P R E - A S S E S S M E N T E X A M I N AT I ON R E V I E W
WGU C190
Introduction
to Biology
Comprehensive 55-question practice examination
aligned with WGU C190 course competencies and the
latest 2026/2027 Pre-Assessment V1 format. Covers
chemistry of life, cell structure, metabolism, genetics,
molecular biology, and evolution with verified answers
and detailed
Format: scientific
Multiple rationales.
Choice (A-D) | Questions: 55 | Sections: 6
Update: Latest 2026/2027 | Answers: 100% Verified
S C I E N C E E D U C AT I O N · W G U C 1 9 0 E X A M P R E PA R AT I O N
,WGU C190 Introduction to Biology | Pre-Assessment Exam Review | 2026/2027
Section 1: Chemistry of Life and Biological Molecules
Q1: A researcher analyzes a molecule and determines it contains carbon, hydrogen, and oxygen in a 1:2:1
ratio. The molecule is a primary source of quick energy for cells and is classified as a monosaccharide. Which
of the following best describes this molecule?
A. A triglyceride composed of glycerol and three fatty acid chains
B. A hexose sugar such as glucose with the formula C6H12O6 [CORRECT]
C. A nucleotide consisting of a phosphate group, pentose sugar, and nitrogenous base
D. An amino acid containing an amino group, carboxyl group, and variable R group
Correct Answer: B
Rationale: Carbohydrates have the general empirical formula (CH2O)n, reflecting a 1:2:1 ratio of carbon, hydrogen,
and oxygen. Glucose is a hexose monosaccharide (C6H12O6) and serves as the primary quick-energy source for cells
through glycolysis and cellular respiration. Triglycerides are lipids, nucleotides are the building blocks of nucleic acids,
and amino acids are the monomers of proteins, none of which share this specific elemental ratio.
Q2: Water exhibits a high specific heat capacity, which allows it to moderate temperature changes in
organisms and environments. Which property of water molecules is directly responsible for this characteristic?
A. The ability of water molecules to form covalent bonds with each other
B. Hydrogen bonding between water molecules that requires substantial energy to break
[CORRECT]
C. The nonpolar nature of water molecules that prevents temperature absorption
D. The low heat of vaporization that allows water to cool surfaces rapidly
Correct Answer: B
Rationale: Water's high specific heat results from extensive hydrogen bonding between molecules. Before water
temperature can increase, energy must first disrupt these hydrogen bonds. This property is biologically critical because
it helps organisms maintain stable internal temperatures and allows large bodies of water to moderate climate.
Covalent bonds form within water molecules (H-O), not between them, and water is polar, not nonpolar. Water
actually has a high, not low, heat of vaporization.
Q3: A biology student adds a small amount of sodium hydroxide (NaOH) to a buffered solution and observes
that the pH changes by only 0.02 units. Which of the following best explains this result?
A. NaOH is a weak base and therefore has minimal effect on pH
B. The buffer system accepts hydrogen ions from NaOH, neutralizing its effect
C. The buffer system donates hydrogen ions to neutralize the added hydroxide ions [CORRECT]
D. The solution already had such a high pH that additional base has negligible impact
Correct Answer: C
Rationale: Buffers resist pH changes by weak acid/base conjugate pairs. When a base (NaOH, which dissociates into
Na+ and OH-) is added, the weak acid component of the buffer donates H+ ions to neutralize the OH- ions, forming
water. This minimizes the pH shift. NaOH is actually a strong base, not weak. Buffers work by either donating H+
(when base is added) or accepting H+ (when acid is added), not by accepting H+ from base. The explanation does not
depend on the initial pH being extremely high.
Q4: Which of the following correctly pairs a biological macromolecule with its monomer subunit and a
primary function in living organisms?
100% Correct Verified Answers Page 1
, WGU C190 Introduction to Biology | Pre-Assessment Exam Review | 2026/2027
A. Protein - amino acids - long-term energy storage
B. Nucleic acid - nucleotides - primary component of cell membranes
C. Carbohydrate - monosaccharides - immediate energy source and structural support
[CORRECT]
D. Lipid - fatty acids - catalyzing biochemical reactions
Correct Answer: C
Rationale: Carbohydrates are composed of monosaccharide monomers and serve as immediate energy sources (e.g.,
glucose in glycolysis) and structural components (e.g., cellulose in plant cell walls). Proteins are made of amino acids
but function as enzymes, transport molecules, and structural components rather than long-term energy storage (that role
belongs to lipids). Nucleic acids are made of nucleotides but store genetic information, not membrane structure
(phospholipids do). Lipids are not polymers of fatty acids in the traditional sense and do not catalyze reactions
(enzymes, which are proteins, do).
Q5: A scientist is studying a protein that has folded into a three-dimensional globular shape due to interactions
between R groups of amino acids, including disulfide bridges and hydrophobic interactions. Which level of
protein structure is being described?
A. Primary structure, which is the linear sequence of amino acids
B. Secondary structure, which involves alpha helices and beta pleated sheets
C. Tertiary structure, which is the overall three-dimensional shape of a single polypeptide
[CORRECT]
D. Quaternary structure, which involves the arrangement of multiple polypeptide subunits
Correct Answer: C
Rationale: Tertiary structure refers to the complete 3D conformation of a single polypeptide chain, stabilized by
interactions between R groups including hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals forces,
and disulfide bridges (covalent bonds between cysteine residues). Primary structure is the linear amino acid sequence
only. Secondary structure involves local folding patterns (alpha helices, beta sheets) stabilized by hydrogen bonds along
the backbone. Quaternary structure involves the assembly of multiple polypeptide subunits.
Q6: In a DNA molecule, a researcher identifies that adenine constitutes 22% of the nitrogenous bases.
According to Chargaff's rules of complementary base pairing, what percentage of the bases would be cytosine?
A. 22%
B. 28% [CORRECT]
C. 44%
D. 56%
Correct Answer: B
Rationale: Chargaff's rules state that in DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine
(C). If A = 22%, then T = 22% as well, accounting for 44% of bases total. The remaining 56% must be split equally
between G and C (since G pairs with C), giving C = 28%. This complementary pairing (A=T, G=C) is fundamental to
DNA's double-helix structure and ensures accurate replication.
Q7: An enzyme catalyzes the conversion of substrate S into product P. When a molecule that closely
resembles the substrate is added to the reaction, it competes for the enzyme's active site but is not converted
into product. Which type of inhibition is occurring, and what is its effect on the reaction kinetics?
A. Non-competitive inhibition; Vmax decreases and Km remains unchanged
B. Competitive inhibition; Vmax remains unchanged but apparent Km increases [CORRECT]
100% Correct Verified Answers Page 2
WGU C190
Introduction
to Biology
Comprehensive 55-question practice examination
aligned with WGU C190 course competencies and the
latest 2026/2027 Pre-Assessment V1 format. Covers
chemistry of life, cell structure, metabolism, genetics,
molecular biology, and evolution with verified answers
and detailed
Format: scientific
Multiple rationales.
Choice (A-D) | Questions: 55 | Sections: 6
Update: Latest 2026/2027 | Answers: 100% Verified
S C I E N C E E D U C AT I O N · W G U C 1 9 0 E X A M P R E PA R AT I O N
,WGU C190 Introduction to Biology | Pre-Assessment Exam Review | 2026/2027
Section 1: Chemistry of Life and Biological Molecules
Q1: A researcher analyzes a molecule and determines it contains carbon, hydrogen, and oxygen in a 1:2:1
ratio. The molecule is a primary source of quick energy for cells and is classified as a monosaccharide. Which
of the following best describes this molecule?
A. A triglyceride composed of glycerol and three fatty acid chains
B. A hexose sugar such as glucose with the formula C6H12O6 [CORRECT]
C. A nucleotide consisting of a phosphate group, pentose sugar, and nitrogenous base
D. An amino acid containing an amino group, carboxyl group, and variable R group
Correct Answer: B
Rationale: Carbohydrates have the general empirical formula (CH2O)n, reflecting a 1:2:1 ratio of carbon, hydrogen,
and oxygen. Glucose is a hexose monosaccharide (C6H12O6) and serves as the primary quick-energy source for cells
through glycolysis and cellular respiration. Triglycerides are lipids, nucleotides are the building blocks of nucleic acids,
and amino acids are the monomers of proteins, none of which share this specific elemental ratio.
Q2: Water exhibits a high specific heat capacity, which allows it to moderate temperature changes in
organisms and environments. Which property of water molecules is directly responsible for this characteristic?
A. The ability of water molecules to form covalent bonds with each other
B. Hydrogen bonding between water molecules that requires substantial energy to break
[CORRECT]
C. The nonpolar nature of water molecules that prevents temperature absorption
D. The low heat of vaporization that allows water to cool surfaces rapidly
Correct Answer: B
Rationale: Water's high specific heat results from extensive hydrogen bonding between molecules. Before water
temperature can increase, energy must first disrupt these hydrogen bonds. This property is biologically critical because
it helps organisms maintain stable internal temperatures and allows large bodies of water to moderate climate.
Covalent bonds form within water molecules (H-O), not between them, and water is polar, not nonpolar. Water
actually has a high, not low, heat of vaporization.
Q3: A biology student adds a small amount of sodium hydroxide (NaOH) to a buffered solution and observes
that the pH changes by only 0.02 units. Which of the following best explains this result?
A. NaOH is a weak base and therefore has minimal effect on pH
B. The buffer system accepts hydrogen ions from NaOH, neutralizing its effect
C. The buffer system donates hydrogen ions to neutralize the added hydroxide ions [CORRECT]
D. The solution already had such a high pH that additional base has negligible impact
Correct Answer: C
Rationale: Buffers resist pH changes by weak acid/base conjugate pairs. When a base (NaOH, which dissociates into
Na+ and OH-) is added, the weak acid component of the buffer donates H+ ions to neutralize the OH- ions, forming
water. This minimizes the pH shift. NaOH is actually a strong base, not weak. Buffers work by either donating H+
(when base is added) or accepting H+ (when acid is added), not by accepting H+ from base. The explanation does not
depend on the initial pH being extremely high.
Q4: Which of the following correctly pairs a biological macromolecule with its monomer subunit and a
primary function in living organisms?
100% Correct Verified Answers Page 1
, WGU C190 Introduction to Biology | Pre-Assessment Exam Review | 2026/2027
A. Protein - amino acids - long-term energy storage
B. Nucleic acid - nucleotides - primary component of cell membranes
C. Carbohydrate - monosaccharides - immediate energy source and structural support
[CORRECT]
D. Lipid - fatty acids - catalyzing biochemical reactions
Correct Answer: C
Rationale: Carbohydrates are composed of monosaccharide monomers and serve as immediate energy sources (e.g.,
glucose in glycolysis) and structural components (e.g., cellulose in plant cell walls). Proteins are made of amino acids
but function as enzymes, transport molecules, and structural components rather than long-term energy storage (that role
belongs to lipids). Nucleic acids are made of nucleotides but store genetic information, not membrane structure
(phospholipids do). Lipids are not polymers of fatty acids in the traditional sense and do not catalyze reactions
(enzymes, which are proteins, do).
Q5: A scientist is studying a protein that has folded into a three-dimensional globular shape due to interactions
between R groups of amino acids, including disulfide bridges and hydrophobic interactions. Which level of
protein structure is being described?
A. Primary structure, which is the linear sequence of amino acids
B. Secondary structure, which involves alpha helices and beta pleated sheets
C. Tertiary structure, which is the overall three-dimensional shape of a single polypeptide
[CORRECT]
D. Quaternary structure, which involves the arrangement of multiple polypeptide subunits
Correct Answer: C
Rationale: Tertiary structure refers to the complete 3D conformation of a single polypeptide chain, stabilized by
interactions between R groups including hydrogen bonds, ionic bonds, hydrophobic interactions, van der Waals forces,
and disulfide bridges (covalent bonds between cysteine residues). Primary structure is the linear amino acid sequence
only. Secondary structure involves local folding patterns (alpha helices, beta sheets) stabilized by hydrogen bonds along
the backbone. Quaternary structure involves the assembly of multiple polypeptide subunits.
Q6: In a DNA molecule, a researcher identifies that adenine constitutes 22% of the nitrogenous bases.
According to Chargaff's rules of complementary base pairing, what percentage of the bases would be cytosine?
A. 22%
B. 28% [CORRECT]
C. 44%
D. 56%
Correct Answer: B
Rationale: Chargaff's rules state that in DNA, adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine
(C). If A = 22%, then T = 22% as well, accounting for 44% of bases total. The remaining 56% must be split equally
between G and C (since G pairs with C), giving C = 28%. This complementary pairing (A=T, G=C) is fundamental to
DNA's double-helix structure and ensures accurate replication.
Q7: An enzyme catalyzes the conversion of substrate S into product P. When a molecule that closely
resembles the substrate is added to the reaction, it competes for the enzyme's active site but is not converted
into product. Which type of inhibition is occurring, and what is its effect on the reaction kinetics?
A. Non-competitive inhibition; Vmax decreases and Km remains unchanged
B. Competitive inhibition; Vmax remains unchanged but apparent Km increases [CORRECT]
100% Correct Verified Answers Page 2
