Question 1

Which of the above pairs of side chains could be involved in a hydrophilic interaction?

Accepted Answer

The answer of Which of the above pairs of side...

Question 2

What is the functional group that links amino acids together to form proteins?

Accepted Answer

The functional group that links amino acids together to form proteins is an amide bond, which is formed by a condensation reaction between the carboxyl group of one amino acid and the amino group of another amino acid.

Question 3

When an unknown peptide containing five amino acids is treated with an enzyme that hydrolyzes only the serine-leucine peptide bond, the fragments Leu-Cys, Ser, Leu-Ser are formed. What was the original amino acid sequence in the peptide?

Accepted Answer

Since the enzyme only hydrolyzes the serine-leucine bond, the original peptide must have contained a serine-leucine bond that was cleaved to give the two fragments Leu-Ser and Ser. The remaining portion of the peptide must have contained a leucine-cysteine bond. The only option that fits this condition is D: Ser-Leu-Ser-Leu-Cys.

Question 4

Why might a change in pH cause a protein to denature?

Accepted Answer

A change in pH can cause the functional groups on a protein to become protonated or deprotonated. This can alter the charges on the protein, disrupting the electrostatic interactions that hold the protein's tertiary or quaternary structure together. This can cause the protein to denature or lose its functional shape. The other options are not directly related to changes in pH.

Question 5

Silk contains many pleated sheets, which consist predominately of amino acids such as phenylalanine and valine. Silk is more waterproof than cotton. Why?

Accepted Answer

The pleated sheet structure of silk occurs when mostly nonpolar amino acids are grouped together. Nonpolar molecules are hydrophobic, meaning they repel water. This property makes silk more waterproof than cotton, which has a different chemical structure.

Question 6

Which of the above pairs of side chains could be involved in a hydrophobic interaction?

Accepted Answer

The answer of Which of the above pairs of side...

Question 7

Why is a permanent wave not really permanent?

Accepted Answer

A permanent wave involves breaking and reforming disulfide bonds in the hair to create curls or waves. However, these bonds can only be broken and reformed a finite number of times before becoming too damaged. As new, untreated hair grows in to replace the treated old hair, it is not affected by the permanent wave chemicals and remains straight. Therefore, a permanent wave is not truly permanent as it only affects the hair that is initially treated.

Question 8

How do inhibitors work to prevent an enzyme from functioning?

Accepted Answer

Inhibitors can prevent enzyme function by blocking the receptor site, altering the receptor site, or binding to the enzyme, making all the options correct.

Question 9

Which of the above pairs of side chains could be involved in an ionic interaction?

Accepted Answer

The answer of Which of the above pairs of side...

Question 10

What is the cause of secondary structure in a protein?

Accepted Answer

Secondary structure in a protein is mainly caused by short range interactions between neighboring amino acids, such as hydrogen bonding between the carbonyl oxygen and amino hydrogen of different peptide bonds in the protein chain. These interactions lead to the formation of α-helices and β-sheets, which are the major components of protein secondary structure. Covalent bonding between different protein molecules (B) is not involved in the formation of secondary structure within a single protein molecule. Noncovalent interaction of groups of protein molecules (C) is more relevant to quaternary structure, which refers to the assembly of multiple protein subunits. Long distance conformation changes due to a large number of weak interactions (D) may lead to the formation of tertiary structure, but not secondary structure, which is primarily determined by local interactions.

Question 11

Which of the above pairs of side chains could be involved in a hydrogen bonding interaction?

Accepted Answer

The answer of Which of the above pairs of side...

Question 12

The following statement describes what level of structure in a protein? The set of linked amino acids folds repeatedly and creates a large linear globular shape.

Accepted Answer

The term "folds" implies that the amino acids are forming specific 3D structures, which is indicative of tertiary structure. A large linear globular shape suggests that this is the final, 3D organization of the protein. Therefore, the statement is describing the tertiary structure of a protein.

Question 13

The following statement describes what level of structure in a protein? The chain of amino acids coils into a helix.

Accepted Answer

The coiling of the chain of amino acids into a helix is a description of the secondary structure in a protein.

Question 14

You are a beautician about to apply a reducing agent to a customer with fine hair who wants to have his hair curly. Should the reducing agent be regular strength, concentrated, or diluted?

Accepted Answer

Fine hair is often fragile and thin, so it is important to be cautious when applying chemicals to it. Diluting the reducing agent will reduce the strength and limit the potential damage to the hair. A concentrated or regular strength reducing agent may be too harsh and cause the hair to break or fall out.

Question 15

The following statement describes what level of structure in a protein? The chain of amino acids layers into a large sheet.

Accepted Answer

The description given in the statement fits the definition of the secondary structure of a protein, where the amino acid chain is folded into a regular structure like an alpha helix or beta sheet.

Question 16

The following statement describes what level of structure in a protein? Several separate proteins link together to form an active enzyme.

Accepted Answer

Quaternary structure refers to the arrangement and bonding of multiple protein subunits to form a functional protein complex, such as an enzyme. Therefore, the statement describes quaternary structure.

Question 17

The following statement describes what level of structure in a protein? The sequence of amino acids is Asp-Asp-Arg-Asn-Met-Met- etc.

Accepted Answer

The sequence of amino acids refers to the primary structure of a protein.

Question 18

What is the purpose of an enzyme?

Accepted Answer

Enzymes are proteins that act as catalysts in biochemical reactions, which means they speed up the rate of the reaction without being consumed or altered themselves.

Question 19

Why can't your body produce proteins from carbohydrates and fats alone?

Accepted Answer

Proteins are made up of amino acids, which have an amine group that requires a nitrogen atom. Carbohydrates and fats do not contain nitrogen, so they cannot be used to create proteins.

Question 20

Proteins are ________ that have some biological function in living systems.

Accepted Answer

Proteins are made up of one or more chains of amino acids called polypeptides. Therefore, A is the correct choice as it defines the basic building blocks of proteins. B is incorrect as monomers refer to the individual units that make up a polymer, and proteins are not polymers. C is incorrect as starches are a different type of biomolecule. D is also incorrect as hormones are a specific type of protein with a regulatory function, but not all proteins are hormones. E is incorrect as one of the previous choices must be correct.

Quiz 13: Nutrients of Life

Which of the above pairs of side chains could be involved in a hydrophilic interaction?

What is the functional group that links amino acids together to form proteins?

When an unknown peptide containing five amino acids is treated with an enzyme that hydrolyzes only the serine-leucine peptide bond, the fragments Leu-Cys, Ser, Leu-Ser are formed. What was the original amino acid sequence in the peptide?

Why might a change in pH cause a protein to denature?

Silk contains many pleated sheets, which consist predominately of amino acids such as phenylalanine and valine. Silk is more waterproof than cotton. Why?

Which of the above pairs of side chains could be involved in a hydrophobic interaction?

Why is a permanent wave not really permanent?

How do inhibitors work to prevent an enzyme from functioning?

Which of the above pairs of side chains could be involved in an ionic interaction?

What is the cause of secondary structure in a protein?

Which of the above pairs of side chains could be involved in a hydrogen bonding interaction?

The following statement describes what level of structure in a protein? The set of linked amino acids folds repeatedly and creates a large linear globular shape.

The following statement describes what level of structure in a protein? The chain of amino acids coils into a helix.

You are a beautician about to apply a reducing agent to a customer with fine hair who wants to have his hair curly. Should the reducing agent be regular strength, concentrated, or diluted?

The following statement describes what level of structure in a protein? The chain of amino acids layers into a large sheet.

The following statement describes what level of structure in a protein? Several separate proteins link together to form an active enzyme.

The following statement describes what level of structure in a protein? The sequence of amino acids is Asp-Asp-Arg-Asn-Met-Met- etc.

What is the purpose of an enzyme?

Why can't your body produce proteins from carbohydrates and fats alone?

Proteins are ________ that have some biological function in living systems.