WGU D312 Anatomy and Physiology I
OA Actual Exam 2025/2026 | Complete
Verified Questions & Detailed Answers
| 100% Guaranteed Pass
WGU D312 — Anatomy & Physiology I
OA Exam Preparation | 300 Multiple Choice Questions
Complete with CORRECT ANSWER & RATIONALE
Q1. What is the most abundant chemical compound found in the human body?
A. Glucose
B. Protein
C. Water
D. Lipids
E. DNA
CORRECT ANSWER: C. Water RATIONALE: Water makes up approximately
60–70% of the human body by weight, serving as the primary solvent for biochemical
reactions, a medium for transport, and a temperature regulator throughout the body.
Q2. An atom that has gained or lost electrons is called a:
A. Molecule
B. Isotope
C. Compound
D. Ion
E. Radical
CORRECT ANSWER: D. Ion RATIONALE: Ions are atoms or molecules that
have gained or lost one or more electrons, giving them a net positive (cation) or
negative (anion) charge. This is essential in nerve impulse transmission and muscle
contraction.
,Q3. Which type of bond holds water molecules together through hydrogen
bonding?
A. Ionic bond
B. Covalent bond
C. Peptide bond
D. Polar covalent bond
E. Hydrogen bond
CORRECT ANSWER: E. Hydrogen bond RATIONALE: Hydrogen bonds
form between the slightly positive hydrogen atom of one water molecule and the slightly
negative oxygen of another. These bonds give water its unique cohesive, adhesive, and
thermal properties.
Q4. What is the pH of a solution considered neutral?
A. 5
B. 6
C. 7
D. 8
E. 9
CORRECT ANSWER: C. 7 RATIONALE: A pH of 7 is neutral, meaning the
concentration of hydrogen ions (H⁺) equals the concentration of hydroxide ions (OH⁻).
Values below 7 are acidic; values above 7 are basic (alkaline).
Q5. Which macromolecule serves as the primary source of quick energy for the
human body?
A. Proteins
B. Nucleic acids
C. Lipids
D. Carbohydrates
, E. Steroids
CORRECT ANSWER: D. Carbohydrates RATIONALE: Carbohydrates,
especially glucose, are the body's preferred and most quickly metabolized source of
energy. They are broken down through glycolysis and cellular respiration to produce
ATP.
Q6. Which of the following best describes a catalyst in a biological system?
A. A molecule that stores genetic information
B. A molecule that speeds up a chemical reaction without being consumed
C. A molecule that carries oxygen in the blood
D. A molecule that builds cell membranes
E. A molecule that breaks down fats
CORRECT ANSWER: B. A molecule that speeds up a chemical reaction
without being consumed RATIONALE: Enzymes are biological catalysts —
proteins that lower the activation energy of chemical reactions and speed them up
without being permanently changed or consumed in the process.
Q7. The monomer unit of proteins is called a:
A. Nucleotide
B. Fatty acid
C. Monosaccharide
D. Amino acid
E. Glycerol
CORRECT ANSWER: D. Amino acid RATIONALE: Proteins are polymers
made up of amino acid monomers linked together by peptide bonds. There are 20
standard amino acids used in protein synthesis, and their sequence determines protein
structure and function.
Q8. Which of the following elements is NOT commonly found in organic
molecules?
, A. Carbon
B. Hydrogen
C. Oxygen
D. Nitrogen
E. Neon
CORRECT ANSWER: E. Neon RATIONALE: Neon is a noble (inert) gas that
does not form chemical bonds and is not found in organic molecules. Organic molecules
are primarily composed of carbon, hydrogen, oxygen, and nitrogen.
Q9. A solution with a pH of 3 compared to a solution with a pH of 5 is:
A. 2 times more acidic
B. 10 times more acidic
C. 100 times more acidic
D. 2 times more basic
E. The same acidity
CORRECT ANSWER: C. 100 times more acidic RATIONALE: The pH scale
is logarithmic. Each unit change in pH represents a 10-fold change in hydrogen ion
concentration. Therefore, a difference of 2 pH units means a 10² = 100-fold difference in
acidity.
Q10. Which of the following describes a decomposition reaction?
A. A + B → AB
B. AB → A + B
C. AB + CD → AC + BD
D. A + B → C + D
E. A → A + A
CORRECT ANSWER: B. AB → A + B RATIONALE: A decomposition reaction
involves a single compound breaking down into two or more simpler substances.
OA Actual Exam 2025/2026 | Complete
Verified Questions & Detailed Answers
| 100% Guaranteed Pass
WGU D312 — Anatomy & Physiology I
OA Exam Preparation | 300 Multiple Choice Questions
Complete with CORRECT ANSWER & RATIONALE
Q1. What is the most abundant chemical compound found in the human body?
A. Glucose
B. Protein
C. Water
D. Lipids
E. DNA
CORRECT ANSWER: C. Water RATIONALE: Water makes up approximately
60–70% of the human body by weight, serving as the primary solvent for biochemical
reactions, a medium for transport, and a temperature regulator throughout the body.
Q2. An atom that has gained or lost electrons is called a:
A. Molecule
B. Isotope
C. Compound
D. Ion
E. Radical
CORRECT ANSWER: D. Ion RATIONALE: Ions are atoms or molecules that
have gained or lost one or more electrons, giving them a net positive (cation) or
negative (anion) charge. This is essential in nerve impulse transmission and muscle
contraction.
,Q3. Which type of bond holds water molecules together through hydrogen
bonding?
A. Ionic bond
B. Covalent bond
C. Peptide bond
D. Polar covalent bond
E. Hydrogen bond
CORRECT ANSWER: E. Hydrogen bond RATIONALE: Hydrogen bonds
form between the slightly positive hydrogen atom of one water molecule and the slightly
negative oxygen of another. These bonds give water its unique cohesive, adhesive, and
thermal properties.
Q4. What is the pH of a solution considered neutral?
A. 5
B. 6
C. 7
D. 8
E. 9
CORRECT ANSWER: C. 7 RATIONALE: A pH of 7 is neutral, meaning the
concentration of hydrogen ions (H⁺) equals the concentration of hydroxide ions (OH⁻).
Values below 7 are acidic; values above 7 are basic (alkaline).
Q5. Which macromolecule serves as the primary source of quick energy for the
human body?
A. Proteins
B. Nucleic acids
C. Lipids
D. Carbohydrates
, E. Steroids
CORRECT ANSWER: D. Carbohydrates RATIONALE: Carbohydrates,
especially glucose, are the body's preferred and most quickly metabolized source of
energy. They are broken down through glycolysis and cellular respiration to produce
ATP.
Q6. Which of the following best describes a catalyst in a biological system?
A. A molecule that stores genetic information
B. A molecule that speeds up a chemical reaction without being consumed
C. A molecule that carries oxygen in the blood
D. A molecule that builds cell membranes
E. A molecule that breaks down fats
CORRECT ANSWER: B. A molecule that speeds up a chemical reaction
without being consumed RATIONALE: Enzymes are biological catalysts —
proteins that lower the activation energy of chemical reactions and speed them up
without being permanently changed or consumed in the process.
Q7. The monomer unit of proteins is called a:
A. Nucleotide
B. Fatty acid
C. Monosaccharide
D. Amino acid
E. Glycerol
CORRECT ANSWER: D. Amino acid RATIONALE: Proteins are polymers
made up of amino acid monomers linked together by peptide bonds. There are 20
standard amino acids used in protein synthesis, and their sequence determines protein
structure and function.
Q8. Which of the following elements is NOT commonly found in organic
molecules?
, A. Carbon
B. Hydrogen
C. Oxygen
D. Nitrogen
E. Neon
CORRECT ANSWER: E. Neon RATIONALE: Neon is a noble (inert) gas that
does not form chemical bonds and is not found in organic molecules. Organic molecules
are primarily composed of carbon, hydrogen, oxygen, and nitrogen.
Q9. A solution with a pH of 3 compared to a solution with a pH of 5 is:
A. 2 times more acidic
B. 10 times more acidic
C. 100 times more acidic
D. 2 times more basic
E. The same acidity
CORRECT ANSWER: C. 100 times more acidic RATIONALE: The pH scale
is logarithmic. Each unit change in pH represents a 10-fold change in hydrogen ion
concentration. Therefore, a difference of 2 pH units means a 10² = 100-fold difference in
acidity.
Q10. Which of the following describes a decomposition reaction?
A. A + B → AB
B. AB → A + B
C. AB + CD → AC + BD
D. A + B → C + D
E. A → A + A
CORRECT ANSWER: B. AB → A + B RATIONALE: A decomposition reaction
involves a single compound breaking down into two or more simpler substances.
