JAMB Past Questions

Biology 2025

40 free JAMB Biology 2025 questions with correct answers and explanations.

Practice this set

Q1.What is the primary function of the C3 cycle in photosynthesis?

  • To fix CO2 into glucose
  • B.To regenerate RuBP
  • C.To produce ATP and NADPH
  • D.To synthesize proteins

Explanation: The C3 cycle (Calvin cycle) fixes CO2 into a 3-carbon compound, eventually forming glucose using ATP and NADPH.

Q2.Which enzyme is responsible for unwinding DNA during replication?

  • Helicase
  • B.Polymerase
  • C.Ligase
  • D.Restriction endonuclease

Explanation: Helicase unwinds the DNA double helix by breaking hydrogen bonds, enabling replication.

Q3.What is the role of the sarcoplasmic reticulum in muscle contraction?

  • To release calcium ions
  • B.To regulate muscle tone
  • C.To synthesize ATP
  • D.To store glycogen

Explanation: The sarcoplasmic reticulum releases calcium ions to trigger muscle contraction by enabling actin-myosin interactions.

Q4.Which type of cell signaling involves the release of signaling molecules into the bloodstream?

  • Endocrine signaling
  • B.Paracrine signaling
  • C.Autocrine signaling
  • D.Juxtacrine signaling

Explanation: Endocrine signaling uses hormones released into the bloodstream to target distant cells.

Q5.What is the function of the Casparian strip in plant roots?

  • A.To regulate water uptake
  • To control mineral absorption
  • C.To synthesize suberin
  • D.To facilitate gas exchange

Explanation: The Casparian strip in the endodermis controls mineral absorption by forcing selective uptake through cell membranes.

Q6.Which part of the brain regulates the body's circadian rhythms?

  • Suprachiasmatic nucleus
  • B.Hypothalamus
  • C.Thalamus
  • D.Cerebral cortex

Explanation: The suprachiasmatic nucleus (SCN) in the hypothalamus regulates circadian rhythms based on light cues.

Q7.What is the term for the process by which cells become specialized to perform specific functions?

  • Differentiation
  • B.Morphogenesis
  • C.Histogenesis
  • D.Organogenesis

Explanation: Differentiation is the process where cells specialize to perform specific roles, like nerve or muscle cells.

Q8.Which type of ecological interaction involves the competition for resources between different species?

  • A.Predation
  • Competition
  • C.Mutualism
  • D.Commensalism

Explanation: Competition occurs when species vie for limited resources, limiting each other’s growth.

Q9.What is the function of the proton pump in plant cells?

  • A.To regulate pH levels
  • B.To generate ATP
  • To transport ions
  • D.To synthesize proteins

Explanation: The proton pump transports protons (H+) across membranes, driving ion and nutrient uptake.

Q10.Which organelle is responsible for the degradation of proteins and organelles?

  • Lysosome
  • B.Proteasome
  • C.Peroxisome
  • D.Golgi apparatus

Explanation: Lysosomes use hydrolytic enzymes to degrade proteins, organelles, and cellular waste.

Q11.What is the term for the process by which organisms adapt to their environment through genetic changes?

  • Evolution
  • B.Natural selection
  • C.Adaptation
  • D.Mutation

Explanation: Evolution involves genetic changes over generations, driven by mechanisms like natural selection.

Q12.Which type of muscle fiber is characterized by a high concentration of myoglobin?

  • A.Fast-twitch fibers
  • Slow-twitch fibers
  • C.Intermediate fibers
  • D.Smooth muscle fibers

Explanation: Slow-twitch fibers, rich in myoglobin, store oxygen for endurance activities.

Q13.What is the function of the HMG-CoA reductase enzyme in cholesterol synthesis?

  • To catalyze the conversion of HMG-CoA to mevalonate
  • B.To regulate gene expression for cholesterol synthesis
  • C.To transport cholesterol in the bloodstream
  • D.To synthesize bile acids

Explanation: HMG-CoA reductase catalyzes the rate-limiting step of converting HMG-CoA to mevalonate in cholesterol synthesis.

Q14.Which part of the nephron is responsible for the reabsorption of glucose and amino acids?

  • Proximal convoluted tubule
  • B.Loop of Henle
  • C.Distal convoluted tubule
  • D.Collecting duct

Explanation: The proximal convoluted tubule reabsorbs glucose and amino acids from the filtrate.

Q15.What is the term for the process by which the body's immune system responds to pathogens?

  • Immune response
  • B.Inflammation
  • C.Phagocytosis
  • D.Immunological tolerance

Explanation: The immune response involves innate and adaptive immunity to combat pathogens.

Q16.Which type of cell junction is characterized by the presence of connexons?

  • A.Tight junctions
  • B.Adherens junctions
  • Gap junctions
  • D.Desmosomes

Explanation: Gap junctions use connexons to allow ion and small molecule passage between cells.

Q17.What is the function of the enzyme RuBisCO in the Calvin cycle?

  • To fix CO2 into a 3-carbon compound
  • B.To regenerate RuBP
  • C.To produce ATP and NADPH
  • D.To synthesize proteins

Explanation: RuBisCO fixes CO2 into 3-phosphoglycerate (3-PGA), a 3-carbon compound, in the Calvin cycle.

Q18.Which part of the brain regulates the body's emotional responses?

  • Amygdala
  • B.Hippocampus
  • C.Cerebral cortex
  • D.Brainstem

Explanation: The amygdala regulates emotions like fear and pleasure and is key in emotional memory.

Q19.What is the term for the process by which cells become resistant to antibiotics?

  • A.Mutation
  • B.Gene expression
  • C.Horizontal gene transfer
  • Natural selection

Explanation: Natural selection favors bacteria with resistance genes, allowing them to survive and reproduce.

Q20.Which type of ecological interaction involves one organism benefiting while the other is neither harmed nor benefited?

  • A.Predation
  • B.Competition
  • C.Mutualism
  • Commensalism

Explanation: Commensalism involves one organism benefiting while the other is unaffected, e.g., barnacles on whales.

Q21.What is the function of the enzyme DNA polymerase in DNA replication?

  • A.To unwind DNA
  • To synthesize new DNA strands
  • C.To repair damaged DNA
  • D.To cut DNA

Explanation: DNA polymerase adds nucleotides to synthesize new DNA strands based on the template strand.

Q22.Which part of the plant cell is responsible for the synthesis of cellulose?

  • A.Golgi apparatus
  • B.Endoplasmic reticulum
  • Plasma membrane
  • D.Cell wall

Explanation: The plasma membrane houses cellulose synthase enzymes that produce cellulose for the cell wall.

Q23.What is the term for the process by which the body's immune system remembers specific pathogens?

  • Immunological memory
  • B.Immune response
  • C.Inflammation
  • D.Phagocytosis

Explanation: Immunological memory enables faster immune responses upon re-exposure to pathogens.

Q24.Which type of muscle fiber is most susceptible to fatigue?

  • Fast-twitch fibers
  • B.Slow-twitch fibers
  • C.Intermediate fibers
  • D.Smooth muscle fibers

Explanation: Fast-twitch fibers rely on anaerobic respiration, leading to rapid fatigue from lactic acid buildup.

Q25.What is the function of the sinoatrial node in the heart?

  • To regulate heart rate
  • B.To control blood pressure
  • C.To pump blood
  • D.To filter blood

Explanation: The sinoatrial node, the heart’s pacemaker, generates impulses to regulate heart rate.

Q26.Which part of the nephron is responsible for the concentration of urine?

  • A.Proximal convoluted tubule
  • Loop of Henle
  • C.Distal convoluted tubule
  • D.Collecting duct

Explanation: The Loop of Henle creates a concentration gradient, enabling urine concentration via water reabsorption.

Q27.What is the term for the process by which cells communicate with each other through chemical signals?

  • Cell signaling
  • B.Cell division
  • C.Cell differentiation
  • D.Cell adhesion

Explanation: Cell signaling uses chemical signals like hormones to coordinate cellular activities.

Q28.Which type of ecological interaction involves one organism living on or in another and benefiting at its expense?

  • Parasitism
  • B.Predation
  • C.Competition
  • D.Mutualism

Explanation: Parasitism involves a parasite benefiting at the host’s expense, e.g., tapeworms in humans.

Q29.What is the function of the enzyme lactase in the small intestine?

  • To break down lactose into glucose and galactose
  • B.To synthesize lactose from glucose and galactose
  • C.To regulate blood sugar levels
  • D.To absorb lactose

Explanation: Lactase hydrolyzes lactose into glucose and galactose for absorption in the small intestine.

Q30.Which part of the brain regulates the body's appetite and satiety?

  • Hypothalamus
  • B.Thalamus
  • C.Cerebral cortex
  • D.Brainstem

Explanation: The hypothalamus regulates appetite and satiety by responding to hunger hormones like ghrelin and leptin.

Q31.What is the term for the process by which the body's immune system responds to allergens?

  • Allergic reaction
  • B.Immune response
  • C.Inflammation
  • D.Immunological tolerance

Explanation: An allergic reaction is a hypersensitive immune response to allergens, involving histamine release.

Q32.Which type of cell junction is responsible for maintaining tissue structure?

  • A.Tight junctions
  • B.Adherens junctions
  • C.Gap junctions
  • Desmosomes

Explanation: Desmosomes anchor cells, providing structural support in tissues like skin.

Q33.What is the function of the enzyme pyruvate kinase in glycolysis?

  • To convert phosphoenolpyruvate to pyruvate
  • B.To convert glucose to glucose-6-phosphate
  • C.To regulate glycolysis
  • D.To synthesize ATP

Explanation: Pyruvate kinase catalyzes the conversion of phosphoenolpyruvate to pyruvate, producing ATP in glycolysis.

Q34.Which part of the plant cell is responsible for the synthesis of starch?

  • A.Chloroplast
  • Amyloplast
  • C.Golgi apparatus
  • D.Endoplasmic reticulum

Explanation: Amyloplasts synthesize and store starch in plant storage organs like roots and tubers.

Q35.What is the term for the process by which cells become specialized to respond to specific stimuli?

  • Differentiation
  • B.Sensitization
  • C.Adaptation
  • D.Irritability

Explanation: Differentiation enables cells to specialize for functions like responding to stimuli, e.g., nerve cells.

Q36.Which type of muscle is characterized by the presence of intercalated discs?

  • A.Skeletal muscle
  • B.Smooth muscle
  • Cardiac muscle
  • D.Striated muscle

Explanation: Cardiac muscle has intercalated discs for rapid electrical communication, enabling coordinated contractions.

Q37.What is the function of the enzyme acetylcholinesterase in the nervous system?

  • A.To synthesize acetylcholine
  • To break down acetylcholine
  • C.To regulate muscle contraction
  • D.To transmit nerve impulses

Explanation: Acetylcholinesterase degrades acetylcholine in the synaptic cleft to terminate neural signals.

Q38.Which hormone is responsible for regulating the body's sleep-wake cycle?

  • Melatonin
  • B.Cortisol
  • C.Adrenaline
  • D.Thyroxine

Explanation: Melatonin, produced by the pineal gland, signals sleep in response to darkness, regulating the sleep-wake cycle.

Q39.Which type of immunity involves the production of antibodies to fight pathogens?

  • A.Cell-mediated immunity
  • Humoral immunity
  • C.Innate immunity
  • D.Passive immunity

Explanation: Humoral immunity involves B cells producing antibodies to target pathogens.

Q40.Which ecological interaction involves two organisms benefiting from each other?

  • Mutualism
  • B.Commensalism
  • C.Parasitism
  • D.Predation

Explanation: Mutualism benefits both organisms, e.g., bees pollinating flowers while feeding on nectar.

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