Biochemistry Chapter 2 test bank

The term quaternary with respect to protein structure means

A multisubunit structure

How does a protein's amino acid sequence influence tertiary structure?

A protein will spontaneously fold into a three dimensional structure determined by the amino acid sequence

Key properties of proteins include:

A wide range of functional groups, an ability to possess either rigid or flexible structures as dictated by functional requirements, the ability to interact with other proteins.

The (blank) Beta sheet structure occurs when the two strands are oriented in same direction

Antiparallel

Disulfide bonds in proteins can be reduced to free sulfhydryl groups by reagents such as

Beta Mercaptoethanol

At a pH of 12, what charged groups are present in glycine?

COO-

Proteins function as:

Catalysts

What are some modifications that proteins acquire?

Cleavage and trimming of the protein, addition of carbohydrate groups, phosphorylation of certain groups

Describe some of the features of an alpha helix

Coil stabilized by intrachain hydrogen bonds between the carbonyl oxygen of a residue and the amide hydrogen of the 4th residue away. There are 3.6 amino acids per turn, the hydrogen bonds are between amino acid residues that have two intervening residues. These amino acid residues are found on the same side of the coil. The helix is almost always right-handed.

A protein is considered to be (blank) when it is converted into a randomly coiled structure without its normal activity

Denatured

Every third residue of the protein collagen is

Glycine

Why is the peptide bond planar?

It exhibits partial double-bond character, preventing rotation.

Name three amino acids that can be positively charged at a neutral pH

Lysine, arginine, and histidine

The amino acid that contains a sulfur atom and is considered hydrophbic is called

Methionine

What charged groups are present in glycine at a pH of 7?

NH3+, COO-

Where are Omega and Beta turns and loops often found?

On the surface of proteins

In the following peptide, which amino acid is the N-terminus: Phe-Ala-Gly-Arg

Phe

Which of the following amino acid residues would most likely be buried in the interior of a water soluble, globular protein?

Phe

What are the three aromatic amino acids?

Phenylalanine, tyrosine, and tryptophan

(Blank) refers to the spatial arrangement of subunits and the nature of their interactions

Quaternary structure

What does the modification involving the attachment of acetyl groups to the amino terminus of a protein do?

The acetylation of the amino termini of a protein is to make these proteins more resistant to degradation.

How does the protein backbone add to structural stability?

The protein backbone contains the peptide bond, which has NH molecule and C=O groups. Hydrogen-bond formation between the hydrogen on the nitrogen and the oxygen support the protein conformation

What is the hydrophobic effect as it relates to proteins?

The three dimensional structure of a water-soluble protein is stabilized by the tendency of hydrophobic groups to assemble in the interior of the molecule.

What do the amino acids Tyr, asn, and thr, have in common?

They are polar

The configuration of most alpha carbon atoms of amino acids linked in a peptide bond is

Trans

Agents such as (blank) and guanidine HCl denature proteins by disrupting the noncovalent interactions

Urea

Which amino acid side chains are capable of ionization?

aspartate, glutamate, histidine, cysteine, tyrosine, lysine, arginine

Which amino acids contain sulfur?

cysteine and methionine