C190 INTRO TO BIOLOGY OA — 250
PRACTICE EXAM QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALES
Chemistry of Life & Biological Molecules (Questions 1–35)
1. Which of the following is the smallest unit of matter that retains the
properties of an element?
A) Molecule
B) Atom
C) Cell
D) Proton
Correct Answer: B
Rationale: An atom is the smallest unit of matter that retains the properties of
an element. Molecules are combinations of atoms, cells are the basic unit of
life, and protons are subatomic particles that do not retain elemental
properties on their own.
2. What type of bond is formed when electrons are shared between atoms?
,A) Ionic bond
B) Hydrogen bond
C) Covalent bond
D) Van der Waals interaction
Correct Answer: C
Rationale: Covalent bonds involve the sharing of electron pairs between
atoms. Ionic bonds involve electron transfer, hydrogen bonds are weak
attractions between polar molecules, and Van der Waals interactions are weak
temporary attractions.
3. Which of the following macromolecules is primarily responsible for storing
genetic information?
A) Proteins
B) Carbohydrates
C) Lipids
D) Nucleic acids
Correct Answer: D
Rationale: Nucleic acids (DNA and RNA) store and transmit genetic
information. Proteins perform most cellular functions, carbohydrates provide
energy, and lipids store energy and form membranes.
,4. What are the four main categories of molecules known as "the molecules of
life"?
A) Water, salts, acids, bases
B) Lipids, carbohydrates, proteins, nucleic acids
C) Sugars, fats, vitamins, minerals
D) Amino acids, nucleotides, monosaccharides, fatty acids
Correct Answer: B
Rationale: The four main categories of biological macromolecules are lipids,
carbohydrates, proteins, and nucleic acids. These are essential for all living
organisms.
5. Which subatomic particle has a positive charge and is located in the
nucleus?
A) Electron
B) Neutron
C) Proton
D) Positron
Correct Answer: C
Rationale: Protons are positively charged particles found in the nucleus of an
atom. Electrons are negatively charged and orbit the nucleus, while neutrons
have no charge.
, 6. What is the primary function of carbohydrates in living organisms?
A) Genetic information storage
B) Energy storage and structural support
C) Catalyzing chemical reactions
D) Forming cell membranes
Correct Answer: B
Rationale: Carbohydrates primarily serve as energy sources (glucose) and
structural components (cellulose, chitin). They are not the primary genetic
material, catalysts, or membrane formers.
7. Which type of lipid is the main component of cell membranes?
A) Triglycerides
B) Steroids
C) Phospholipids
D) Waxes
Correct Answer: C
Rationale: Phospholipids are the primary structural component of cell
membranes, forming a bilayer. Triglycerides store energy, steroids include
hormones, and waxes provide waterproofing.
PRACTICE EXAM QUESTIONS AND CORRECT
ANSWERS WITH DETAILED RATIONALES
Chemistry of Life & Biological Molecules (Questions 1–35)
1. Which of the following is the smallest unit of matter that retains the
properties of an element?
A) Molecule
B) Atom
C) Cell
D) Proton
Correct Answer: B
Rationale: An atom is the smallest unit of matter that retains the properties of
an element. Molecules are combinations of atoms, cells are the basic unit of
life, and protons are subatomic particles that do not retain elemental
properties on their own.
2. What type of bond is formed when electrons are shared between atoms?
,A) Ionic bond
B) Hydrogen bond
C) Covalent bond
D) Van der Waals interaction
Correct Answer: C
Rationale: Covalent bonds involve the sharing of electron pairs between
atoms. Ionic bonds involve electron transfer, hydrogen bonds are weak
attractions between polar molecules, and Van der Waals interactions are weak
temporary attractions.
3. Which of the following macromolecules is primarily responsible for storing
genetic information?
A) Proteins
B) Carbohydrates
C) Lipids
D) Nucleic acids
Correct Answer: D
Rationale: Nucleic acids (DNA and RNA) store and transmit genetic
information. Proteins perform most cellular functions, carbohydrates provide
energy, and lipids store energy and form membranes.
,4. What are the four main categories of molecules known as "the molecules of
life"?
A) Water, salts, acids, bases
B) Lipids, carbohydrates, proteins, nucleic acids
C) Sugars, fats, vitamins, minerals
D) Amino acids, nucleotides, monosaccharides, fatty acids
Correct Answer: B
Rationale: The four main categories of biological macromolecules are lipids,
carbohydrates, proteins, and nucleic acids. These are essential for all living
organisms.
5. Which subatomic particle has a positive charge and is located in the
nucleus?
A) Electron
B) Neutron
C) Proton
D) Positron
Correct Answer: C
Rationale: Protons are positively charged particles found in the nucleus of an
atom. Electrons are negatively charged and orbit the nucleus, while neutrons
have no charge.
, 6. What is the primary function of carbohydrates in living organisms?
A) Genetic information storage
B) Energy storage and structural support
C) Catalyzing chemical reactions
D) Forming cell membranes
Correct Answer: B
Rationale: Carbohydrates primarily serve as energy sources (glucose) and
structural components (cellulose, chitin). They are not the primary genetic
material, catalysts, or membrane formers.
7. Which type of lipid is the main component of cell membranes?
A) Triglycerides
B) Steroids
C) Phospholipids
D) Waxes
Correct Answer: C
Rationale: Phospholipids are the primary structural component of cell
membranes, forming a bilayer. Triglycerides store energy, steroids include
hormones, and waxes provide waterproofing.
