Question 1

Which of the following is the monomer (subunit) of proteins?

Accepted Answer

Amino acid

Question 2

Which elements are always present in the structure of an amino acid?

Accepted Answer

Carbon, hydrogen, oxygen, nitrogen

Question 3

A peptide bond forms between which two functional groups of adjacent amino acids?

Accepted Answer

Amino group and carboxyl group

Question 4

Which formula best represents the general structure of an amino acid?

Accepted Answer

$$\mathrm{R{-}CH(NH_2$){-}COOH}$$

Question 5

What distinguishes each of the 20 different amino acids from one another?

Accepted Answer

The type of side chain (R group) attached to the central carbon

Question 6

If an amino acid has a nonpolar side chain, where is it most likely to be found in a protein's 3D structure?

Accepted Answer

Buried in the interior of the protein, away from water

Question 7

Which level of protein structure is defined by the sequence of amino acids?

Accepted Answer

Primary structure

Question 8

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

Accepted Answer

Hydrogen bonds

Question 9

Hemoglobin is an example of a protein with which level of structure?

Accepted Answer

Quaternary structure

Question 10

Which of the following is NOT a major function of proteins in living organisms?

Accepted Answer

Energy storage

Question 11

A mutation changes a polar amino acid to a nonpolar one in the surface region of a protein. What is the most likely effect?

Accepted Answer

The protein may lose solubility in water and misfold

Question 12

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

Accepted Answer

The overall 3D shape formed by interactions among side chains (R groups)

Question 13

Which functional group is present in all amino acids and is responsible for their acidic properties?

Accepted Answer

Carboxyl group ($$\mathrm{-COOH})$$

Question 14

Which of the following scenarios best illustrates the role of proteins as enzymes?

Accepted Answer

Lactase catalyzing the hydrolysis of lactose into glucose and galactose

Question 15

Which of the following statements about peptide bonds is correct?

Accepted Answer

They are covalent bonds formed by dehydration synthesis between amino acids

Question 16

A protein loses its quaternary structure but retains its tertiary structure. Which of the following is most likely to occur?

Accepted Answer

The protein will lose its ability to function as a multi-subunit complex

Question 17

Which of the following amino acids is most likely to be found on the exterior of a protein in an aqueous environment?

Accepted Answer

Serine (polar side chain)

Question 18

Which process is responsible for the formation of a peptide bond between two amino acids?

Accepted Answer

Dehydration synthesis (condensation reaction)

Question 19

Which of the following best explains why sickle cell anemia is caused by a single amino acid substitution in hemoglobin?

Accepted Answer

A nonpolar amino acid replaces a polar one, altering the protein's shape and function

Question 20

Which of the following is a real-world example of a protein acting as a transport molecule?

Accepted Answer

Hemoglobin carrying oxygen in red blood cells

Proteins: Structure, Properties, and Functions (Concept 5.4)

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