,CHEM 210 Exam 3 | Biochemistry Exam Q&A
| Portage Learning
1. Which statement best defines an amino acid?
A) A carbohydrate containing a phosphate group
B) An organic molecule containing an amino group and a carboxyl group
C) A lipid composed exclusively of fatty acids
D) A nucleotide containing a nitrogenous base
Correct Answer: An organic molecule containing an amino group and a carboxyl
group
Rationale: Amino acids are the fundamental building blocks of proteins. A typical
amino acid contains an amino group, a carboxyl group, a hydrogen atom, and a variable
side chain attached to a central alpha-carbon. Carbohydrates, lipids, and nucleotides
have different defining structures.
2. What determines the unique chemical properties of an amino acid?
A) Its peptide bond
B) Its alpha-carboxyl group
C) Its R group or side chain
D) Its amino group
Correct Answer: Its R group or side chain
,Rationale: The R group varies among the standard amino acids and determines
properties such as polarity, charge, hydrophobicity, and reactivity. The amino and
carboxyl groups are common structural features, whereas the side chain provides much
of the chemical diversity found in proteins.
3. Which element distinguishes amino acids from many simple carbohydrates?
A) Carbon
B) Hydrogen
C) Oxygen
D) Nitrogen
Correct Answer: Nitrogen
Rationale: Amino acids contain nitrogen because of their amino groups. Carbon,
hydrogen, and oxygen are also present in many carbohydrates, so nitrogen is
particularly useful for distinguishing amino acids from simple carbohydrate structures.
4. How many standard amino acids are commonly incorporated into proteins through
the genetic code?
A) 10
B) 15
C) 20
D) 25
Correct Answer: 20
, Rationale: The standard genetic code specifies 20 common proteinogenic amino
acids. These amino acids can be arranged in many different sequences to produce
proteins with diverse structures and functions.
5. Which amino acid is classified as nonpolar and aliphatic?
A) Serine
B) Valine
C) Lysine
D) Aspartate
Correct Answer: Valine
Rationale: Valine has a branched aliphatic side chain that is nonpolar and
hydrophobic. Serine is polar but uncharged, lysine is positively charged, and aspartate is
negatively charged.
6. Which amino acid contains a hydroxyl group in its side chain?
A) Alanine
B) Threonine
C) Phenylalanine
D) Methionine
Correct Answer: Threonine
| Portage Learning
1. Which statement best defines an amino acid?
A) A carbohydrate containing a phosphate group
B) An organic molecule containing an amino group and a carboxyl group
C) A lipid composed exclusively of fatty acids
D) A nucleotide containing a nitrogenous base
Correct Answer: An organic molecule containing an amino group and a carboxyl
group
Rationale: Amino acids are the fundamental building blocks of proteins. A typical
amino acid contains an amino group, a carboxyl group, a hydrogen atom, and a variable
side chain attached to a central alpha-carbon. Carbohydrates, lipids, and nucleotides
have different defining structures.
2. What determines the unique chemical properties of an amino acid?
A) Its peptide bond
B) Its alpha-carboxyl group
C) Its R group or side chain
D) Its amino group
Correct Answer: Its R group or side chain
,Rationale: The R group varies among the standard amino acids and determines
properties such as polarity, charge, hydrophobicity, and reactivity. The amino and
carboxyl groups are common structural features, whereas the side chain provides much
of the chemical diversity found in proteins.
3. Which element distinguishes amino acids from many simple carbohydrates?
A) Carbon
B) Hydrogen
C) Oxygen
D) Nitrogen
Correct Answer: Nitrogen
Rationale: Amino acids contain nitrogen because of their amino groups. Carbon,
hydrogen, and oxygen are also present in many carbohydrates, so nitrogen is
particularly useful for distinguishing amino acids from simple carbohydrate structures.
4. How many standard amino acids are commonly incorporated into proteins through
the genetic code?
A) 10
B) 15
C) 20
D) 25
Correct Answer: 20
, Rationale: The standard genetic code specifies 20 common proteinogenic amino
acids. These amino acids can be arranged in many different sequences to produce
proteins with diverse structures and functions.
5. Which amino acid is classified as nonpolar and aliphatic?
A) Serine
B) Valine
C) Lysine
D) Aspartate
Correct Answer: Valine
Rationale: Valine has a branched aliphatic side chain that is nonpolar and
hydrophobic. Serine is polar but uncharged, lysine is positively charged, and aspartate is
negatively charged.
6. Which amino acid contains a hydroxyl group in its side chain?
A) Alanine
B) Threonine
C) Phenylalanine
D) Methionine
Correct Answer: Threonine
