03121 B MODERN BIOLOGY Monday, May 4, 2026 08:30am - 11:30am In Person
CUC McConomy WISNIEWSKI BRETT (bwisniew), WONG-NOONAN STEPHANIE
(sawong) Carnegie mellon university
Chapter 1: The Chemical Basis of Life (Questions 1–20)
1. Which element is found in all organic molecules?
A) Nitrogen
B) Oxygen
C) Carbon
D) Hydrogen
Answer: C
Rationale: Carbon is the fundamental element in organic chemistry because it can
form four stable covalent bonds and long chains. It is present in carbohydrates,
lipids, proteins, and nucleic acids.
2. The four most abundant elements in the human body are:
A) Carbon, hydrogen, oxygen, iron
B) Carbon, hydrogen, oxygen, nitrogen
,C) Carbon, oxygen, calcium, phosphorus
D) Oxygen, carbon, hydrogen, calcium
Answer: B
Rationale: By mass, the human body is approximately 65% oxygen, 18% carbon,
10% hydrogen, and 3% nitrogen. These four elements make up about 96% of the
body's weight.
3. Which type of bond is formed by the sharing of electrons between atoms?
A) Ionic bond
B) Hydrogen bond
C) Covalent bond
D) Peptide bond
Answer: C
Rationale: A covalent bond involves the sharing of one or more pairs of electrons.
Ionic bonds involve transfer of electrons, and hydrogen bonds are weak
attractions between a hydrogen atom and an electronegative atom.
4. Water's ability to moderate temperature is primarily due to:
,A) Its low specific heat
B) Its high specific heat and hydrogen bonding
C) Its ability to dissolve non‑polar substances
D) Its low heat of vaporization
Answer: B
Rationale: Water has a high specific heat because hydrogen bonds must be
broken for the temperature to rise. This property allows water to absorb or
release large amounts of heat with little temperature change, stabilizing body
temperature and aquatic environments.
5. A pH of 3 is:
A) Neutral
B) Weakly alkaline
C) Strongly acidic
D) Strongly alkaline
Answer: C
Rationale: pH is a logarithmic scale (0–14); values below 7 are acidic, above 7 are
basic. A pH of 3 is 10,000 times more acidic than a neutral pH of 7.
, 6. The four major classes of organic macromolecules are:
A) Carbohydrates, lipids, proteins, nucleic acids
B) Sugars, starches, fats, vitamins
C) Amino acids, nucleotides, monosaccharides, fatty acids
D) Carbohydrates, proteins, enzymes, hormones
Answer: A
Rationale: These four classes are the building blocks of cells. Carbohydrates
provide energy, lipids store energy and form membranes, proteins catalyze
reactions and provide structure, and nucleic acids store genetic information.
7. Which carbohydrate is the main storage form in animals?
A) Starch
B) Cellulose
C) Glycogen
D) Sucrose
Answer: C
CUC McConomy WISNIEWSKI BRETT (bwisniew), WONG-NOONAN STEPHANIE
(sawong) Carnegie mellon university
Chapter 1: The Chemical Basis of Life (Questions 1–20)
1. Which element is found in all organic molecules?
A) Nitrogen
B) Oxygen
C) Carbon
D) Hydrogen
Answer: C
Rationale: Carbon is the fundamental element in organic chemistry because it can
form four stable covalent bonds and long chains. It is present in carbohydrates,
lipids, proteins, and nucleic acids.
2. The four most abundant elements in the human body are:
A) Carbon, hydrogen, oxygen, iron
B) Carbon, hydrogen, oxygen, nitrogen
,C) Carbon, oxygen, calcium, phosphorus
D) Oxygen, carbon, hydrogen, calcium
Answer: B
Rationale: By mass, the human body is approximately 65% oxygen, 18% carbon,
10% hydrogen, and 3% nitrogen. These four elements make up about 96% of the
body's weight.
3. Which type of bond is formed by the sharing of electrons between atoms?
A) Ionic bond
B) Hydrogen bond
C) Covalent bond
D) Peptide bond
Answer: C
Rationale: A covalent bond involves the sharing of one or more pairs of electrons.
Ionic bonds involve transfer of electrons, and hydrogen bonds are weak
attractions between a hydrogen atom and an electronegative atom.
4. Water's ability to moderate temperature is primarily due to:
,A) Its low specific heat
B) Its high specific heat and hydrogen bonding
C) Its ability to dissolve non‑polar substances
D) Its low heat of vaporization
Answer: B
Rationale: Water has a high specific heat because hydrogen bonds must be
broken for the temperature to rise. This property allows water to absorb or
release large amounts of heat with little temperature change, stabilizing body
temperature and aquatic environments.
5. A pH of 3 is:
A) Neutral
B) Weakly alkaline
C) Strongly acidic
D) Strongly alkaline
Answer: C
Rationale: pH is a logarithmic scale (0–14); values below 7 are acidic, above 7 are
basic. A pH of 3 is 10,000 times more acidic than a neutral pH of 7.
, 6. The four major classes of organic macromolecules are:
A) Carbohydrates, lipids, proteins, nucleic acids
B) Sugars, starches, fats, vitamins
C) Amino acids, nucleotides, monosaccharides, fatty acids
D) Carbohydrates, proteins, enzymes, hormones
Answer: A
Rationale: These four classes are the building blocks of cells. Carbohydrates
provide energy, lipids store energy and form membranes, proteins catalyze
reactions and provide structure, and nucleic acids store genetic information.
7. Which carbohydrate is the main storage form in animals?
A) Starch
B) Cellulose
C) Glycogen
D) Sucrose
Answer: C
