilities to bind specific molecules.

Which one of the following is NOT a component of an amino acid?

Triphosphate group

Which of the following amino acids has an aromatic R group?

Tryptophan

T or F: Most proteins retain metabolic activity when denatured.

false

Which pair of amino acid side chains pictured here would most likely form an ionic bond to stabilize tertiary structure in a protein? Why?

ii and iii because they have opposite charges.

The R-group of a basic amino acid is:

positively charged at pH 7 and thus could bind DNA.

Peptide bonds form between amino acids to stabilize the __________ structure of a protein.

primary

When a peptide bond is created between two amino acids:

the carboxyl group of the first amino acid is joined to the amino group of the second.

T or F: Amino acids with hydrophobic R groups are most often found buried in the interior of folded proteins.

true

T or F: The individual polypeptide chains in a multi-subunit protein each have their own primary, secondary, and tertiary structure.

true

T or F: The sequence of amino acids in a protein is referred to as its primary structure.

true

Two major types of protein secondary structures are referred to as:

α helix and β sheet.

In a ribbon model of a polypeptide, broad arrows indicate:

β sheets