Question 1

Which of the following best explains why proteins can perform such a wide variety of functions in cells?

Accepted Answer

Proteins have diverse structures due to the variability of their amino acid side chains (R groups).

Question 2

Which of the following is a correct description of the structure of an amino acid at physiological pH?

Accepted Answer

The amino group is positively charged and the carboxyl group is negatively charged.

Question 3

A mutation changes a glutamic acid residue to a valine residue in the beta subunit of hemoglobin. Which of the following best describes the consequence of this change?

Accepted Answer

The protein becomes more hydrophobic at that position, leading to aggregation and sickle cell disease.

Question 4

Which type of bond is primarily responsible for stabilizing the secondary structure of proteins?

Accepted Answer

Hydrogen bonds between backbone atoms

Question 5

Which of the following best describes the directionality of polypeptide synthesis?

Accepted Answer

From the N terminus to the C terminus

Question 6

Which of the following interactions is unique to the tertiary structure of proteins and not found in secondary structure?

Accepted Answer

Disulfide bridges between cysteine side chains

Question 7

A protein is exposed to high heat and extreme pH, causing it to lose its three-dimensional structure but not its primary sequence. What is this process called?

Accepted Answer

Denaturation

Question 8

Which of the following amino acids would most likely be found in the interior of a protein embedded in a cell membrane?

Accepted Answer

Valine

Question 9

Which of the following best describes the quaternary structure of a protein?

Accepted Answer

The association of two or more polypeptide subunits into a functional protein

Question 10

Which experimental technique is commonly used to determine the three-dimensional structure of a protein at atomic resolution?

Accepted Answer

X-ray crystallography

Question 11

Which of the following statements about peptide bonds is correct?

Accepted Answer

Peptide bonds are covalent bonds formed between the amino group of one amino acid and the carboxyl group of another.

Question 12

Which of the following changes would most likely disrupt ionic bonds in a protein's tertiary structure?

Accepted Answer

A change in pH

Question 13

Which of the following best explains why sickle-cell hemoglobin forms fibers inside red blood cells?

Accepted Answer

A hydrophilic amino acid is replaced by a hydrophobic one, causing abnormal aggregation.

Question 14

Which of the following is NOT a function of proteins?

Accepted Answer

Storing genetic information

Question 15

Which of the following bonds or interactions is the strongest in stabilizing protein tertiary structure?

Accepted Answer

Disulfide bridges

Question 16

A protein is composed of two identical alpha subunits and two identical beta subunits. What is the best term to describe this protein's quaternary structure?

Accepted Answer

Tetramer

Question 17

Which of the following best describes the role of the R group in an amino acid?

Accepted Answer

It determines the specific properties and function of the amino acid.

Question 18

Which of the following scenarios would most likely result in a protein being denatured?

Accepted Answer

A protein is exposed to high heat and extreme pH.

Question 19

Which of the following is a real-life example of a protein's function being directly related to its structure?

Accepted Answer

The ability of hemoglobin to carry oxygen is lost when its structure is altered by a single amino acid mutation.

Bio 100 LEC Chapter 5 Part 2 UPDATED

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