BIOL180 Unit Test 3 Biomolecules and
Enzymes Questions And Correct
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Rationales 2026 Q&A | Instant
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1. Which statement best describes a biological molecule?
A. A substance found only in inorganic materials
B. A molecule produced exclusively by animals
C. A substance that cannot contain carbon
D. A molecule involved in the structure or function of living
organisms
Answer: D. A molecule involved in the structure or function of living
organisms
Rationale: Biological molecules, or biomolecules, are chemical
compounds that participate in the structure, organization, metabolism,
regulation, and functioning of living systems. Major classes include
carbohydrates, lipids, proteins, and nucleic acids.
2. Which four elements make up most of the mass of living
organisms?
A. Carbon, hydrogen, oxygen, and nitrogen
B. Sodium, potassium, calcium, and chlorine
C. Iron, copper, zinc, and magnesium
D. Phosphorus, sulfur, sodium, and iodine
Answer: A. Carbon, hydrogen, oxygen, and nitrogen
,Rationale: Carbon, hydrogen, oxygen, and nitrogen are the four major
elements found in biological molecules. Carbon is particularly
important because it can form four covalent bonds and create complex
molecular structures.
3. Why is carbon especially important in biological molecules?
A. Carbon can form only one bond.
B. Carbon can form four covalent bonds and create diverse
molecular structures.
C. Carbon is always positively charged in cells.
D. Carbon cannot bond with other carbon atoms.
Answer: B. Carbon can form four covalent bonds and create diverse
molecular structures.
Rationale: Carbon's ability to form four stable covalent bonds allows it
to form chains, branches, rings, and complex three-dimensional
structures. This versatility makes carbon the central element of
organic chemistry and biomolecules.
4. What is a functional group?
A. A complete biological organism
B. A group of identical cells
C. A specific group of atoms that gives a molecule characteristic
chemical properties
D. A type of cellular organelle
Answer: C. A specific group of atoms that gives a molecule
characteristic chemical properties
Rationale: Functional groups are specific arrangements of atoms
attached to carbon skeletons. Examples include hydroxyl, carbonyl,
,carboxyl, amino, phosphate, and sulfhydryl groups. They strongly
influence a molecule's chemical behavior.
5. Which functional group is represented by –OH?
A. Carbonyl
B. Amino
C. Carboxyl
D. Hydroxyl
Answer: D. Hydroxyl
Rationale: The hydroxyl group consists of an oxygen atom bonded to a
hydrogen atom. Molecules containing hydroxyl groups are often polar
because oxygen attracts electrons strongly. Alcohols commonly
contain hydroxyl groups.
6. Which functional group is characteristic of amino acids and
contains nitrogen?
A. Amino
B. Hydroxyl
C. Carbonyl
D. Phosphate
Answer: A. Amino
Rationale: The amino group contains nitrogen and is commonly
represented as –NH₂. In many biological conditions, it can accept a
proton and become positively charged as –NH₃⁺. Amino groups are
characteristic components of amino acids.
7. Which functional group contains a carbon atom double-bonded to
oxygen?
, A. Phosphate
B. Hydroxyl
C. Carbonyl
D. Sulfhydryl
Answer: C. Carbonyl
Rationale: A carbonyl group contains a carbon atom double-bonded to
oxygen. Carbonyls occur in aldehydes and ketones and contribute
significantly to the chemical properties of carbohydrates and other
organic molecules.
8. Which functional group is represented by –COOH?
A. Amino
B. Carboxyl
C. Hydroxyl
D. Sulfhydryl
Answer: B. Carboxyl
Rationale: A carboxyl group contains both a carbonyl and hydroxyl
group. It can donate a proton, making molecules containing carboxyl
groups acidic. Amino acids contain carboxyl groups.
9. What is a polymer?
A. A large molecule composed of repeating smaller subunits
B. A single atom
C. An inorganic salt
D. A type of enzyme inhibitor
Answer: A. A large molecule composed of repeating smaller subunits
Rationale: Polymers are large molecules built from repeating units
called monomers. Proteins, nucleic acids, and many carbohydrates are
Enzymes Questions And Correct
Answers (Verified Answers) Plus
Rationales 2026 Q&A | Instant
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1. Which statement best describes a biological molecule?
A. A substance found only in inorganic materials
B. A molecule produced exclusively by animals
C. A substance that cannot contain carbon
D. A molecule involved in the structure or function of living
organisms
Answer: D. A molecule involved in the structure or function of living
organisms
Rationale: Biological molecules, or biomolecules, are chemical
compounds that participate in the structure, organization, metabolism,
regulation, and functioning of living systems. Major classes include
carbohydrates, lipids, proteins, and nucleic acids.
2. Which four elements make up most of the mass of living
organisms?
A. Carbon, hydrogen, oxygen, and nitrogen
B. Sodium, potassium, calcium, and chlorine
C. Iron, copper, zinc, and magnesium
D. Phosphorus, sulfur, sodium, and iodine
Answer: A. Carbon, hydrogen, oxygen, and nitrogen
,Rationale: Carbon, hydrogen, oxygen, and nitrogen are the four major
elements found in biological molecules. Carbon is particularly
important because it can form four covalent bonds and create complex
molecular structures.
3. Why is carbon especially important in biological molecules?
A. Carbon can form only one bond.
B. Carbon can form four covalent bonds and create diverse
molecular structures.
C. Carbon is always positively charged in cells.
D. Carbon cannot bond with other carbon atoms.
Answer: B. Carbon can form four covalent bonds and create diverse
molecular structures.
Rationale: Carbon's ability to form four stable covalent bonds allows it
to form chains, branches, rings, and complex three-dimensional
structures. This versatility makes carbon the central element of
organic chemistry and biomolecules.
4. What is a functional group?
A. A complete biological organism
B. A group of identical cells
C. A specific group of atoms that gives a molecule characteristic
chemical properties
D. A type of cellular organelle
Answer: C. A specific group of atoms that gives a molecule
characteristic chemical properties
Rationale: Functional groups are specific arrangements of atoms
attached to carbon skeletons. Examples include hydroxyl, carbonyl,
,carboxyl, amino, phosphate, and sulfhydryl groups. They strongly
influence a molecule's chemical behavior.
5. Which functional group is represented by –OH?
A. Carbonyl
B. Amino
C. Carboxyl
D. Hydroxyl
Answer: D. Hydroxyl
Rationale: The hydroxyl group consists of an oxygen atom bonded to a
hydrogen atom. Molecules containing hydroxyl groups are often polar
because oxygen attracts electrons strongly. Alcohols commonly
contain hydroxyl groups.
6. Which functional group is characteristic of amino acids and
contains nitrogen?
A. Amino
B. Hydroxyl
C. Carbonyl
D. Phosphate
Answer: A. Amino
Rationale: The amino group contains nitrogen and is commonly
represented as –NH₂. In many biological conditions, it can accept a
proton and become positively charged as –NH₃⁺. Amino groups are
characteristic components of amino acids.
7. Which functional group contains a carbon atom double-bonded to
oxygen?
, A. Phosphate
B. Hydroxyl
C. Carbonyl
D. Sulfhydryl
Answer: C. Carbonyl
Rationale: A carbonyl group contains a carbon atom double-bonded to
oxygen. Carbonyls occur in aldehydes and ketones and contribute
significantly to the chemical properties of carbohydrates and other
organic molecules.
8. Which functional group is represented by –COOH?
A. Amino
B. Carboxyl
C. Hydroxyl
D. Sulfhydryl
Answer: B. Carboxyl
Rationale: A carboxyl group contains both a carbonyl and hydroxyl
group. It can donate a proton, making molecules containing carboxyl
groups acidic. Amino acids contain carboxyl groups.
9. What is a polymer?
A. A large molecule composed of repeating smaller subunits
B. A single atom
C. An inorganic salt
D. A type of enzyme inhibitor
Answer: A. A large molecule composed of repeating smaller subunits
Rationale: Polymers are large molecules built from repeating units
called monomers. Proteins, nucleic acids, and many carbohydrates are
