Biology & Life Sciences
2 MAXE · 171 OIB
◆ ◆
Department of Cellular & Molecular Biology
BIOLOGY
EXPLORING THE SCIENCE OF LIFE
BIO 171 Exam 2 — Cellular Biology & Biochemistry
CO M P R E H E N S I V E E X A M I N AT I O N : C E L L ST R U CT U R E · M E M B RA N E T RA N S P O RT ·
E N ZY M E S · C E L LU L A R R E S P I RAT I O N · P H OTO SY N T H E S I S
INSTITUTION [UNCONFIRMED] — BIO 171 COURSE CODE BIO 171
General Biology
PROGRAM [INFERRED] — Associate / ACADEMIC YEAR
Bachelor of Science
EXAM TITLE BIO 171 Exam 2 — Cellular Biology TOTAL QUESTIONS 100 Questions
& Biochemistry
COURSE TITLE General Biology II — Cell & FORMAT Multiple Choice — Select the
Molecular Biology Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question based on BIO 171 Exam 2 content.
▸ Questions cover cell structure, membrane transport, enzymes, cellular respiration, and photosynthesis.
▸ Correct answers and detailed rationales provided for comprehensive exam preparation.
, SECTION I — BIO 171 EXAM 2: CELLULAR BIOLOGY &
Questions 1 – 100
BIOCHEMISTRY
1. What happens when a cell is placed in a hypotonic solution?
A. Water moves out of the cell, causing it to shrivel
B. Water moves into the cell — round, balloon-looking cells result (solution hypotonic, cell
hypertonic)
C. No net movement of water; cell maintains its shape
D. Solutes move into the cell while water moves out equally
CORRECT ANSWER B — Water moves into the cell — round, balloon-looking cells result
(solution hypotonic, cell hypertonic)
RATIONALE In a hypotonic solution, the extracellular solute concentration is lower than inside
the cell — meaning the extracellular water concentration is higher. Water moves
by osmosis from an area of higher water concentration (outside) to lower water
concentration (inside). The cell swells and appears round and balloon-like. In
animal cells, this can lead to lysis (bursting) if the osmotic gradient is severe. In
plant cells, the rigid cell wall prevents bursting — instead, the cell becomes turgid,
which is actually the ideal state for plant cells. This is why plant cells prefer a
hypotonic environment: the turgor pressure against the cell wall provides
structural support.
,2. What types of molecules move across the membrane via passive diffusion?
A. All molecules regardless of size or charge
B. Hydrophobic or small uncharged polar molecules (lipids, CO₂, O₂, H₂O)
C. Large hydrophilic molecules and ions only
D. Only water molecules through aquaporins
CORRECT ANSWER B — Hydrophobic or small uncharged polar molecules (lipids, CO₂, O₂, H₂O)
RATIONALE Passive diffusion occurs directly through the phospholipid bilayer without
requiring membrane proteins. Molecules that can diffuse this way share two
characteristics: (1) They are hydrophobic (nonpolar) — like lipids, steroid
hormones, and O₂ — allowing them to dissolve through the hydrophobic core of
the membrane; (2) They are small and uncharged — like water (H₂O) and carbon
dioxide (CO₂). Large polar molecules (glucose), charged ions (Na⁺, K⁺, Cl⁻), and
hydrophilic molecules cannot pass directly through the hydrophobic membrane
interior — they require facilitated diffusion through channel or carrier proteins.
Passive diffusion does not require energy (ATP) and moves substances DOWN
their concentration gradient (high to low concentration).
, 3. What does the endosymbiotic theory explain?
A. How DNA replication produces identical copies during cell division
B. How infolding of the plasma membrane gave rise to endomembrane components
(nucleus, ER, etc.)
C. How proteins are synthesized from mRNA at ribosomes
D. How enzymes lower activation energy to speed up reactions
CORRECT ANSWER B — How infolding of the plasma membrane gave rise to endomembrane
components (nucleus, ER, etc.)
RATIONALE The endosymbiotic theory explains the origin of eukaryotic organelles through
two mechanisms: (1) Infolding of the ancestral prokaryote's plasma membrane
gave rise to the endomembrane system — including the nuclear envelope,
endoplasmic reticulum, Golgi apparatus, and other internal membranes. (2)
Endosymbiosis — an ancestral eukaryote engulfed aerobic bacteria (alpha-
proteobacteria) that evolved into mitochondria (1st symbiotic event), and later
engulfed photosynthetic bacteria (cyanobacteria) that evolved into chloroplasts
(2nd event). Evidence includes: double membranes around these organelles, their
own circular DNA and ribosomes (similar to bacteria), and division by binary
fission. This theory explains the compartmentalization that defines eukaryotic
cells.
2 MAXE · 171 OIB
◆ ◆
Department of Cellular & Molecular Biology
BIOLOGY
EXPLORING THE SCIENCE OF LIFE
BIO 171 Exam 2 — Cellular Biology & Biochemistry
CO M P R E H E N S I V E E X A M I N AT I O N : C E L L ST R U CT U R E · M E M B RA N E T RA N S P O RT ·
E N ZY M E S · C E L LU L A R R E S P I RAT I O N · P H OTO SY N T H E S I S
INSTITUTION [UNCONFIRMED] — BIO 171 COURSE CODE BIO 171
General Biology
PROGRAM [INFERRED] — Associate / ACADEMIC YEAR
Bachelor of Science
EXAM TITLE BIO 171 Exam 2 — Cellular Biology TOTAL QUESTIONS 100 Questions
& Biochemistry
COURSE TITLE General Biology II — Cell & FORMAT Multiple Choice — Select the
Molecular Biology Single Best Answer
EXAMINATION INSTRUCTIONS
▸ Select the single best answer for each question based on BIO 171 Exam 2 content.
▸ Questions cover cell structure, membrane transport, enzymes, cellular respiration, and photosynthesis.
▸ Correct answers and detailed rationales provided for comprehensive exam preparation.
, SECTION I — BIO 171 EXAM 2: CELLULAR BIOLOGY &
Questions 1 – 100
BIOCHEMISTRY
1. What happens when a cell is placed in a hypotonic solution?
A. Water moves out of the cell, causing it to shrivel
B. Water moves into the cell — round, balloon-looking cells result (solution hypotonic, cell
hypertonic)
C. No net movement of water; cell maintains its shape
D. Solutes move into the cell while water moves out equally
CORRECT ANSWER B — Water moves into the cell — round, balloon-looking cells result
(solution hypotonic, cell hypertonic)
RATIONALE In a hypotonic solution, the extracellular solute concentration is lower than inside
the cell — meaning the extracellular water concentration is higher. Water moves
by osmosis from an area of higher water concentration (outside) to lower water
concentration (inside). The cell swells and appears round and balloon-like. In
animal cells, this can lead to lysis (bursting) if the osmotic gradient is severe. In
plant cells, the rigid cell wall prevents bursting — instead, the cell becomes turgid,
which is actually the ideal state for plant cells. This is why plant cells prefer a
hypotonic environment: the turgor pressure against the cell wall provides
structural support.
,2. What types of molecules move across the membrane via passive diffusion?
A. All molecules regardless of size or charge
B. Hydrophobic or small uncharged polar molecules (lipids, CO₂, O₂, H₂O)
C. Large hydrophilic molecules and ions only
D. Only water molecules through aquaporins
CORRECT ANSWER B — Hydrophobic or small uncharged polar molecules (lipids, CO₂, O₂, H₂O)
RATIONALE Passive diffusion occurs directly through the phospholipid bilayer without
requiring membrane proteins. Molecules that can diffuse this way share two
characteristics: (1) They are hydrophobic (nonpolar) — like lipids, steroid
hormones, and O₂ — allowing them to dissolve through the hydrophobic core of
the membrane; (2) They are small and uncharged — like water (H₂O) and carbon
dioxide (CO₂). Large polar molecules (glucose), charged ions (Na⁺, K⁺, Cl⁻), and
hydrophilic molecules cannot pass directly through the hydrophobic membrane
interior — they require facilitated diffusion through channel or carrier proteins.
Passive diffusion does not require energy (ATP) and moves substances DOWN
their concentration gradient (high to low concentration).
, 3. What does the endosymbiotic theory explain?
A. How DNA replication produces identical copies during cell division
B. How infolding of the plasma membrane gave rise to endomembrane components
(nucleus, ER, etc.)
C. How proteins are synthesized from mRNA at ribosomes
D. How enzymes lower activation energy to speed up reactions
CORRECT ANSWER B — How infolding of the plasma membrane gave rise to endomembrane
components (nucleus, ER, etc.)
RATIONALE The endosymbiotic theory explains the origin of eukaryotic organelles through
two mechanisms: (1) Infolding of the ancestral prokaryote's plasma membrane
gave rise to the endomembrane system — including the nuclear envelope,
endoplasmic reticulum, Golgi apparatus, and other internal membranes. (2)
Endosymbiosis — an ancestral eukaryote engulfed aerobic bacteria (alpha-
proteobacteria) that evolved into mitochondria (1st symbiotic event), and later
engulfed photosynthetic bacteria (cyanobacteria) that evolved into chloroplasts
(2nd event). Evidence includes: double membranes around these organelles, their
own circular DNA and ribosomes (similar to bacteria), and division by binary
fission. This theory explains the compartmentalization that defines eukaryotic
cells.
