Bio 101 Test 1 Full Study Guide |Questions & Correct
Answers with Detailed Rationales | New 2026–2027
Update
1. About 25 of the 92 natural elements are known to be essential to life. Which 4
of these 25 make up 96% of living matter?
A. carbon, hydrogen, nitrogen, oxygen
B. carbon, sodium, chlorine, oxygen
C. hydrogen, helium, oxygen, nitrogen
D. carbon, calcium, phosphorus, sulfur
Correct Answer: A
Expert Rationale: Carbon, hydrogen, nitrogen, and oxygen are the four most
abundant elements in living matter.
2. Knowing just the whole number of an element allows inferences about which of
the following?
A. the number of protons plus neutrons in the element
B. the number of electrons only
C. the number of protons only
D. the number of neutrons only
Correct Answer: A
Expert Rationale: The mass number is the whole number and equals protons plus
neutrons.
,3. When two atoms have the same level of attraction for electrons, the type of
interaction between these two atoms can be described as
A. nonpolar covalent bond
B. polar covalent bond
C. ionic bond
D. hydrogen bond
Correct Answer: A
Expert Rationale: Equal electron sharing produces a nonpolar covalent bond.
4. What is the difference between covalent bonds and ionic bonds?
A. Covalent bonds involve the sharing of electrons between atoms; ionic bonds
involve the electrical attraction between atoms of opposite charge
B. Covalent bonds involve transfer of electrons; ionic bonds involve sharing of
electrons
C. Covalent bonds occur only in water; ionic bonds occur only in salts
D. Covalent bonds are weaker than ionic bonds in all cases
Correct Answer: A
Expert Rationale: Covalent bonds share electrons; ionic bonds attract oppositely
charged ions.
5. The element present in all organic molecules is
A. carbon
B. oxygen
C. nitrogen
D. hydrogen
Correct Answer: A
, Expert Rationale: Carbon is the central element in organic molecules.
6. A carbon atom is most likely to form which of the following bonds with other
atoms?
A. Covalent bonds
B. Ionic bonds
C. Hydrogen bonds
D. Metallic bonds
Correct Answer: A
Expert Rationale: Carbon readily forms covalent bonds by sharing electrons.
7. Which two functional groups are always found in amino acids?
A. carboxyl and amino
B. hydroxyl and carbonyl
C. sulfhydryl and phosphate
D. methyl and carbonyl
Correct Answer: A
Expert Rationale: Amino acids always contain a carboxyl group and an amino
group.
8. Which of the following is NOT a correct monomer/polymer pairing defining a
macromolecule?
A. Amino acid/DNA
B. Nucleotide/DNA
C. Monosaccharide/starch
Answers with Detailed Rationales | New 2026–2027
Update
1. About 25 of the 92 natural elements are known to be essential to life. Which 4
of these 25 make up 96% of living matter?
A. carbon, hydrogen, nitrogen, oxygen
B. carbon, sodium, chlorine, oxygen
C. hydrogen, helium, oxygen, nitrogen
D. carbon, calcium, phosphorus, sulfur
Correct Answer: A
Expert Rationale: Carbon, hydrogen, nitrogen, and oxygen are the four most
abundant elements in living matter.
2. Knowing just the whole number of an element allows inferences about which of
the following?
A. the number of protons plus neutrons in the element
B. the number of electrons only
C. the number of protons only
D. the number of neutrons only
Correct Answer: A
Expert Rationale: The mass number is the whole number and equals protons plus
neutrons.
,3. When two atoms have the same level of attraction for electrons, the type of
interaction between these two atoms can be described as
A. nonpolar covalent bond
B. polar covalent bond
C. ionic bond
D. hydrogen bond
Correct Answer: A
Expert Rationale: Equal electron sharing produces a nonpolar covalent bond.
4. What is the difference between covalent bonds and ionic bonds?
A. Covalent bonds involve the sharing of electrons between atoms; ionic bonds
involve the electrical attraction between atoms of opposite charge
B. Covalent bonds involve transfer of electrons; ionic bonds involve sharing of
electrons
C. Covalent bonds occur only in water; ionic bonds occur only in salts
D. Covalent bonds are weaker than ionic bonds in all cases
Correct Answer: A
Expert Rationale: Covalent bonds share electrons; ionic bonds attract oppositely
charged ions.
5. The element present in all organic molecules is
A. carbon
B. oxygen
C. nitrogen
D. hydrogen
Correct Answer: A
, Expert Rationale: Carbon is the central element in organic molecules.
6. A carbon atom is most likely to form which of the following bonds with other
atoms?
A. Covalent bonds
B. Ionic bonds
C. Hydrogen bonds
D. Metallic bonds
Correct Answer: A
Expert Rationale: Carbon readily forms covalent bonds by sharing electrons.
7. Which two functional groups are always found in amino acids?
A. carboxyl and amino
B. hydroxyl and carbonyl
C. sulfhydryl and phosphate
D. methyl and carbonyl
Correct Answer: A
Expert Rationale: Amino acids always contain a carboxyl group and an amino
group.
8. Which of the following is NOT a correct monomer/polymer pairing defining a
macromolecule?
A. Amino acid/DNA
B. Nucleotide/DNA
C. Monosaccharide/starch
