Chapter 3

Upon chemical analysis, a particular protein was found to contain 438 amino acids. How many peptide bonds are present in this protein?

437

What two functional groups are present in every amino acid?

An amino group and a carboxyl group

Enzymes function best at particular temperature and pH conditions. What is the most likely enzyme to be present in a bacterium found in a hot water vent in an acidic current?

Enzyme B, which functions best at a pH of 3 and a temperature of 90o Celsius

Which of the following amino acids is hydrophobic?

Glycine

What bond type is responsible for the secondary structure of a protein?

Hydrogen

Which of the following is true of the peptide bond?

It is a covalent bond formed via a condensation reaction.

Which of the following amino acids is more likely to come together in aqueous solutions?

Leucine

During the denaturation of ribonuclease, which level of protein structure was maintained?

Only the primary protein structure was maintained.

What is the first step in the chemical evolution theory?

Organic compounds formed from chemicals present in the atmosphere and oceans of ancient Earth.

Which statement about prions is true?

Prions cause changes in the shape of normal proteins that can lead to cell death.

Proteins are critical in living organisms. What is one example of the many important functions of proteins in organisms?

Proteins impart mobility to entire cells and molecules within cells.

Which level of protein structure results from five types of interactions involving the side chains—ionic bonds, hydrogen bonds, van der Waals interactions, covalent bonds, and hydrophobic interactions?

Tertiary

In the diagram of a protein structure, letter (b) best represents which of the following descriptions?

The formation of α-helices and β-pleated sheets

Which statement best describes the R groups or side chains of amino acids?

The nature of R groups or side chains determines how soluble each amino acid is in water.

What may have aided the polymerization of amino acids into peptides in the oceans of early prebiotic Earth?

The presence of mineral surfaces for the amino acids to adhere to

In the diagram of protein structure, letter (a) best represents which of the following descriptions?

The sequence of amino acids in a polypeptide

The chemical structure of valine and asparagine differ in which of the following?

The side chain (R group)

At which step of chemical evolution did life become possible?

When a self-replicating molecule evolved

The linear order of amino acids in a protein helps determine which level of protein structure?

all levels of protein structure

A hydrophobic R group would most likely be found __________.

buried in the interior of a protein

Aspartate and glutamate are two amino acids that are highly soluble in water. This is best explained by the fact that they __________.

have electrical charged side chains or R chains

Sickle-cell anemia results when valine replaces glutamate at position six of the β-globin subunit of hemoglobin. The sickling seen in red blood cells with the defective hemoglobin subunit results from a change in the

primary structure of hemoglobin

Protein function is dependent upon its shape. Some proteins may misfold, which interferes with their normal function. Infectious disease-causing agents caused by protein misfolding are called ________.

prions

Researchers doubt that proteins were the first living entity because __________.

protein do not serve as a good template for replication

Substrates are also known as ___________.

reaction

Many proteins fold spontaneously because _______.

the bonds that form secondary and tertiary structure are energetically favorable

In the diagram of a protein structure, letter (c) best represents which of the following descriptions?

the overall three-dimensional shape of polypeptide

In the diagram of a protein structure, letter (d) best represents which of the following descriptions?

the shape produced when two or more polypeptides associate to form a functional protein

A chemical that breaks disulfide bonds might destroy which level of protein structure?

the tertiary structure

Which of the following statements is true regarding the amino acids that have R groups or side chains that consist solely of carbon and hydrogen atoms?

they rarely participate in chemical reactions