Question 1 of 10
Which molecule carries energy from glucose breakdown to the electron transport chain?
AATP
BNADH
CCO2
DH2O
Explanation
📌 NADH and FADH2 are electron carriers. They transport high-energy electrons from glycolysis and Krebs cycle to the ETC.
Question 2 of 10
During which phase of the cell cycle does DNA replication occur? 
AG1 phase
BG2 phase
CS phase
DM phase
Explanation
📌 DNA replication occurs during S phase (Synthesis) of interphase.
Interphase: G1 → S → G2, then Mitosis.
Interphase: G1 → S → G2, then Mitosis.
Question 3 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:
ANatural selection
BArtificial selection
CGenetic engineering
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 4 of 10
Which organelle is labeled X in the cell diagram below? 
ANucleus
BMitochondria
CGolgi apparatus
DEndoplasmic reticulum
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 5 of 10
All three domains of life (Bacteria, Archaea, and Eukarya) share which structural feature?
ARibosomes for protein synthesis
BA membrane-bound nucleus
CChloroplasts for photosynthesis
DMulticellular organization
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
The Hardy-Weinberg principle states that allele frequencies remain constant when:
Athere is no evolution occurring
Bthe population is very small
Cnatural selection is strong
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 7 of 10
A theory in science is:
Aa well-supported explanation based on extensive evidence
Ban untested guess
Cthe same as a hypothesis
Da proven fact that can never change
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 8 of 10
A student designed an experiment to test how light affects plant growth. Identify the components of this experiment. 
AIndependent: plant height; Dependent: light
BIndependent: water; Dependent: soil
CIndependent: temperature; Dependent: light
DIndependent: light; Dependent: plant height
Explanation
📌 Independent variable = what you change (light)
Dependent variable = what you measure (plant height)
Control group = no light (to compare against)
Constants = same soil, water, temperature, pot size
Dependent variable = what you measure (plant height)
Control group = no light (to compare against)
Constants = same soil, water, temperature, pot size
Question 9 of 10
In a DNA nucleotide, which component carries the genetic code through its specific sequence?
APhosphate group
BNitrogenous base
CHydrogen bond
DDeoxyribose sugar
Explanation
The nitrogenous base (adenine, thymine, guanine, or cytosine) is the part of a DNA nucleotide that varies — its sequence along the strand IS the genetic code. The phosphate and deoxyribose sugar are identical in every nucleotide and form the structural 'backbone' of the DNA strand; they don't store information. Hydrogen bonds hold the two strands together at the bases but are not part of a single nucleotide.
Question 10 of 10
Which graph correctly shows exponential growth?
AA
BNeither
CBoth
DB
Explanation
📌 Exponential growth = J-shaped curve (slow start, rapid increase)
Linear growth = straight line (constant rate)
Graph A shows exponential growth.
Linear growth = straight line (constant rate)
Graph A shows exponential growth.