MCAT BIOLOGICAL AND BIOCHEMICAL FOUNDATIONS
OF LIVING SYSTEMS (BBLS) NEWEST 2025-2026 UPDATE
REAL PRACTICE EXAM QUESTIONS & CORRECT
ANSWERS | ALREADY GRADED A+
Content covered (most frequently tested topics):
Cell biology, membranes and transport, enzymes and kinetics,
metabolism (glycolysis, TCA cycle, ETC), molecular genetics,
DNA replication, transcription and translation, protein
structure, amino acids, hormones and signaling, nervous
system basics, immune system basics, microbiology,
biotechnology techniques, evolution and population genetics,
physiology integration.
1. Which organelle is primarily responsible for oxidative phosphorylation in
eukaryotic cells?
A. Nucleus
B. Mitochondrion
C. Lysosome
D. Golgi apparatus
Answer: B. Mitochondrion
Oxidative phosphorylation occurs in the inner mitochondrial membrane where
the electron transport chain and ATP synthase are located. The proton gradient
generated across this membrane drives ATP synthesis.
2. Which level of protein structure is stabilized primarily by hydrogen bonds
between backbone atoms?
,A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Answer: B. Secondary
Secondary structure refers to alpha helices and beta sheets formed through
hydrogen bonding between backbone amide hydrogen and carbonyl oxygen
atoms.
3. Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate
in the first step of glycolysis?
A. Hexokinase
B. Pyruvate kinase
C. Aldolase
D. Lactate dehydrogenase
Answer: A. Hexokinase
Hexokinase phosphorylates glucose using ATP to form glucose-6-phosphate,
trapping glucose inside the cell.
4. Which amino acid contains a sulfur atom in its side chain?
A. Valine
B. Serine
C. Cysteine
D. Glycine
Answer: C. Cysteine
Cysteine contains a thiol (-SH) group which can form disulfide bonds important for
stabilizing protein tertiary structure.
5. Which molecule acts as the final electron acceptor in the electron transport
chain during aerobic respiration?
,A. NAD+
B. Oxygen
C. Carbon dioxide
D. ATP
Answer: B. Oxygen
Oxygen accepts electrons and protons at the end of the electron transport chain
forming water.
6. Which process produces the greatest amount of ATP per molecule of
glucose?
A. Glycolysis
B. Citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Answer: C. Oxidative phosphorylation
The majority of ATP during cellular respiration is produced via oxidative
phosphorylation through the proton gradient generated by the electron transport
chain.
7. What type of membrane transport requires ATP directly?
A. Facilitated diffusion
B. Osmosis
C. Primary active transport
D. Passive diffusion
Answer: C. Primary active transport
Primary active transport uses ATP hydrolysis to move substances against their
concentration gradients.
8. During DNA replication, which enzyme synthesizes RNA primers?
A. Primase
B. DNA polymerase III
, C. Helicase
D. Ligase
Answer: A. Primase
Primase synthesizes short RNA primers that provide a free 3′ hydroxyl group for
DNA polymerase to extend.
9. Which phase of mitosis is characterized by alignment of chromosomes at
the metaphase plate?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer: B. Metaphase
During metaphase chromosomes line up along the cell’s equatorial plane before
sister chromatids separate.
10.Which macromolecule stores genetic information?
A. Protein
B. Lipid
C. DNA
D. Carbohydrate
Answer: C. DNA
DNA stores hereditary information through sequences of nucleotides.
11.Which structure is responsible for protein synthesis?
A. Ribosome
B. Lysosome
C. Peroxisome
D. Centrosome
Answer: A. Ribosome
OF LIVING SYSTEMS (BBLS) NEWEST 2025-2026 UPDATE
REAL PRACTICE EXAM QUESTIONS & CORRECT
ANSWERS | ALREADY GRADED A+
Content covered (most frequently tested topics):
Cell biology, membranes and transport, enzymes and kinetics,
metabolism (glycolysis, TCA cycle, ETC), molecular genetics,
DNA replication, transcription and translation, protein
structure, amino acids, hormones and signaling, nervous
system basics, immune system basics, microbiology,
biotechnology techniques, evolution and population genetics,
physiology integration.
1. Which organelle is primarily responsible for oxidative phosphorylation in
eukaryotic cells?
A. Nucleus
B. Mitochondrion
C. Lysosome
D. Golgi apparatus
Answer: B. Mitochondrion
Oxidative phosphorylation occurs in the inner mitochondrial membrane where
the electron transport chain and ATP synthase are located. The proton gradient
generated across this membrane drives ATP synthesis.
2. Which level of protein structure is stabilized primarily by hydrogen bonds
between backbone atoms?
,A. Primary
B. Secondary
C. Tertiary
D. Quaternary
Answer: B. Secondary
Secondary structure refers to alpha helices and beta sheets formed through
hydrogen bonding between backbone amide hydrogen and carbonyl oxygen
atoms.
3. Which enzyme catalyzes the conversion of glucose to glucose-6-phosphate
in the first step of glycolysis?
A. Hexokinase
B. Pyruvate kinase
C. Aldolase
D. Lactate dehydrogenase
Answer: A. Hexokinase
Hexokinase phosphorylates glucose using ATP to form glucose-6-phosphate,
trapping glucose inside the cell.
4. Which amino acid contains a sulfur atom in its side chain?
A. Valine
B. Serine
C. Cysteine
D. Glycine
Answer: C. Cysteine
Cysteine contains a thiol (-SH) group which can form disulfide bonds important for
stabilizing protein tertiary structure.
5. Which molecule acts as the final electron acceptor in the electron transport
chain during aerobic respiration?
,A. NAD+
B. Oxygen
C. Carbon dioxide
D. ATP
Answer: B. Oxygen
Oxygen accepts electrons and protons at the end of the electron transport chain
forming water.
6. Which process produces the greatest amount of ATP per molecule of
glucose?
A. Glycolysis
B. Citric acid cycle
C. Oxidative phosphorylation
D. Fermentation
Answer: C. Oxidative phosphorylation
The majority of ATP during cellular respiration is produced via oxidative
phosphorylation through the proton gradient generated by the electron transport
chain.
7. What type of membrane transport requires ATP directly?
A. Facilitated diffusion
B. Osmosis
C. Primary active transport
D. Passive diffusion
Answer: C. Primary active transport
Primary active transport uses ATP hydrolysis to move substances against their
concentration gradients.
8. During DNA replication, which enzyme synthesizes RNA primers?
A. Primase
B. DNA polymerase III
, C. Helicase
D. Ligase
Answer: A. Primase
Primase synthesizes short RNA primers that provide a free 3′ hydroxyl group for
DNA polymerase to extend.
9. Which phase of mitosis is characterized by alignment of chromosomes at
the metaphase plate?
A. Prophase
B. Metaphase
C. Anaphase
D. Telophase
Answer: B. Metaphase
During metaphase chromosomes line up along the cell’s equatorial plane before
sister chromatids separate.
10.Which macromolecule stores genetic information?
A. Protein
B. Lipid
C. DNA
D. Carbohydrate
Answer: C. DNA
DNA stores hereditary information through sequences of nucleotides.
11.Which structure is responsible for protein synthesis?
A. Ribosome
B. Lysosome
C. Peroxisome
D. Centrosome
Answer: A. Ribosome
