Mastering Biology: Chapter 3 Part B

Some regions of a polypeptide may coil or fold back on themselves. This is called __________, and the coils or folds are held in place by __________. tertiary structure ... covalent bonds tertiary structure ... hydrogen bonds secondary structure ... peptide bonds primary structure ... covalent bonds secondary structure ... hydrogen bonds

secondary structure... hydrogen bonds

Interactions between the side chains (R groups) in a polypeptide are most important in stabilizing which of the following? quaternary structure tertiary structure secondary structure primary structure

tertiary structure

Describe the 4 levels of proteins

-primary: the order of amino acids in the polypeptide chain -secondary: localized regions of alpha helices and beta pleated sheets -tertiary: the overall three-dimensional shape of a polypeptide, stabilized by interactions between R groups -quaternary: the association of more than one polypeptide subunit into a functional protein.

Which of these illustrates the secondary structure of a protein? (see mastering question 1)

Coils and folds

What could happen if a mutation in a gene caused a hydrophobic amino acid in a polypeptide to be replaced by a hydrophilic amino acid? -The new amino acid would not form the same interactions with hydrophobic R groups, and the protein's shape would likely be affected. -The shape of the protein would not be affected if only one amino acid in the primary structure is changed. -There would be no effect as long as the protein had quaternary structure, because primary structure does not affect that level. -The hydrophilic amino acid could not form the proper peptide bond in its new location, so both the shape and function of the protein would be affected.

The new amino acid would not form the same interactions with hydrophobic R groups, and the protein's shape would likely be affected.

Your body contains tens of thousands of different proteins, each with a specific structure and function. The unique three-dimensional shape of each of these diverse proteins is based on several superimposed levels of structure. Which of the following statements is an accurate description of proteins? -The primary structure of a protein is the order of amino acids in a polypeptide, as coded for in the DNA of a gene. -The 20 amino acids found in proteins differ in the composition of their R groups, which may be either polar or charged. -Secondary structures, which include the alpha helix or beta pleated sheet, are held together by interactions between R groups. -Tertiary structure is the overall shape of a polypeptide, which may be stabilized by hydrophobic interactions, hydrogen bonds, ionic bonds, and peptide bonds. -Quaternary structure is only found in proteins that have four identical polypeptide subunits.

The primary structure of a protein is the order of amino acids in a polypeptide, as coded for in the DNA of a gene.

These figures show the four levels of protein structure: primary, secondary, tertiary, and quaternary structure. Which level of protein structure is characteristic of some, but not all, proteins? Secondary level of protein structure Quaternary level of protein structure Tertiary level of protein structure

Quaternary level of protein structure

Changing a single amino acid in a protein consisting of 433 amino acids would -sometimes alter the primary and tertiary structure of the protein but always alter its function. -always alter the primary structure of the protein and sometimes alter its tertiary structure or function. -always alter the primary structure of the protein but never alter its tertiary structure or function. -always alter the primary and tertiary structure of the protein but never alter its function.

always alter the primary structure of the protein and sometimes alter its tertiary structure or function.

Proteins are polymers of _____. hydrocarbons amino acids CH2O units glycerol nucleotides

amino acids

There are 20 different amino acids. What makes one amino acid different from another? different side chains (R groups) attached to an α carbon different side chains (R groups) attached to the carboxyl carbon different asymmetric carbons different side chains (R groups) attached to the amino groups

different side chains (R groups) attached to an α carbon

The secondary structure of a protein results from _____. hydrophobic interactions ionic bonds bonds between sulfur atoms peptide bonds hydrogen bonds

hydrogen bonds

What type of bond joins the monomers in a protein's primary structure? ionic hydrophobic S - S hydrogen peptide

peptide

Tertiary structure is NOT directly dependent on _____. hydrophobic interactions bonds between sulfur atoms ionic bonds peptide bonds hydrogen bonds

peptide bonds

Which bonds maintain the primary structure of a protein? peptide bonds ionic bonds hydrogen bonds disulfide bonds

peptide bonds

The α helix and β pleated sheet are examples of which level of protein structure? primary secondary tertiary quaternary primary, secondary, tertiary, and quaternary

secondary

Lactase is an enzyme composed of a single polypeptide that hydrolyzes the disaccharide lactose to produce monosaccharides. The optimal pH for lactase activity is 6. Transfer of lactase to pH 5 results in a substantial decrease in enzyme activity, likely due to the disruption of: the secondary, tertiary, and quaternary structure of the enzyme. only the primary structure of the enzyme. the primary and secondary structure of the enzyme. the secondary and tertiary structure of the enzyme.

the secondary and tertiary structure of the enzyme.