BIOLOGY CHAPTER 3

Which of the following statements about the formation of polypeptides from amino acids is true?

A bond forms between the carboxyl functional group of one amino acid and the amino functional group of the other amino acid.

In proteins, secondary, tertiary, and quaternary levels of structure depend on primary structure. Which of the following most accurately lists elements of any protein's primary, secondary, tertiary, and quaternary structure, in that order?

Amino acid sequence, hydrogen bonding between backbone groups, overall shape of a single polypeptide, and combinations of tertiary structures

Which of the following is not attached to the central carbon atom in an amino acid?

An oxygen

structural

Arrow A is indicating a(n) _____ protein.

receptor

Arrow D is indicating a _____ protein.

At which bond would water need to be added to achieve hydrolysis of the peptide, back to its component amino acids?

C the 3rd bond

Which part of an amino acid is always acidic?

Carboxyl functional group

Biological activity DIRECTLY involve proteins?

Changing the shape of a cell. Defending cells against viruses. Breaking food polymers into smaller molecules. Sensing light.

You have just sequenced a new protein found in mice and observe that sulfur-containing cysteine residues occur at regular intervals. What is the significance of this finding?

Cysteine residues are involved in disulfide bridges that help form tertiary structure.

What enzymes help separate the 2 strands of nucleotides on DNA? What bonds do they break?

Helicase and hydrogen bonds

Nonpolar amino acid residues are typically found in the interior of globular proteins like trypsin. Which chemical force is most directly responsible?

Hydrophobic interactions

At about pH 7 in most cells, what happens to the amino R-group on an amino acid?

It acts as a base and gains a proton, giving it a positive charge.

Which monomers make up RNA?

Nucleotides

Name the 3 parts of a DNA nucleotide

Phosphate sugar and nitrogen base

Which of the following statements about protein primary structure is true?

Primary structure is produced by the unique sequence of amino acids in a protein.

Which polymers are composed of amino acids?

Proteins

Which characteristics make proteins the most versatile macromolecules in cells in terms of functional capabilities?

Proteins have diverse structures, diverse chemical properties, and flexible shapes.

Most protein enzymes catalyze only one specific chemical reaction effectively. What feature of protein structure is most directly responsible for this specificity?

The specific geometry and types of amino acids in the active site

transport

This animation illustrates the functioning of a _____ protein.

True or false? Enzymes in the digestive tract catalyze hydrolysis reactions.

True

How did Rosalind Franklin contribute to determining the structure of DNA?

Used x-ray detraction to determine the shape

More than one shape is possible for a protein and different shapes function differently or not at all

What features of protein folding and function are revealed by calmodulin and prions?

polymerization

a chemical process that combines several monomers to form a polymer or polymeric compound

monomers

a chemical subunit that serves as a building block of a polymer.

dipeptide

a molecule consisting of two amino acids

macromolecule

a very large organic molecule composed of many smaller molecules

name 2 purines

adenine and guanine

Proteins are polymers of _____.

amino acids

Which class(es) of amino acids possess side chains that would be unable to form hydrogen bonds with water?

amino acids with nonpolar side chains

By convention, biologists write the sequence of amino acids in a polypeptide in which direction?

amino- to carboxy-terminus

What two functional groups are present on every amino acid?

an amino group and a carboxyl group

Proteins help cells with which task(s)?

catalysis signaling transport

Proteins in biological systems _____.

catalyze reactions

secondary structure

coiling chain an alpha helix or beta pleated sheet due to Hydrogen bonding

During protein synthesis, the peptide bond between amino acids is formed by the process of _____.

condensation

oligopeptide

consists of up to 20 amino acids

Secondary structure

describes the alpha-helices and beta-sheets that are formed by hydrogen bonding between backbone atoms located near each other in the polypeptide chain

catalysis

enzymes speed up chemical reactions

The secondary structure of proteins results because of _____ bonding between atoms in the protein's backbone.

hydrogen

The secondary structure of a protein results from _____.

hydrogen bonds

quaternary structure

if protein is composed of more than one polypeptide

Defensive proteins are manufactured by the _____ system.

immune

Where is the information that directs different polypeptides to fold into different shapes?

in the primary structure

Tertiary structure

is achieved when a protein folds into a compact, three-dimensional shape stabilized by interactions between side-chain R groups of amino acids

Quaternary structure

is the result of two or more protein subunits assembling to form a larger, biologically active protein complex

Primary structure

is the sequence of amino acids in a protein

polypeptide

long chain of amino acids that makes proteins

What causes mad cow disease and other such spongiform encephalopathies?

misfolded proteins known as prions

polymers

molecules that are chains of repeating units; proteins and DNA are examples.

What are the subunits called that make up DNA?

nucleotides

Which of these does NOT contain a structural protein?

ovalbumin

What type of bond joins the monomers in a protein's primary structure?

peptide

In a polypeptide, what bonds are responsible for the primary structure?

peptide bonds

Tertiary structure is NOT directly dependent on _____.

peptide bonds

What makes up the backbone of the DNA molecule?

phosphates and sugars (hold together by strong covalent bonds)

When polymerization of a protein is complete, but a protein is still completely linear, what is the highest level of structure in the protein?

primary

What level of protein structure describes an amino acid sequence such as Ala-Gly-Ser-Val-Glu-Glu-Glu-Ala-His...?

primary structure

You are studying a protein that is shaped like a doughnut. The shape is a function of which level(s) of protein structure?

primary, secondary, and tertiary

What is the difference between a purine and a pyrimidine?

purine has 2 rings. pyrimidine has 1

At what level of protein structure do the α and β protein subunits come together to catalyze the hydrolysis reaction?

quaternary structure

tertiary structure

refers to the overall 3D structure of a protein and how it folds; H bonds, ionic bonds, polar interactions, non polar interactions, disulfide bridge

The alpha-helix is a component of __________ protein structure.

secondary

At what level of protein structure do the chains of amino acids fold into an α-helical structure?

secondary structure

What makes up the sides of a DNA molecule?

sugars and phosphates

At what level of protein structure do β-sheets of amino acids and α-helices, located at a distance from each other along the length of a polypeptide chain, come together to form a globular protein?

tertiary structure

primary structure

the first level of protein structure; the specific sequence of amino acids making up a polypeptide chain by covalent

What makes up the steps of a DNA molecule?

the nitrogen bases

What distinguishes these molecules?

the number of carbon atoms in the side chains functional groups found in the side chains

Which of the following parts of an amino acid vary among different amino acids?

the side chain, or R group

name 2 pyrimidines

thymine and cytosine

The tertiary structure of a protein is the _____.

unique three-dimensional shape of the fully folded polypeptide