, Chapter 1: Life
Matching
A) Phylogenetic
B) q/T
C) Carbon
D) ΔH°
E) H – TS
F) halobacteria
G) equilibrium
H) entropy
I) thermoacidophiles
J) polymers
1. The most abundant chemical element in the human body is .
Ans: C
Level of Difficulty: Easy
Section: 1-5. The Origin of Life
2. Evolutionary relationships can be compared using a tree.
Ans: A
Level of Difficulty: Easy
Section: 1-2. Eukaryotes
3. The organisms most likely to be found in a brine solution would be .
Ans: F
Level of Difficulty: Easy
Section: 1-1. Prokaryotes
4. The organisms most likely to be found in high temperature environments would be .
Ans: I
, Level of Difficulty: Easy
Section: 1-1. Prokaryotes
6. Which statement best explains why carbon is uniquely suited as the backbone of biological
macromolecules?
A. Carbon forms only single covalent bonds
B. Carbon readily forms ionic bonds in aqueous environments
C. Carbon can form stable covalent bonds with itself and many other elements
D. Carbon has the highest electronegativity among biological elements
E. Carbon bonds are weaker than hydrogen bonds
Ans: C
Rationale:
Carbon’s ability to form four stable covalent bonds, including C–C bonds, allows for the formation of complex,
diverse, and stable molecular structures such as carbohydrates, proteins, lipids, and nucleic acids. This versatility is
unmatched by other elements in biological systems.
7. The Miller–Urey experiment provided experimental support for which major hypothesis?
A. Endosymbiotic theory
B. RNA world hypothesis
C. Abiotic synthesis of organic molecules
D. Natural selection
E. Directed panspermia
Ans: C
Rationale:
The Miller–Urey experiment demonstrated that organic molecules (e.g., amino acids) could form abiotically under
conditions thought to resemble early Earth’s atmosphere, supporting chemical evolution theories.
8. Which property of water most directly contributes to the stabilization of protein tertiary
structure?
A. High vapor pressure
B. High heat capacity
C. Hydrogen bonding and hydrophobic interactions
D. Low density in solid form
E. High ionization constant
Ans: C
, Rationale:
Protein folding is driven largely by hydrogen bonding and hydrophobic interactions, both of which are consequences
of water’s polarity and ability to form extensive hydrogen-bonding networks.
9. Living organisms are classified as thermodynamically open systems because they:
A. Exist in a constant state of equilibrium
B. Exchange both energy and matter with their surroundings
C. Obey different thermodynamic laws
D. Continuously decrease entropy
E. Do not require external energy sources
Ans: B
Rationale:
Living systems maintain order by importing energy and matter and exporting entropy to their surroundings, consistent
with the second law of thermodynamics.
10. Which feature most clearly distinguishes archaea from bacteria at the molecular level?
A. Presence of ribosomes
B. Lack of cell walls
C. Ether-linked membrane lipids
D. Circular DNA
E. Absence of metabolic pathways
Ans: C
Rationale:
Archaea possess ether-linked membrane lipids, unlike bacteria and eukaryotes, which have ester-linked lipids. This
contributes to archaeal survival in extreme environments.
11. A spontaneous biochemical reaction is best defined as one that:
A. Occurs rapidly
B. Requires enzymes
C. Has a negative ΔG
D. Releases heat
E. Occurs only at equilibrium
Ans: C
Rationale:
A reaction is spontaneous if ΔG < 0, meaning it can proceed without external energy input, regardless of reaction speed.
Matching
A) Phylogenetic
B) q/T
C) Carbon
D) ΔH°
E) H – TS
F) halobacteria
G) equilibrium
H) entropy
I) thermoacidophiles
J) polymers
1. The most abundant chemical element in the human body is .
Ans: C
Level of Difficulty: Easy
Section: 1-5. The Origin of Life
2. Evolutionary relationships can be compared using a tree.
Ans: A
Level of Difficulty: Easy
Section: 1-2. Eukaryotes
3. The organisms most likely to be found in a brine solution would be .
Ans: F
Level of Difficulty: Easy
Section: 1-1. Prokaryotes
4. The organisms most likely to be found in high temperature environments would be .
Ans: I
, Level of Difficulty: Easy
Section: 1-1. Prokaryotes
6. Which statement best explains why carbon is uniquely suited as the backbone of biological
macromolecules?
A. Carbon forms only single covalent bonds
B. Carbon readily forms ionic bonds in aqueous environments
C. Carbon can form stable covalent bonds with itself and many other elements
D. Carbon has the highest electronegativity among biological elements
E. Carbon bonds are weaker than hydrogen bonds
Ans: C
Rationale:
Carbon’s ability to form four stable covalent bonds, including C–C bonds, allows for the formation of complex,
diverse, and stable molecular structures such as carbohydrates, proteins, lipids, and nucleic acids. This versatility is
unmatched by other elements in biological systems.
7. The Miller–Urey experiment provided experimental support for which major hypothesis?
A. Endosymbiotic theory
B. RNA world hypothesis
C. Abiotic synthesis of organic molecules
D. Natural selection
E. Directed panspermia
Ans: C
Rationale:
The Miller–Urey experiment demonstrated that organic molecules (e.g., amino acids) could form abiotically under
conditions thought to resemble early Earth’s atmosphere, supporting chemical evolution theories.
8. Which property of water most directly contributes to the stabilization of protein tertiary
structure?
A. High vapor pressure
B. High heat capacity
C. Hydrogen bonding and hydrophobic interactions
D. Low density in solid form
E. High ionization constant
Ans: C
, Rationale:
Protein folding is driven largely by hydrogen bonding and hydrophobic interactions, both of which are consequences
of water’s polarity and ability to form extensive hydrogen-bonding networks.
9. Living organisms are classified as thermodynamically open systems because they:
A. Exist in a constant state of equilibrium
B. Exchange both energy and matter with their surroundings
C. Obey different thermodynamic laws
D. Continuously decrease entropy
E. Do not require external energy sources
Ans: B
Rationale:
Living systems maintain order by importing energy and matter and exporting entropy to their surroundings, consistent
with the second law of thermodynamics.
10. Which feature most clearly distinguishes archaea from bacteria at the molecular level?
A. Presence of ribosomes
B. Lack of cell walls
C. Ether-linked membrane lipids
D. Circular DNA
E. Absence of metabolic pathways
Ans: C
Rationale:
Archaea possess ether-linked membrane lipids, unlike bacteria and eukaryotes, which have ester-linked lipids. This
contributes to archaeal survival in extreme environments.
11. A spontaneous biochemical reaction is best defined as one that:
A. Occurs rapidly
B. Requires enzymes
C. Has a negative ΔG
D. Releases heat
E. Occurs only at equilibrium
Ans: C
Rationale:
A reaction is spontaneous if ΔG < 0, meaning it can proceed without external energy input, regardless of reaction speed.
