Question 1 of 10
Which molecule carries energy from glucose breakdown to the electron transport chain?
AATP
BNADH
CH2O
DCO2
Explanation
📌 NADH and FADH2 are electron carriers. They transport high-energy electrons from glycolysis and Krebs cycle to the ETC.
Question 2 of 10
Which organelle is labeled X in the cell diagram below? 
AEndoplasmic reticulum
BNucleus
CMitochondria
DGolgi apparatus
Explanation
📌 Organelle X has the bean-shaped structure with inner folds (cristae) → Mitochondria
Mitochondria = powerhouse of the cell = produces ATP through cellular respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Mitochondria = powerhouse of the cell = produces ATP through cellular respiration
C₆H₁₂O₆ + 6O₂ → 6CO₂ + 6H₂O + ATP
Question 3 of 10
A theory in science is:
Aa proven fact that can never change
Ban untested guess
Cthe same as a hypothesis
Da well-supported explanation based on extensive evidence
Explanation
📌 A scientific theory is well-tested, widely accepted, and explains a broad range of observations.
It is NOT just a guess — that's a hypothesis.
It is NOT just a guess — that's a hypothesis.
Question 4 of 10
The graph shows the change in a moth population over time. Dark moths increased after industrial pollution darkened tree bark. This is an example of:
AGenetic engineering
BNatural selection
CArtificial selection
DSpontaneous generation
Explanation
📌 This is the classic peppered moth example of natural selection.
Before pollution: light bark → light moths camouflaged → survived
After pollution: dark bark → dark moths camouflaged → survived
The environment selected for the trait that provided camouflage.
Before pollution: light bark → light moths camouflaged → survived
After pollution: dark bark → dark moths camouflaged → survived
The environment selected for the trait that provided camouflage.
Question 5 of 10
All three domains of life (Bacteria, Archaea, and Eukarya) share which structural feature?
AMulticellular organization
BChloroplasts for photosynthesis
CA membrane-bound nucleus
DRibosomes for protein synthesis
Explanation
All cellular life — Bacteria, Archaea, and Eukarya — uses ribosomes to build proteins. Distractors: a membrane-bound nucleus is found only in Eukarya (Bacteria and Archaea are prokaryotic). Multicellularity appears only in some Eukarya — most life is unicellular. Chloroplasts are organelles found only in plants and algae (a subset of Eukarya).
Question 6 of 10
Which class of biomolecule is built from nucleotide monomers?
AProteins
BLipids
CCarbohydrates
DNucleic acids (DNA and RNA)
Explanation
Nucleic acids (DNA, RNA) are polymers of nucleotide monomers — each nucleotide is a phosphate + sugar + nitrogenous base. Distractors: Proteins are polymers of *amino acids*. Carbohydrates are polymers of *monosaccharides* (e.g., glucose). Lipids are not true polymers — they assemble from fatty acids and glycerol but don't repeat a single monomer.
Question 7 of 10
The Hardy-Weinberg principle states that allele frequencies remain constant when:
Athere is no evolution occurring
Bnatural selection is strong
Cthe population is very small
Dmutations are common
Explanation
📌 Conditions: no mutation, no migration, random mating, large population, no natural selection.
Any violation → evolution occurs.
Any violation → evolution occurs.
Question 8 of 10
In the food web below, what would happen if all the frogs were removed? 
AInsect population increases and snake population decreases
BAll organisms die
CSnake population increases
DNothing changes
Explanation
📌 If frogs are removed:
• Insects (grasshoppers) they ate would INCREASE (no predator)
• Snakes that ate frogs would DECREASE (less food)
• This demonstrates how removing one species affects the entire food web.
• Insects (grasshoppers) they ate would INCREASE (no predator)
• Snakes that ate frogs would DECREASE (less food)
• This demonstrates how removing one species affects the entire food web.
Question 9 of 10
Use the Punnett square to determine the probability of offspring with the homozygous recessive (aa) genotype.
A1/2 (50%)
B3/4 (75%)
C1/4 (25%)
D0
Explanation
Aa × Aa cross: AA, Aa, Aa, aa. Only one box (aa) shows the homozygous recessive: 1/4 = 25%.
Question 10 of 10
In a Punnett square cross Bb × Bb, what fraction of offspring are expected to be homozygous recessive (bb)?
A0%
B25%
C50%
D75%
Explanation
📌 BB:Bb:bb = 1:2:1
bb = 1/4 = 25%
bb = 1/4 = 25%