SCIN138 Week 8 Final Exam | Fully Solved |
Guaranteed Grade A+
1. Which organelle is primarily responsible for ATP production in eukaryotic cells?
A. Golgi apparatus
B. Lysosome
C. Mitochondrion
D. Endoplasmic reticulum
Explanation: Mitochondria perform oxidative phosphorylation and the citric acid cycle
to produce ATP, the cell’s main energy currency; they have inner membrane folds
(cristae) that increase surface area for ATP synthase activity.
2. Water's high specific heat is important for living organisms because it:
A. Causes water to evaporate quickly
B. Helps buffer temperature changes in cells and environments
C. Lowers the pH of aquatic systems
D. Makes water a poor solvent
Explanation: High specific heat means water absorbs/releases large heat with small
temperature change, stabilizing internal temperatures of organisms and microclimate
conditions—critical for enzyme stability and physiological homeostasis.
3. In a titration, the equivalence point is reached when:
A. The indicator changes color slightly
B. The moles of acid equal the moles of base (stoichiometrically)
C. pH = 7 always
D. The solution becomes saturated
Explanation: The equivalence point occurs when stoichiometric amounts of titrant and
analyte have reacted; pH at equivalence depends on acid/base strengths, and an
indicator is chosen to approximate this point.
4. Which gas law relates pressure and volume of a gas at constant temperature?
A. Charles’s law
B. Boyle’s law
C. Avogadro’s law
D. Gay-Lussac’s law
Explanation: Boyle’s law states that pressure is inversely proportional to volume for a
, fixed amount of gas at constant temperature (P ∝ 1/V); experimentally shown by
isothermal compression/expansion.
5. Natural selection acts on:
A. Genotypes only
B. Phenotypes only
C. Allele frequencies without phenotypic effect
D. Mutations in somatic cells only
Explanation: Natural selection favors phenotypes that improve reproductive success;
phenotypes arise from genotype + environment, and selection changes allele
frequencies by differential reproductive success of phenotypic variants.
6. The primary structural component of plant cell walls is:
A. Chitin
B. Cellulose
C. Collagen
D. Glycogen
Explanation: Plant cell walls are mainly composed of cellulose — long β-1,4 glucose
polymers forming microfibrils that provide rigidity and tensile strength to plant tissues.
7. A solution has [H⁺] = 1 × 10⁻⁵ M. Its pH is:
A. 5
B. 9
C. 10
D. 3
Explanation: pH is the negative base-10 logarithm of hydrogen ion concentration: pH =
−log[H⁺] = −log(1×10⁻⁵) = 5; this indicates a mildly acidic solution.
8. Which bond is strongest under physiological conditions?
A. Hydrogen bond
B. Ionic bond in water
C. Covalent bond
D. Van der Waals interaction
Explanation: Covalent bonds involve sharing electron pairs between atoms and are far
stronger (higher bond energies) than hydrogen bonds, ionic interactions in polar
solvents, or weak dispersion forces.
9. In Mendelian inheritance, crossing two heterozygotes (Aa × Aa) for a single gene gives
genotype ratio:
A. 1 AA : 2 Aa : 1 aa
, B. 3 AA : 1 aa
C. 1 AA : 1 aa
D. 2 AA : 2 Aa : 0 aa
Explanation: Classic Mendelian monohybrid cross yields a 1:2:1 genotype ratio (AA : Aa :
aa), reflecting segregation of alleles during gamete formation.
10. Enzymes increase reaction rates by:
A. Raising the activation energy
B. Lowering the activation energy
C. Changing the equilibrium constant
D. Being consumed in the reaction
Explanation: Enzymes are biological catalysts that lower activation energy through
transition state stabilization, increasing reaction rate while not altering the equilibrium
position; they remain unchanged after reaction.
11. Which electromagnetic wave has the highest energy per photon?
A. Radio waves
B. Visible light
C. X-rays
D. Infrared
Explanation: Photon energy is proportional to frequency; X-rays have much higher
frequency than visible or infrared and thus higher photon energy, which explains their
penetrating ability and ionizing effects.
12. The basic unit of heredity is the:
A. Chromosome
B. Nucleotide
C. Gene
D. Ribosome
Explanation: A gene is a DNA segment encoding functional product (RNA or protein);
chromosomes carry many genes, nucleotides are building blocks, and ribosomes
translate mRNA into protein.
13. Osmosis refers to net movement of water across a semipermeable membrane from:
A. Low solute concentration to high solute concentration
B. High solute concentration to low solute concentration
C. Low water concentration to high water concentration
D. Areas of positive charge to negative charge
Explanation: Osmosis is diffusion of solvent (water) toward higher solute concentration
Guaranteed Grade A+
1. Which organelle is primarily responsible for ATP production in eukaryotic cells?
A. Golgi apparatus
B. Lysosome
C. Mitochondrion
D. Endoplasmic reticulum
Explanation: Mitochondria perform oxidative phosphorylation and the citric acid cycle
to produce ATP, the cell’s main energy currency; they have inner membrane folds
(cristae) that increase surface area for ATP synthase activity.
2. Water's high specific heat is important for living organisms because it:
A. Causes water to evaporate quickly
B. Helps buffer temperature changes in cells and environments
C. Lowers the pH of aquatic systems
D. Makes water a poor solvent
Explanation: High specific heat means water absorbs/releases large heat with small
temperature change, stabilizing internal temperatures of organisms and microclimate
conditions—critical for enzyme stability and physiological homeostasis.
3. In a titration, the equivalence point is reached when:
A. The indicator changes color slightly
B. The moles of acid equal the moles of base (stoichiometrically)
C. pH = 7 always
D. The solution becomes saturated
Explanation: The equivalence point occurs when stoichiometric amounts of titrant and
analyte have reacted; pH at equivalence depends on acid/base strengths, and an
indicator is chosen to approximate this point.
4. Which gas law relates pressure and volume of a gas at constant temperature?
A. Charles’s law
B. Boyle’s law
C. Avogadro’s law
D. Gay-Lussac’s law
Explanation: Boyle’s law states that pressure is inversely proportional to volume for a
, fixed amount of gas at constant temperature (P ∝ 1/V); experimentally shown by
isothermal compression/expansion.
5. Natural selection acts on:
A. Genotypes only
B. Phenotypes only
C. Allele frequencies without phenotypic effect
D. Mutations in somatic cells only
Explanation: Natural selection favors phenotypes that improve reproductive success;
phenotypes arise from genotype + environment, and selection changes allele
frequencies by differential reproductive success of phenotypic variants.
6. The primary structural component of plant cell walls is:
A. Chitin
B. Cellulose
C. Collagen
D. Glycogen
Explanation: Plant cell walls are mainly composed of cellulose — long β-1,4 glucose
polymers forming microfibrils that provide rigidity and tensile strength to plant tissues.
7. A solution has [H⁺] = 1 × 10⁻⁵ M. Its pH is:
A. 5
B. 9
C. 10
D. 3
Explanation: pH is the negative base-10 logarithm of hydrogen ion concentration: pH =
−log[H⁺] = −log(1×10⁻⁵) = 5; this indicates a mildly acidic solution.
8. Which bond is strongest under physiological conditions?
A. Hydrogen bond
B. Ionic bond in water
C. Covalent bond
D. Van der Waals interaction
Explanation: Covalent bonds involve sharing electron pairs between atoms and are far
stronger (higher bond energies) than hydrogen bonds, ionic interactions in polar
solvents, or weak dispersion forces.
9. In Mendelian inheritance, crossing two heterozygotes (Aa × Aa) for a single gene gives
genotype ratio:
A. 1 AA : 2 Aa : 1 aa
, B. 3 AA : 1 aa
C. 1 AA : 1 aa
D. 2 AA : 2 Aa : 0 aa
Explanation: Classic Mendelian monohybrid cross yields a 1:2:1 genotype ratio (AA : Aa :
aa), reflecting segregation of alleles during gamete formation.
10. Enzymes increase reaction rates by:
A. Raising the activation energy
B. Lowering the activation energy
C. Changing the equilibrium constant
D. Being consumed in the reaction
Explanation: Enzymes are biological catalysts that lower activation energy through
transition state stabilization, increasing reaction rate while not altering the equilibrium
position; they remain unchanged after reaction.
11. Which electromagnetic wave has the highest energy per photon?
A. Radio waves
B. Visible light
C. X-rays
D. Infrared
Explanation: Photon energy is proportional to frequency; X-rays have much higher
frequency than visible or infrared and thus higher photon energy, which explains their
penetrating ability and ionizing effects.
12. The basic unit of heredity is the:
A. Chromosome
B. Nucleotide
C. Gene
D. Ribosome
Explanation: A gene is a DNA segment encoding functional product (RNA or protein);
chromosomes carry many genes, nucleotides are building blocks, and ribosomes
translate mRNA into protein.
13. Osmosis refers to net movement of water across a semipermeable membrane from:
A. Low solute concentration to high solute concentration
B. High solute concentration to low solute concentration
C. Low water concentration to high water concentration
D. Areas of positive charge to negative charge
Explanation: Osmosis is diffusion of solvent (water) toward higher solute concentration
