Chapter 3 Review

Which of the following best describes the structure of an amino acid?

• A central carbon atom bonded to a hydrogen atom, an amino group, a carboxyl group, and a variable R group

• A central nitrogen atom bonded to two hydrogen atoms and a carboxyl group

• A central carbon atom bonded to four identical groups

• A central oxygen atom bonded to a hydrogen atom, an amino group, and a carboxyl group

In water, what do the amino and carboxyl groups of amino acids ionize to?

• NH₃⁺ and COO⁻

• NH₂ and COOH

• NH₄⁺ and CO₂

• NH₃ and COOH⁻

Refer to the diagram below. Which part of the amino acid structure is ionized to NH₃⁺ in water?

• Amino group

• Carboxyl group

• Side chain

• Hydrogen atom

How many major amino acids are found in organisms, categorized based on their side chains?

• 10

• 15

• 20

• 25

Why do the properties of amino acids vary?

• Because all amino acids have the same R-group

• Because R-groups vary among amino acids

• Because amino acids have different peptide bonds

• Because amino acids are not found in organisms

Which amino acid is classified as having a nonpolar side chain?

• Glycine (Gly)

• Glutamine (Gln)

• Arginine (Arg)

• Serine (Ser)

Tags

NGSS.HS-LS1-6

What is the term used to describe R-groups that interact with water?

• Hydrophobic

• Hydrophilic

• Nonpolar

• Neutral

Which type of R-group does NOT form hydrogen bonds with water?

• Polar R-groups

• Charged R-groups

• Nonpolar R-groups

• Acidic R-groups

If a protein has a primary structure length ranging from two amino acid residues to tens of thousands, what does this indicate about protein diversity?

• Proteins are always short molecules.

• Protein diversity is limited by length.

• Proteins can vary greatly in length, contributing to their diversity.

• All proteins have the same length.

Which level of protein structure is considered fundamental to the higher levels of protein structure?

• Primary structure

• Secondary structure

• Tertiary structure

• Quaternary structure